Automotive Air Conditioning Information Forum (Archives)

pippo on Mon November 15, 2010 7:11 PM

Hi again, guys,

Man,just when you get caught up, bam, no ac. 87 Alfa Spider, was doing work around the stick shifter/console area, which required removal of the ac switch fro console face plate. No big deal.

Well, before I was getting cold air, after putting together the console, no ac. Figured it had to be some wire I missed, although, it was so simple a job, bnot involving wires to be disconnected, really, just "put aside". Well, I hooked up a guage and pressure showed 70 or so. But I learned on this forum from one of you guys last year, static psi doesnt mean much.....right?

So, compressor does not come on. Not sure what to do first. Tips appreciated as always.

Oh, it has R12.

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ice-n-tropics on Mon November 15, 2010 7:47 PM

If you have the Sanden SD508 compressor in a 87 Spider then you have my early version BEHR A/C under dash evaporator and maybe the optional auxilary condenser fan for hot ambients. The aux. fan circuit has a diode that will blow instantly if it sees reverse polarity. Does the aux fan run. If so then the diode is OK. Condenser fans free wheel due to ram air with the A/C off and can cause nuisance clutch engagement without a diode or relay.
Does the clutch engage?
The 4 speed fan uses 2 resistors and a relay combo to get 4 speeds. If the resistors operate w/o air flow their thermal sensor protector blows and doesn't reset.
The main 30 amp A/C circuit breaker resets automatically if it trips.
hotrodac


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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Mon November 15, 2010 at 7:51 PM by ice-n-tropics

pippo on Mon November 15, 2010 7:57 PM

Quote
Originally posted by: ice-n-tropics
If you have the Sanden SD508 compressor in a 87 Spider then you have my early version BEHR A/C under dash evaporator and maybe the optional auxilary condenser fan for hot ambients. The aux. fan circuit has a diode that will blow instantly if it sees reverse polarity. Does the aux fan run. If so then the diode is OK. Condenser fans free wheel due to ram air with the A/C off and can cause nuisance clutch engagement without a diode or relay.

Does the clutch engage?

The 4 speed fan uses 2 resistors and a relay combo to get 4 speeds. If the resistors operate w/o air flow their thermal sensor protector blows and doesn't reset.

The main 30 amp A/C circuit breaker resets automatically if it trips.

hotrodac

Thanks, Ice. Clutch does not engage. Looked at it and it stood still. I will have to check that condenser fan, like you said. Yes, its a Sanden 508. Yup, itas a BEHR. Yes again, condenser has a fan. BUT, there is only 3 speeds, not 4. Where are these resistors? Circuit breaker? I see a 20A (not 30) fuse on the driv side inside engine bay, right off the alternator junction box. No reset breaker. Arent those things only in houses?

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pippo on Mon November 15, 2010 8:00 PM

How might I have caused this "reverse polarity" by just un doing the console?? I did this many times before......

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NickD on Tue November 16, 2010 6:17 AM

Typically the blower switch in series with the mode switch is the source for 12 V to the compressor coil so the compressor does not engage unless the blower switch is on. The blower resistors are down stream from this connection, so with blown resistors, blower won't work but the compressor clutch still can. This 12V does not go directly to the clutch coil, has either a cycling switch or a thermal switch in series to disable the compressor if the pressures are not within limits of if the evaporator gets too cold.

Many times the act of just disconnecting and reconnecting a connector will not make good contact due to either a loose crimp or corrosion on the connector itself. Only takes a few microns of corrosion, sometimes barely visible to get a good connection. Find my myself continuously cleaning connectors to a bright metal finish and recrimping the female for a tighter fit. Most recently was on my radial arm saw, everything from the AC plug using corroded brass prongs, to starter switch relay contacts, to spade connectors, just cleaned or replaced all of it. Found a new neoprene line cord with plated plug prongs as opposed to bare brass, its working great now. Another fault is using unplated stranded wire that turns green, replaced all that wire with plated stranded wire and even soldered the spades. But what the heck, it worked for 45 years, just went to use it a couple of days ago, hit the switch and it was dead. But I haven't used it for a couple of months now. Arcing helps to make a good contact especially in high current circuits, but not if that corrosion builds up.

ice-n-tropics on Tue November 16, 2010 10:41 AM

3 speeds: Probably has a blower motor with windings tapped to provide 3 speeds instead of resistors. There were running changes. Same goes for the 20 amp protector. Never liked to do the same thing twice if it could be improved. Had bosses often tell me "It'll be OK, just leave it alone and don't worry about the quality, that's someone else's job, just let it ship out the door". The end result is all that matters in my book, not who you piss off.
Reverse polarity: welding on the car, brushing/wiping contacts against opposite charge point, negative voltage spike due to abnormal clutch disengagement (loose contacts etc.)
there should be a automatic reset breaker somewhere. I always used them. Explained and shown on page 102 of "How To Air Condition Your Hot Rod".
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Tue November 16, 2010 at 10:44 AM by ice-n-tropics

pippo on Tue November 16, 2010 7:02 PM

Quote
Originally posted by: ice-n-tropics
3 speeds: Probably has a blower motor with windings tapped to provide 3 speeds instead of resistors. There were running changes. Same goes for the 20 amp protector. Never liked to do the same thing twice if it could be improved. Had bosses often tell me "It'll be OK, just leave it alone and don't worry about the quality, that's someone else's job, just let it ship out the door". The end result is all that matters in my book, not who you piss off.

