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voltage drops big time with ac Pages: 12Last

pippo on Mon August 23, 2010 7:52 PM User is offline

People,

I have an 87 alfa spider. Need advice on this problem: Whenever I turn on ac with car running, voltmeter drops from about 14v to 12, also, it affects bigtime the speedometer to the point that i even got speeding tickets cuz erroneous velocity indicated. Most times, with car off, when I go to start it with ac switch on the car wont even turn over-nothing. I have to turn ac switch OFF then the car starts.

Been living with this for years so finally decided to ask you people. I heard of a voltage drop test. would this be helpful here or other approach?

Thanks, guys.

pip

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emsvitil on Tue August 24, 2010 12:45 AM User is offlineView users profile

Test the amp draw of the clutch coil.



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Ed
SoCal

pippo on Tue August 24, 2010 8:17 PM User is offline

Quote
Originally posted by: emsvitil
Test the amp draw of the clutch coil.

Thanks, ems, but if you can maybe send along maybe stepwise method I would appreciate it. Now, I take it you mean the compressor clutch. I put meter on current and touch blk/red terminals to where?

Thanks!

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mk378 on Tue August 24, 2010 8:47 PM User is offline

A voltage drop test is just to go through each part of the circuit (switch, connection, relay, fuse box, etc.) and see where voltage is being lost. Obtain a schematic of the car and identify parts of the circuit starting from the clutch and working back to the battery. Start the engine and A/C then measure the voltage across each part. Set your meter on volts and put one probe on each side of the component under test. With a digital meter it doesn't matter which probe you use where, you may measure a positive or negative voltage but it should be low. An ideal part would have zero volts drop. If you are at less than 1 volt total across all parts that is probably OK. The test must be conducted with current flowing, i.e. the system in operation.

Don't forget the ground side of the circuit too. Measure voltage from both the frame and the engine to battery minus. It should be very close to zero. Bad grounds cause a lot of general electrical malaise.

ACProf on Tue August 24, 2010 8:53 PM User is offline

If you put the meter on current and then touch the red and black probes to power, you will blow the fuse in the meter.

VOLTAGE is measured the way you just described, by putting the meter leads ACROSS a voltge source, + and -.

CURRENT is measured IN THE CIRCUIT flow. You have to BREAK open the circuit somewhere, and then put the meter in between the break, one lead one on each end of the break. If the value comes up (-), reverse the leads. Make sure the meter is set correctly to the 10 AMPS scale and the lead is plugged into the 10 AMP jack.

Current reading with clutch energized should be 3 to 4 AMPS. If the coil is shorted, it may pull over 10 AMPS and blow the fuse in the meter.







Edited: Tue August 24, 2010 at 8:55 PM by ACProf

newton5 on Wed August 25, 2010 12:46 AM User is offlineView users profile

Have you verified the integrity of all of the vehicle grounds?
Have you verified that the voltage is really dropping that much by testing right at the battery?

With the low voltage reading (assuming on the inst panel volt gauge), inaccurate speedometer, and the no-crank issue only with the AC turned on, it sounds like you could have a body/chassis ground issue. Poor grounds can cause all manner of odd problems as current seeks a path to ground through various components.
Having driven a 1988 Lincoln Mark VII for 5 years, I'm very familiar with ground issues. Your description sounds strangely familiar.

mk378's voltage drop test can spot a ground issue if you know what to look for. If you're unfamiliar with voltage drop testing, then just locating, cleaning and securing ALL of the ground points on the car may solve the problem. It can be tedious, but it's pretty easy and free.

Good Luck pippo

Rick-l on Wed August 25, 2010 2:00 PM User is offline

you could put your voltmeter on the battery to see if the system voltage is really dropping from 14 to 12 or if it is just the voltage across the meter in the dash dropping (due to a bad ground).

If the battery voltage is dropping (unlikely) your AC either causes the alternator to cease functioning or there is a massive current draw.

pippo on Wed August 25, 2010 5:35 PM User is offline

Wow, so much info/feedback! Thanks, guys. Now this is something I can dive into. I do have to read these posts a few times to really understand what I am going to do, and I dont want to blow any fuses. Time to study.........

