Automotive Air Conditioning Information Forum (Archives)

pippo on Fri June 21, 2013 4:56 PM

People,

Still having trouible. 87 sunbird GT non turbo. The buss fuse near the temp control box under dash has blown 2X. Of course, this supplies voltage to the compressor. Where should I start to find the cause of this? Ever have such a thing happen? What are likely to be the causes?

Thaks

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wptski on Fri June 21, 2013 6:40 PM

Does it blow as soon as the clutch is energized? I have a diagram for a '78 GM product which shows the clutch to measure 3.65 ohms at 80F. You'd need a fairly good meter to read correctly that low and if it reads lower than that, it'll blow a fuse. Resistance increases with temperature increases. Using any kind of meter, scratch the paint good and read from either/both contacts on the coil to the metal housing. It should be open or no contact.

pippo on Fri June 21, 2013 7:00 PM

Thanks, wp. Not sure if your 78 diagram would apply to my 87. No, it does not blow right away, as I drove to work for at least 20 minutes one way and no blown fuse during the trip. Im thinking maybe its in the dash mounted control levers(?). The rectangular switch inside the manual control lever has a connector that has a slight burnt plastic insulation- not sure that would be the culprit.

Remember- aftermarket system (with factory compressor). Any idea? If you still think its relevant, I will try to get a reading on my clutch, although, man, its soooo tight down there......

Thanks, buddy

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Edited: Fri June 21, 2013 at 7:02 PM by pippo

pippo on Fri June 21, 2013 7:36 PM

Just went in the car and looked at that switch- if it helps, it is brown rectangular , with a pin connector on one end that says "com". Burnt part of that terminal. Also, theswitch says "CHERRY". E-14. I can tell you, now that I think of it, for years, I had to force the control lever/tab very hard , kinda to drive the lever into the switch, which has a curved spring like contact "blade". That blade pushed down onto what is probably contact "pin". I had to force that lever hard and not move it back if I wanted the ac to go on easily. Otherwise, no problems. Maybe its giving out now??

Maybe Im chasing th wrong thing, I dunno......

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wptski on Fri June 21, 2013 7:38 PM

Quote
Originally posted by: pippo
Thanks, wp. Not sure if your 78 diagram would apply to my 87. No, it does not blow right away, as I drove to work for at least 20 minutes one way and no blown fuse during the trip. Im thinking maybe its in the dash mounted control levers(?). The rectangular switch inside the manual control lever has a connector that has a slight burnt plastic insulation- not sure that would be the culprit.



Remember- aftermarket system (with factory compressor). Any idea? If you still think its relevant, I will try to get a reading on my clutch, although, man, its soooo tight down there......



Thanks, buddy
Burnt plastic isn't a good sign. In the motor world they have what's called a rolling short which can happen under load. Everything will check good while not running. Winding like in your clutch coil can also be check under a stress with a meggar which can put voltages up to 5KV or down to 50V with some models. Coil may pass a meggar test and still have a rolling short. Rolling short detection is rocket science.

I know they don't design stuff for easy access! I use to maintain 17 machines that had four coils, two were clutches and two were used as a brake. Depending on the physical mounting, it can either be a clutch or brake. I've seen 1/8" grooves in the plates(armature), some on bent shafts and run with no problem.

It's all up to you what to do.

EDIT:
Maybe your on to something.



Edited: Fri June 21, 2013 at 7:39 PM by wptski

pippo on Sat June 22, 2013 7:31 AM

Thanks, man!

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WyrTwister on Sat June 22, 2013 6:34 PM

The 2 1990's GM cars we have , use a relay to energize the clutch . Does yours ?

If so try unplugging the relay & looking for something burned .

Drive the car & see if the fuse still blows ? If not , replace the relay and unplug the cable & connector from the compressor clutch . Again , test drive ?

Look for a bare spot on the wiring where the wire has rubbed on something & exposed the wire , through the insulation .

God bless
Wyr

pippo on Sun June 23, 2013 1:53 PM

Quote
Originally posted by: WyrTwister
The 2 1990's GM cars we have , use a relay to energize the clutch . Does yours ?



