Need gurus for 83sc

damian911 · 06-29-2011, 10:59 AM

hello there, wondering if someone can help me diagnose an electrical problem with my 83sc 911 a/c compressor not firing up...I recently did almost an entire redo of the air condition replacing the hoses and evap and front condensor. I then vacuumed the system and replaced the oil and when i was ready to put the freon the compressor wouldnt turn on. The wire has no juice nor does the front condensor blower turn on but he evaportor motor does blow ...I just replaced the evaportor blower relay in the box thinkn it may be alittle burned and the new relay did not change anything.....I need help ....damian

jdbunda · jdbunda's Garage

Do you have the Bentley manual? I'm trying to remember where I saw that AC troubleshooting chart...

damian911 · 06-29-2011, 03:21 PM

Yes i do have one....let me know ive looked at it but didnt find anything like that....thks

porsche930dude · porsche930dude's Garage

It probrobly has a low pessure switch. You need the pressure in the system for it to turn on. Or you can jump the switch

damian911 · 06-29-2011, 05:07 PM

I dont believe i ever seen a pressure switch anywhere on the system exspecially on a hose next to the compressor ....

damian911 · 06-29-2011, 05:09 PM

i have no 12v going to the compressor wire for it to engange ....but it does have two cans of freon that i put in, hopefully it is still holding....

Bob Kontak · Bob Kontak's Garage

Isn't there some kind of resistor thing in the foot well of the passenger side? Hooked into the wooden floorboard.

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_AC.jpg

There is a temp switch. Feeds the fan and condensor cooling fan. Bet that is it. Where is it?

Edit - the temp switch is the temp dial next to the fan knob by the shifter. Just read a post where the temp switch (dial) wires were touching.

damian911 · 06-29-2011, 09:46 PM

My switch i believe seems to be working if i turn it to position 1 2 or 3 the evap motor runs accordingly but the compressor clutch doesnt turn on nor the front condensor blower..... Can anyone explain how the thermal switch works down below at the footwell, i saw it and doesnt look like much????

damian911 · 06-29-2011, 09:49 PM

thinkn about running a 12v power straight to the compressor tomorw and see what i get...and im going to look at the wires between the temperture and fan switch...thks

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by damian911

My switch i believe seems to be working

Edit - After writing up the below I see that you are going to check the temp switch. Doh!

The link above shows the fan switch as the main control unit. The temperature switch is BETWEEN the fan switch and the compressor clutch. The temperature switch is also between the fan switch and the relay which feeds the condenser cooling fan motor.

If the temp switch (or associated wiring) is bad neither the clutch or the condenser cooling blower will run.

If the fan switch is screwed up inside and does not send juice to the temp switch then that could cause the same problem.

Temp switch is to the left of the fan switch in the pic

The evap resistor in the footwell feeds the evap fan. I would chill on that since you are getting action there.

See post #10 for a sort-of explanation on the evaporator resistor in the footwell.

My AC is....too cold!!!!!!

If you run a straight line to the compressor the clutch will work. - Betcha!

damian911 · 06-30-2011, 09:22 AM

yea i hooked it direct and the clutch enganged .....but i didnt get the readings i was looking for at the gauges.....haa -5 on low and 150 on high if that makes any sense.....wow bad

damian911 · 06-30-2011, 09:31 AM

i was also messing with the end of the temperature wire which inserts into the evap and it broke...i then was able to pull it out, the broken end outta the box, the end w the copper end and reinserted the wire into the box temporarily...guess all the moving and it being almost 30yrs old it had enough......could this be the entire problem? or should it still work??

Barrpete · 06-30-2011, 10:31 AM

Quote:

Originally Posted by damian911

i was also messing with the end of the temperature wire which inserts into the evap and it broke...i then was able to pull it out, the broken end outta the box, the end w the copper end and reinserted the wire into the box temporarily...guess all the moving and it being almost 30yrs old it had enough......could this be the entire problem? or should it still work??

That is actually a capillary tube filled with an inert gas, not a wire. If you broke it your temp switch is toast and you need a new one.

The way it works is that inside the switch is a bellows connected to that tube that opens/closes a set of contacts that turns the compressor on/off as the evaporator temp changes.

Bob Kontak · Bob Kontak's Garage

Barrpete - Excellent info. Damian911 - keep us posted as to the resolution.

damian911 · 06-30-2011, 11:25 AM

wholly crap!!!! Im hoping and thinkn this is may be the reason i have the problem im having!!! ??????

Barrpete · 06-30-2011, 02:09 PM

An easy test is to bypass the temp switch. Just jumper the 2 leads to the switch together. If the compressor clutch kicks in that was your problem. You can run your AC with that switch bypassed but the compressor will run continuously and you run the risk of icing up the evaporator after a while.

damian911 · 06-30-2011, 05:17 PM

Barrpete, thks for that info i just had a friend tell me about it just recently, do u know the color of the 2 lead wires for a 83sc???

Bob Kontak · Bob Kontak's Garage

Green and white into the temp switch from the fan switch and green out of the temp switch to the relay. There is a terminal downstream from the temp switch that splits off to the compressor and that wire is black. You can see it all in the link in post #7

The SC's are pretty much the same.

Barrpete · 07-01-2011, 07:02 AM

Quote:

Originally Posted by bob kontak

green and white into the temp switch from the fan switch and green out of the temp switch to the relay. There is a terminal downstream from the temp switch that splits off to the compressor and that wire is black. You can see it all in the link in post #7

the sc's are pretty much the same.

+1

damian911 · 07-16-2011, 03:09 PM

Awesome thread everyone!!!! Wondering if u can help me finish it off its been about 2 weeks since i removed the wires and now a little confused, where do the wires reattach to the back of the temperature switch?? Its also confusing with the new switch because the numbers in the back of the new switch are different from the numbers in the back of the old oem switch?? can anyone advise??? Thanks.....Damian