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bohica2xo on Wed August 25, 2010 7:48 PM User is offline

Start with the DVM connected directly to the battery. Measure the voltage, and record it:

1) At rest. Before you start the engine or turn on any accessories. Preferably after sitting overnight.

2) With the engine running at idle, no accessories switched on.

3) With the A/C system switched on, engine still at idle.

4) With the A/C system still on, engine speed above 1500 rpm.

Start with the basics. Actual battery voltage, and charging system performance. Post the results, and we can go from there.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

pippo on Thu August 26, 2010 3:27 PM User is offline

Quote
Originally posted by: bohica2xo
Start with the DVM connected directly to the battery. Measure the voltage, and record it:



1) At rest. Before you start the engine or turn on any accessories. Preferably after sitting overnight.



2) With the engine running at idle, no accessories switched on.



3) With the A/C system switched on, engine still at idle.



4) With the A/C system still on, engine speed above 1500 rpm.



Start with the basics. Actual battery voltage, and charging system performance. Post the results, and we can go from there.



B.

OK...this gives me a simple stepwise plan. Thanks a million, bohica, and others too.......Im gonnna figure this out if its the last thing I do........cant take it anymore.


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pippo on Sat August 28, 2010 2:48 PM User is offline

Finally got it done, Bohica....... numbered as the above post:

1) 12.73v
2) 13.38v
3) 13.19v
4) also 13.19v (though, since I was alone, the only way to reach about 1500 rpm AND ckeck at bettery was to rev by using "choke"/auxilliary air valve)

So, wondering what these results say at face value, guys?

Thanks!

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bohica2xo on Sat August 28, 2010 5:46 PM User is offline

Possibly an open diode in the alternator. Or a bad regulator.

The battery voltage at rest indicates a battery that still has six good cells, but it is not getting much of a charge.

13.38v charge after starting is low, even at idle.

It goes downhill from there to 13.19 with a load, and does not increase at all with an increase in engine speed. I suspect with the addition of the headlights it will drop even farther.


That should be a 65 amp Bosch alternator with an internal regulator. A reputable shop should be able to bench test it for output.

If you can reach the output stud at the back of the alternator, check the voltage while idling. If it is not the same as the battery voltage at the battery terminal, post the voltage readings of both.

B.


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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

pippo on Sat August 28, 2010 8:50 PM User is offline

Quote
Originally posted by: bohica2xo
Possibly an open diode in the alternator. Or a bad regulator.



The battery voltage at rest indicates a battery that still has six good cells, but it is not getting much of a charge.



13.38v charge after starting is low, even at idle.



It goes downhill from there to 13.19 with a load, and does not increase at all with an increase in engine speed. I suspect with the addition of the headlights it will drop even farther.





That should be a 65 amp Bosch alternator with an internal regulator. A reputable shop should be able to bench test it for output.



If you can reach the output stud at the back of the alternator, check the voltage while idling. If it is not the same as the battery voltage at the battery terminal, post the voltage readings of both.



B.

Man, Bo, youre not gonna believe it, but last week, we put in a new alt AND a new battery!! Yeah, the alt was lifetime, and the old one apparently had a bad internal regulator. I dont know what going on. BTW, this happens with either new alts or 1-2 yr old ones. Now, tomorroew, Im gonna get voltage from the alt/battery junction box....dont know it that matters at thiis point, eh? Its real hard to get V at the terminal nut at the alt like you said.

Any thougts, Bo? Thanks big time for your support!

Pip



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ACProf on Sat August 28, 2010 11:29 PM User is offline

At about 1000+ RPM I'd expect to see 14.0 - 14.4V on the BATT stud on the rear of the alternator. Not much less than that at the battery terminals.

Do you have any service manual or wiring schematics for the charge system? (I know 87 was quite a while ago).