If so try unplugging the relay & looking for something burned .



Drive the car & see if the fuse still blows ? If not , replace the relay and unplug the cable & connector from the compressor clutch . Again , test drive ?



Look for a bare spot on the wiring where the wire has rubbed on something & exposed the wire , through the insulation .



God bless

Wyr

Yup, there is a relay to energize clutch, but remember- its aftermarket, if it matters. I looked and no burn spots visible on relay. Still, I will try your suggestion- good tip. I will advise monday what happens.....



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pippo on Sun June 23, 2013 2:46 PM

http://www.autoacforum.com/forumimages/IMAG0074.jpg

heres a picture of the relay! (above url). I pulled it off and theres oxidation build up inside it. Not sure how yukky this is- I never opened up a relay before, but the crusty junk isnt a good sign to me. What do yous think?

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pippo on Sun June 23, 2013 2:47 PM

Man, cant get the picture uploaded on this site. What am I doing wrong....... Well, guess yous can copy the link and enter in the bar of a new page and view. Try this: http://www.autoacforum.com/forumimages/IMAG0074.jpg

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Edited: Sun June 23, 2013 at 2:49 PM by pippo

wptski on Sun June 23, 2013 3:07 PM

Looks bad but does it still work? You can check it using the car battery and a meter or test light. I've used a DeWalt 14.4V in the past.

Edited: Sun June 23, 2013 at 3:08 PM by wptski

pippo on Sun June 23, 2013 4:05 PM

Hmmmm, guess I could try to check the relay, but isnt this whole idea to isolate the culprit to get a NEW relay then test the car's ac out during a drive? I mean, even if the bad relay "tests out", it could still be bad under load, right? Then why should I gamble again with this ugly relay? Maybe Im not getting your idea, wp. You see, this ugly relay worked, for a while or so, as long as I had a new fuse installed. But it didnt last for long. Get what Im saying? Feedback appreciated.

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Edited: Sun June 23, 2013 at 4:06 PM by pippo

pippo on Sun June 23, 2013 5:34 PM

Clutch resistivity is 4.9 ohms.

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pippo on Sun June 23, 2013 7:22 PM

OK, battery neg and pos terminals at Relay contacts 86 and 87, and I hear a clicking, voltmeter terminals at 30 and 87, and I get 0.4 ohms. Also, same result on a brand new relay, so guess relay is still good (?). Why though, just curious, when I take a VOLTAGE reading on same relay terminals I get no voltage (old and new relay)?? Aint I supposed to get a V reading?

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wptski on Sun June 23, 2013 8:12 PM

Quote
Originally posted by: pippo
OK, battery neg and pos terminals at Relay contacts 86 and 87, and I hear a clicking, voltmeter terminals at 30 and 87, and I get 0.4 ohms. Also, same result on a brand new relay, so guess relay is still good (?). Why though, just curious, when I take a VOLTAGE reading on same relay terminals I get no voltage (old and new relay)?? Aint I supposed to get a V reading?
You get no voltage when and on what terminals? From what you stated, 86/87, one is grounded and the other receives 12V to open/close relay contacts from your AC switch or lever. That means that 30/87, one goes to the clutch coil and other should have 12V supplied probably when vehicles is running only. When contacts are closed, you have 12V going to your clutch coil.

Were you expecting to see 12V on 30/87 on your bench test? You won't.

It's possible that the relay might not be working correctly all the time. The only way to prove that is monitoring voltage while you drive. I've monitored a EGR problem with a vacuum gauge, DMM and a scope all while driving a manual shift by myself!

mk378 on Sun June 23, 2013 9:36 PM

The most common reason for car fuses to blow is frayed wiring that lets the live copper touch grounded metal. This is especially true on aftermarket work. Inspect all the wiring thoroughly. Relays practically never fail in a way that makes them alone blow fuses.

pippo on Mon June 24, 2013 7:31 AM

I think I get it now, WP and MK. Thanks as always for explaining!