Reverse polarity: welding on the car, brushing/wiping contacts against opposite charge point, negative voltage spike due to abnormal clutch disengagement (loose contacts etc.)

there should be a automatic reset breaker somewhere. I always used them. Explained and shown on page 102 of "How To Air Condition Your Hot Rod".

hotrodac

Thanks, Nick, and Rod. So, this book, on page 102, is it on this site, maybe in Sticky" area or have to buy it? Reset breaker, hmmmm, this sounds like the first thing to do. Now, where is this reset? Any directions would be appreciated, of course. Under dash? In engine bay? behind glove box? Near ac on/off switch? Near fuse box?

Good thing its cooling off a tad. Still, its Florida!

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NickD on Wed November 17, 2010 9:49 AM

A schematic is a symbolic representation of the actual circuit, but that circuit does exist in the actual device. Particular in automotive, you may have a complete set of schematics, but they only show the I/O leads going into a box, don't show what's inside the box, but inside the box you can learn what it is doing by looking at the circuit. Repaired many an automotive box without the aid of a symbolic representation, but does help to have the so-called circuit diagrams in at least identifying the inputs and outputs. Its primarily a time saver.

One very useful part of having a manual is a component locater, you know that component you are looking for is somewhere within a space of 15 by 5 by 5 foot space, but where? But most of these drawings leave a lot to be desired, may show the component, but not where it is in relationship to the rest of the vehicle. Also love it when they say "solid state, do not test", that is incredibly stupid. Another one is always hot, really look for always hot stuff when you wake up to a dead battery.

While page 102 may say a circuit breaker, rare to find these devices in automotive, off the top of my head, only one I can think of was in a fast recovery circuit breaker used in older GM head lamp circuits. But that is long ago history, stockholders do not like the price of a circuit breaker when a user replaceable fuse can be used. I know we have to pay a small fortune of these, most of the cost is in that bubble pack, but fuse purchased in huge volumes were less than two cents each, recall around 1.23 cents per fuse.

Tapped field blower motor windings are also history as well as coiled field windings, much cheaper to use a permanent magnet where they are molded rather than being machined. But simply count the number of wires coming out of your blower motor, if more than two, namely ground and 12V, it is not a tapped field winding motor. Back in teh 60's and 70's, blower motors used a machined core with a field winding, motor case was screwed together and fully repairable with replaceable bushings and brushes, but a dealers list price was only six bucks. Today made like a throwaway tin can with a 250 buck pricetag, how things have changed. Just pay and bend over.

In older vehicles like yours, 90% of the problems can be found visually, never thought I would see the day when I am dragging out my four channel scope to find problems, yes, solid state boxes can be tested. Even with my own boys trying to teach them electrical troubleshooting, find myself saying, you call that clean, get down and give me 50. Hangover from my military days. But it works.

ice-n-tropics on Wed November 17, 2010 1:09 PM

Don't remember all component locations. Book on AMAZON.
Could write a book about those 2 wire field wound $10 motors. Mod ified 14000motors in my garage to add cooling vent holes and reverse direction for $2.5 each. Got a
few patents. Last one #5857839. Never got a "fare thee well"
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

pippo on Wed November 17, 2010 5:46 PM

oK....sounds like I wont be able to locate the breaker, ifn it is even there, huh? I will poke around, and review what you guys said here, if I can grasp it all, bit by bit.

Tanks

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pippo on Wed November 17, 2010 5:47 PM

Anyone know why this forum doesnt have an edit option?

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Dougflas on Wed November 17, 2010 6:42 PM

there is an edit. You have to select Login first

pippo on Thu November 18, 2010 9:34 PM

Quote
Originally posted by: Dougflas
there is an edit. You have to select Login first

Geez, thanks, Doug...I didnt know.

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pippo on Thu November 18, 2010 9:35 PM

Funny how one is allowed to post without loggig in...other forums dont allow that....oh well, no complaints!!

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NickD on Sat November 20, 2010 11:46 AM

Quote
Originally posted by: pippo
Funny how one is allowed to post without loggig in...other forums dont allow that....oh well, no complaints!!