How many connections (other than the BATT) does the alternator have on it? Trying to determine what kind of charge circuit it has.
Does the car have an amp gauge or just a ALT light? If a light, does the ALT light come on when you first turn on the key?

Just Saying: On the back of DELCO units (I know for sure) there is a hole in the back of the case with a metal tab visible in the hole. If you put a metal screwdriver in the hole and touch the tab and the case together, it bypasses the internal regulator and runs the alternator "wide open". Don't know what kind of alt is in the Alfa.

bohica2xo on Sun August 29, 2010 2:51 AM User is offline

That Bosch unit was available with several regulator setpoints. Perhaps you are getting the one that tops out @ 14.1v max. Do NOT go poking in the back of it looking for a "full field" test - unless you want to use that warranty.

The good news is there are a couple of regulators you could swap into that unit. One is just the higher setpoint, and the second one is actually adjustable. Easy enough to change, and they are also the brush holder assembly.

WAI part numbers:

IB348 15v maximum voltage

IB370A Adjustable voltage

I would still be inclined to check the diodes, especially if I have the alternator out to swap regulators.

You may still have other issues like corroded connections in the power distribution system which cause voltage drops to the instrument panel. But the low charge voltage is not helping that sort of thing either. One thing at a time, starting with the battery....

Do you live someplace with a lot of corrosion issues? Is this car a daily driver, or does it sit all winter?

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Sun August 29, 2010 5:42 AM User is offline

I recently had a Paris-Rhone alternator apart that is very similar to Bosch alternators of this era, seems like these Europeans copy off of each other that was only outputting 13 V and at room temperature, should have been outputting 14.5 V.

Like most any other alternator, uses six main diodes, three positive and three negative, plus three more they call the diode trio, three smaller positive diodes that feed the field circuit through the voltage regulator. Whats different about these alternators is that the sense output is also connected to the output of the diode trio as opposed to a Delco 10SI with that 1-2 plug where pin 2 is the sense output that connects directly to the battery. Pin 1 is directly to the output of the diode trio that is used to excite the alternator when first started up where the Europeans call this the D+ terminal that also requires a startup voltage from the ignition switch as when the alternator is sitting idle, the diode trio outputs zero volts for the field/regulator circuit. No field voltage, alternator will never start up, although some when revved to 3,000 rpm have enough residual magnetism in the rotor core to start up on their own.

Doesn't take much to start them up, typically a #194 bulb is placed in series with the D+ lead that doubles as a BAT warning lamp. When the ignition is first turned on due to the low impedance of the D+ circuit to ground, lamp will ignite bright, but when the alternator starts up, the D+ voltage should equally equal the main diode output with zero volts across it. If any diode trio or main diode is opened, this lamp will glow dim. With no output of the diode trio, will glow bright.

Feel the reason why Bosch senses the the diode trio output, they didn't have me to show them how to design a high impedance input regulator, sucker pulls about 10 milliamps that if it sensed the battery directly like they should, would discharge your battery when the car is sitting.

Anyway, pulled the rectifier assembly out by removing the three poorly soldered stator leads, checked all nine diodes, all were good, but typical poor rushed soldering of all nine diodes, that is 18 connections, resoldered those with lots of flux smoke. The regulator, way overpriced by the way, really overpriced is just a simple two transistor regulator, if the voltage is less than 14.5 V, it switches the field on, full, if above, switches it off with about a 20 mv hysteresis so it doesn't oscillate. It was connected to the field, ground and sense inputs via badly corroded spade lugs. Since I don't plan on unplugging the regulator every five minutes, cleaned and soldered those terminals. Did test the setpoint voltage on the regulator first, was at exactly 14.5 V, field terminal outputted full voltage when under 14.5 V and zero slightly above it.

Brushes were good, but the slip rings were a deep brown color, slapped that in my lath and polished them to a bright copper color, put it back together cleaning other corrosive elements like the BAT and internal ground connections and got out a full 14.5 V at the full rated current of 51 amperes. Also regreased the bearings when I had that apart, grease dries up in these things.