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pippo on Tue June 25, 2013 7:03 PM

Dang, this is what Im needing, and have to buy 800 of them!!

http://www.mouser.com/ProductDetail/Cherry-Electrical/E14-00H/?qs=%2fha2pyFadugwji3neNyMejuPT9UdgJuTaXZFiebqt1U%3d

snap action switches, Cherry Co. Anyone here know where I can buy 1 or 2? Cant even get them on ebay.
Thanks

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wptski on Tue June 25, 2013 10:46 PM

You found a bad switch? Got a picture?

mk378 on Tue June 25, 2013 11:26 PM

It's called a micro switch. They have been the same since the 1930's, and since the patent has run out long ago, many companies besides Cherry make an identical unit. The original company was of course "Micro Switch Inc."

pippo on Wed June 26, 2013 7:57 AM

Thanks, MK. WP, just take that link I posted and open new window, then click it into the bar on top and you will see the switch. I struggled to get the pic on this site with no luck. So, One company sells them but I need to buy 800!!! Where can I buy one/two, people? Oh, I checked resistivity and I got 0.7 or so. Is the switch still good, and maybe its the spade connectors (which are a tad burnt)?

I could try to replace the connectors then try the old switch again, and see if the fuse holds, right?

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wptski on Wed June 26, 2013 10:19 AM

Quote
Originally posted by: pippo
Thanks, MK. WP, just take that link I posted and open new window, then click it into the bar on top and you will see the switch. I struggled to get the pic on this site with no luck. So, One company sells them but I need to buy 800!!! Where can I buy one/two, people? Oh, I checked resistivity and I got 0.7 or so. Is the switch still good, and maybe its the spade connectors (which are a tad burnt)?



I could try to replace the connectors then try the old switch again, and see if the fuse holds, right?
Ever hear of a "voltage drop test"? It's a voltage drop under a load. Lots of times it's done on car battery cables. They have special testers that apply voltage under high amperage then measure the resistance of contacts. You can do this by simply measuring voltage across the switch while it's operating. In theory it should read zero but if it reads, say a few volts that means it's dropping that inside the switch which causes heat. I've seen this on a basement dehumidifier compressor, spot welded pigtail wire on a overload where that spot welded contact got to 316F(seen with a infrared imager) and melted wires together. No fire but this caused the unit to cycle ON/OFF every few minutes.

There is also this gadget: TESlite which I have but never used for its intended purpose yet.

Edited: Wed June 26, 2013 at 10:52 AM by wptski

A/C-DC on Wed June 26, 2013 2:44 PM

Quote
Originally posted by: wptski
Quote

Originally posted by: pippo

Thanks, MK. WP, just take that link I posted and open new window, then click it into the bar on top and you will see the switch. I struggled to get the pic on this site with no luck. So, One company sells them but I need to buy 800!!! Where can I buy one/two, people? Oh, I checked resistivity and I got 0.7 or so. Is the switch still good, and maybe its the spade connectors (which are a tad burnt)?


I could try to replace the connectors then try the old switch again, and see if the fuse holds, right?

Ever hear of a "voltage drop test"? It's a voltage drop under a load. Lots of times it's done on car battery cables. They have special testers that apply voltage under high amperage then measure the resistance of contacts. You can do this by simply measuring voltage across the switch while it's operating. In theory it should read zero but if it reads, say a few volts that means it's dropping that inside the switch which causes heat. I've seen this on a basement dehumidifier compressor, spot welded pigtail wire on a overload where that spot welded contact got to 316F(seen with a infrared imager) and melted wires together. No fire but this caused the unit to cycle ON/OFF every few minutes.



There is also this gadget: TESlite which I have but never used for its intended purpose yet.

A/C-DC on Wed June 26, 2013 2:47 PM

Try this site for your switch. $6.47 + shipping. Buy a couple of them!

Cherry switch

pippo on Wed June 26, 2013 4:47 PM

Good hit, ac/dc! Howd you find that supplier??!! Man, I like this site! Also, I might try this voltage drop test- while Im waiting for the switch to arrive, once I order it. Heck- you know, even if I buy a new switch, may be the fault of the wires. Gotta cover all the scenarios.

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