Just to try out your statement, I logged out and tried to reply to this post, had to log in again before it would let me. Also had to lookup my password first, LOL. Log in is for most part, automatic, try logging out and posting or replying. Only my computer lets me log in automatically, if I am using another one far far away, have to log in manually.

ugmw177 on Mon November 22, 2010 2:44 PM

Hey OP,
I just completely overhauled an 88 spider a/c behr system. you have the switch control on the console and a thermostatic control attached to the back of the ductwork just to the left of the evaporator housing. Under the hood, there are two relays on the right hand inner fender and a 20amp power fuse on the left fender. the relays control the compressor and the condensor fan [condensor fan has two modes...on when a/c is on and on for cooldown if triggered by a heat sensitive probe in the fan shroud]

let me know if you need a schematic for the system.

pippo on Fri December 31, 2010 8:10 AM

Tanks, UGM. Sorry for delay, but weather has been too cold. Today Im gonna get back into it. I will see if the condenser fan works, guess I could apply 12v to it somehow. I do have the schematics , I have a shop manual. Thing is, sometimes its a challenge to understand.

Wish me luck........
Oh, it is a sander 507, not 508 (507 I understand has the ports on top, not onthe side). At this point, probably does nor matter, though.

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Edited: Fri December 31, 2010 at 8:11 AM by pippo

pippo on Fri December 31, 2010 3:29 PM

Yipeeeeee......it was a bad relay!!! I jumped the comp hot wire and it works!!!!!!

Happy new year!!!

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pippo on Sat January 01, 2011 5:28 PM

Uh, Ohhhh, celebrated too early....LOL I thought it was the relay, but auto zone tested it and its fine. Besides, they gave me a new one, and that too does not allow the compressor to kick on! Man, what could that mean? Just to be clear, I removed the relay and jumped the compressor main positive wire from the alternator junction box to the positive compressor wire, and that started the compressor and I got COLD ac!!

What is it guys? Oh, there is another relay next to the other one...I think its for the condenser fan when its too hot.....

Thnaks!

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mk378 on Sat January 01, 2011 10:49 PM

That means there's no power to the relay coil, you need to troubleshoot that side of the circuit to find out why. Not having a diagram of the car I can't say exactly, but in a car with basic manual controls, the circuit usually involves the fan switch (must be on a speed other than off), A/C button, evaporator temperature switch, and high / low pressure cutouts.

pippo on Sun January 02, 2011 8:53 AM

tanks, MK. Maybe I can scan the diagram and post. Let me see. At least we know the ac is actually still intact, mechanically. Whew.

May be dumb question, but is the relay coil iNSIDE the relay? There is power going from the main power wire from battery. Thats where I jumped it to the feed to the compressor......

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Edited: Sun January 02, 2011 at 8:55 AM by pippo

pippo on Sun January 02, 2011 11:04 AM

MK, here it is!! Man, that was tough....lol

anyway, hope this helps (you AND me). Thanks!

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mk378 on Sun January 02, 2011 3:32 PM

There's no compressor relay on that diagram. It appears that power for the compressor clutch comes directly from pin 2 of the control unit.

If there's a compressor relay in your car, it must be a different circuit than the diagram shows.

If your car has the same type of control unit, check that power (battery voltage to ground) is reaching pin 3 of the control unit with the fan on (key on and fan switch on). It appears the A/C system is powered up by the blue wire from the fan switch. With the fan switch on and the A/C control (#5) engaged, power should come out pin 2 of the control unit.

But again, that diagram may not be the right one for your car.


Edited: Sun January 02, 2011 at 3:34 PM by mk378

pippo on Mon January 03, 2011 7:44 PM

Thanks big time, MK. My fault- I didnt mean the comp had a relay, I guess. When I said it had a relay, I meant the blue comp power wire (blue) goes to a relay #15 on diagram (for sure), just like the diagram. This diagram is exactly like the setup on the car....no mods (only wierd thing as I penciled in the drawing, is the "M" or brown wire indicated as going to the switch "6" from fuse box is absent. 2 red wires instead....probably not a big issue.

OK, so to summarize, if I check for voltage at pin 2 of control unit, that should pretty much tell the story?


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Edited: Mon January 03, 2011 at 8:01 PM by pippo

mk378 on Tue January 04, 2011 5:47 AM

The control unit (#4) controls the compressor. Power for the control unit is delivered from the fan switch through the blue wire to terminal 3. Then if the driver has engaged the A/C control (#5) (is this just a simple on/off switch?) and the evaporator thermostat (#2) is OK (not too cold), the control unit sends power out terminal 2 which goes to the compressor.

Relay #15 is wired to turn the condenser fan on whenever the compressor is on. What you did with a jumper was to cross the circuits to start the compressor using power from the fan fuse (#16) instead of the normal path through the control unit. That is not how the relay normally works.

Interesting the system shows no over / under pressure switch. Guess in the old days of cheap R-12 you'd just cross your fingers. A good practice with many things on an Italian car.

Edited: Tue January 04, 2011 at 5:51 AM by mk378