Didn't occur to me at the time, recently got a Volvo outdrive boat, actually never heard of Volvo, but learned they purchased what was left of OMC, and they use Prestolite and Paris-Rhoone alternators, really haven't heard of Bosch being used, but the same circuit. But they have learned the Delco 10SI fits perfectly just as well that are cheap here where these European replacements cost both arms and legs to replace. But tell them pin 1 on the Delco is D+ and pin 2 has to be wired directly to the positive post of the battery where it is wired internally on these other two way overpriced alternators.

Could be the same with Bosch, worth looking into. One thing I have noticed about these European alternators, their aluminum and copper is not nearly as good as what ours were back then. Was a b!tch to pull this Paris apart due to corrosion, and remembered the same thing with Bosch. But after a good cleaning, very easy to assemble. Gee I even have a couple of new 10SI's laying around here someplace, could have saved myself a bunch of work, but what the heck, kept it stock and working great again.

Corrosion adds to the internal source resistance, the more current you draw, the lower the output voltage, that simple. You just say your AC, what about your headlamps? Difference is going through the ignition switch, can also be the problem. Enjoyed taking apart the ignition switch on my 82 Chevy motorhome, we had some quality back then even though our sheet metal was pure crap. Making better sheet metal today, but our ignition switches today are pure crap. Never free of problems, if it isn't one thing, its another.

ACProf on Sun August 29, 2010 11:45 AM User is offline

Mr Nick, (off the topic completely, but I felt compelled to respond).

Thanks for the enlightening presentation about European alternators. It's apparent that "like an old tire, you've been around". I have rebuild a ton of alternators too, mostly Delco, because the reman's are expensive and typically only the bad part(s) were replaced. I've opened up a "new" reman only to see dried up, well used grease caked on the bearing grease shields with grungy slip rings and 50% used brushes. But the new sandblasted finish was clean!!!

Got a "SI" last month that was frustratingly intermittent. I examined everything and then found a rotor coil wire cold soldered to the binding post with a HUGE glob of solder. No quality in handwork now-a-days.

I've rebuilt the diodes on several terribly overpriced Toyota alternators. The diodes were actually just the die RTV'd in a metal dimple on the + and - busbars, with an accordioned whisker coming out the middle of the RTV. Pepboys used to sell a "Ford Alt rebuild kit" for $29.95. THe kit contained 6 75 AMP Motorola "button" diodes, new bearings, and brushes which didn't fit anythign else. THose diodes sold for over $6 each wholesale!!

I'd clean out the dimples and solder pot the button diodes in, solder on a piece of 16 ga. solid wire, put in the new bearings, and close it up. NEVER had a bad diode callback on those. The OEM was over $200, and the parts store sold new ones for about $160. I'd charge $70 for the whole job.

I have an Actron Auto Multimeter and I called them to ask about how the alternator diode test worked. He said they just capacitively coupled the DC output, and measured the ripple. The tech also sent me the schematic for meter! Since SPX bought 'em, I don't think that's likely to happen again!

Incidentally, I'm working with another engineer on "another" use for the Delco SI alternators. We put this same set up together on the "Ellen Degeneres Show" last year!!

Human Power

Have a good day, sir, (and don't let the smoke out of those ICs)!!


Edited: Sun August 29, 2010 at 1:22 PM by ACProf

bohica2xo on Sun August 29, 2010 1:10 PM User is offline

The bosch unit is internally sensed, there is no external sense terminal. One of the biggest problems with rebuilt 25 year old alternators is the lack of OEM parts. On many models the only regulator available to the rebuilder is chinese aftermarket garbage. Even some Delco parts are no longer available, and the asian knockoffs are all over the place for output.

I know someone that has replaced six HEI modules in two years, and there is nothing wrong with the balance of the system - I have been over the vehicle with a fine tooth comb myself. He finally sourced a module from a different supplier, and it seems to be ok. If you own a mid-90's Ford with TFI ignition, I would pick up an OEM module while they are still around...

Paris-Rhone, now there is some real junk. Valeo is not much better either. NipponDenso's Hairpin alternators are fantastic, and the older wirewound stuff was very high quality as well. Denso stuff all has welded diodes rather than soldered connections.

On vehicles fitted with that particular Bosch unit, I have found using a CS130 Delco to replace it solves the issues. The CS130 is a good unit, and has an external sense terminal. You will need to run a new 8 gauge wire to the battery positive from the output stud - euro cars had barely enough copper for the 60 amp alternator. There is a CS130 with the offset tension ear like the bosch unit. You will also need the harness plug for the CS130 type alternator (also fits the CS144). A small modification of the mounting spool is required, but a hacksaw & a file will do that easily.

The CS130 will put out more at idle than the Bosch did at 3000 rpm. The little 130 is a great replacement for SI's as well, it drops right in. Took me longer to splice the plug on a 1980 El Camino the other day than it did to put the alternator in.

The basic CS130, with SI type mounting:





The CS130 with offset tension ear, for replacing Bosch doorstops:




The plain old CS130 is the unit you want, with the boxy plug. There is a later unit, the CS130D - which has a plug with an oval shape, and no external fan. I am not as thrilled with that unit, it seems like they fail more often.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

pippo on Sun August 29, 2010 3:27 PM User is offline

Thanks, guys. So much good tech info......Yes, it is a bosch type, 65 amps. And, we have replaced these alts with new , all under lifetime, for years, and every time, still the same symptom: voltage suck down with ac on. Auto zone has been gracious about it all along. Still, something's not right.

I have added an extra heavy copper wire from alt to alt/batt junction box. Also, added a huge boat size wire from engine to body for extra ground. Dont see any difference, though. Now, back to the voltage drop test......is that idea relevant anymore given what we have to work with now, guys? Should I still perform a drop test? I mean, yeah, I did the simple voltage tests Bohica suggested, and we now have those results, but if yous still suggest it, I will be happy to do more, if at this point, it could deem useful.

Please understand that much of the above detailed/extended posts on alternators is beyond my expertise/understanding. I read them, but not sure what to do with the info. Thanks again, people. Still hopeful.........

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mk378 on Sun August 29, 2010 4:22 PM User is offline

Internal sensing means that the alternator doesn't compensate for drops in the wiring back to the battery.

Measure true alternator performance by measuring from the output terminal to engine ground. Since the terminal is hard to reach, put a test wire on it first before starting the engine, and connect that wire to your voltmeter. Be very careful not to short to ground. if it's less than 14 volts with the engine running (faster than idle), you need to replace and/or upgrade the alternator. If you have good voltage at the alternator, it's being lost on the way to the battery. Consider bypassing the fuse box and running the new output wire direct to battery.

Also do the ground test to make sure your grounds are really working: measure voltage difference between battery (-) and the engine and the body (two tests).

Edited: Sun August 29, 2010 at 4:24 PM by mk378

pippo on Sun August 29, 2010 6:45 PM User is offline

Quote
Originally posted by: mk378
Internal sensing means that the alternator doesn't compensate for drops in the wiring back to the battery.



Measure true alternator performance by measuring from the output terminal to engine ground. Since the terminal is hard to reach, put a test wire on it first before starting the engine, and connect that wire to your voltmeter. Be very careful not to short to ground. if it's less than 14 volts with the engine running (faster than idle), you need to replace and/or upgrade the alternator. If you have good voltage at the alternator, it's being lost on the way to the battery. Consider bypassing the fuse box and running the new output wire direct to battery.



Also do the ground test to make sure your grounds are really working: measure voltage difference between battery (-) and the engine and the body (two tests).

Thanks, MK. Now I get it. this is easy to do (once I set up the wire/wires. ). I understand how if the alt is charging 14+ but shows weaker farther down the line, its being lost elsewhere. And, it may be time to find a new source for its power (with fuse). Onward....the project goes on! I will be in touch!!

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pippo on Sun August 29, 2010 8:31 PM User is offline

Forgot.....so do I forget entirely about this "voltage drop test" and focus on what we discussed? (or is the above discussion a type of drop test)?

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fonebone on Mon August 30, 2010 1:33 AM User is offline

Great stuff here from all!! (Nickd-wish I lived closer to ya, would love to learn from the MASTER!) Hope no one minds the plug, but have dealt with the following site-highly recommended! Really gets into some interesting electrical issues along the same lines. Especially for pippo, check out "electrical tech" link at home page-the "one wire alternator" article gives you an excellent description of "remote sensing vs. internal sensing". http://www.madelectrical.com/index.shtml

Edited: Mon August 30, 2010 at 9:47 AM by fonebone

NickD on Mon August 30, 2010 8:57 AM User is offline

On the vehicle, would connect a voltmeter directly to the BAT and GND terminal to the alternator, run the engine 1,500 to 2,000 rpm and use a carbon pile load tester to approach the full output current capacity of the alternator to outrule that as the source of the problem. Voltage should hold to 14.5V at 25*C until the maximum capacity is hit, then drops off quickly. If that is okay, your problem is elsewhere. Can check your load currents to make sure they do not exceed the rating of the alternator.

Pease don't mention sandblasted alternator housings to me, also sandblast the rectifier seat that greatly affects the thermoconductivity overheating the rectifier diodes. When my company moved to China, was getting a lot of calls from our customers as where to buy decent parts, my company went to hell. I have no solutions for that.

A new alternator from Autozone? From what I have seen a bunch of old mixed parts all sandblasted and slapped together, excessive rotor to stator clearances. They grind out the stator so the rotor doesn't hit it because the rotor shaft is bend and use greaseless Chinese made bearings. Really can't call that new, Carquest is about the same. NAPA's premium line was made to OE specifications and looks like a new alternator. Not sure what they are doing now after some odd four years.

Still have some connections, and get get a nice core that I can rebuild myself. Original CS-130 used chip diodes with a 30 amp rating, not really desirable for a 105 amp alternator, but will be okay if you don't draw 105 amps for over a minute. I managed to swipe a couple of phorotype press fit rectifier assemblies with a 150 amp capacity, they will last. Again the bean counters. Discharged battery is the worse culprit, will take all the alternator can deliver, GM even recommends to fully charge the battery first when replacing this alternator. But what happens if a car is stuck at an airport for three weeks with all that added garbage that draws down the battery? Don't have to be concerned about anti-thief, damn battery is dead anyway.

Actually worked for a first tier supplier, a faction of cent over in unit cost made the difference between a large contract or zero. Besides dealing with the ERA, OSHA, and the EPA that don't give a damn about whether you were making a profit or not, the worse was the IRS wanting to value out the door prices on inventory. And inventory we had as the OE's insisted on JIT inventory. This value was part of the profit and they wouldn't take tax payments in alternator parts, wanted cold hard cash you didn't make yet.

I can't even express my hatred for our government, whole bunch should be hung as traitors to this once great country and giving all of our business to far east countries that gave us living hell in the past.

But I am in a bad mood now, not only did my property taxes go up 500 bucks last year for my same old home, got a letter that it was reassessed for 8% higher due to inflation when I just heard on the news that property values dropped the lowest in 30 years. Then to top that off, daughters college tuition payments increased by 1,400 bucks from last year. Claim all this money is going to Iraq and Afghanistan plus with unemployment so high, revenues are low. But they have to maintain their life style, screw the rest of us. Really don't blame my company for selling out to China, well aware of their fits as well.

In the meantime, scrounging all parts to keep my vehicles running so I have enough left over to pay tuition and taxes. If I don't pay property taxes, will auction off my home and kick me out on the street. So much for our caring leadership. And so much for bean counters and profiteers. A whole bunch of crooks in my opinion.

Sorry for the rant, but feel like I am not the only one.

fonebone on Mon August 30, 2010 12:29 PM User is offline

No apologies necessary nickd- For those of us up there in years, you are on target. As for the younger folk, you are talking in a foreign language.

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