Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Mar 2011
Location: Shreveport LA
Posts: 75
Garage
A/C only works on accessory

Hi everyone, need some help. All of sudden, my a.c. only works in my 83 911 sc when the key is turned to accessory. When I start the car, the a.c. stops completely. Turn off the engine, put the key in accessory, and it works again. Diagram shows that the ground wire (yellow) for the smugglers box relay goes to the starter!? Can anyone explain the reason for that to me, please? Problem seems to be that yellow ground wire, as when I ground the wire out, a.c. works fine. Does the starter provide a ground when the engine is running? I don't remember the a.c. working on accessory before. Thanks!
Old 11-09-2018, 11:13 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
T77911S's Avatar
 
Join Date: Oct 2006
Location: MYR S.C.
Posts: 10,842
have not looked at diagram but yes, the starter could provide the ground,. it does this so that when you start the car the AC cuts off.
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 11-09-2018, 11:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Mar 2011
Location: Shreveport LA
Posts: 75
Garage
I get that, but why would it stay off when the engine is running...
Old 11-09-2018, 01:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Apr 2008
Location: Houston TX
Posts: 7,042
The yellow wire is not the relay ground. It's designed to shut down the A/C compressor when you are cranking the engine. Key to start, powers starter solenoid, puts +12V to the yellow wire, which puts +12V to pin 86 of the relay. If you have the A/C switch on, then you also have +12V to pin 85 of the relay. +12V on both sides of the coil=no current, so the relay shuts off. It's part of Porsche's special little way of triggering some relays backwards...

To test that system, the yellow wire at the relay should only be hot when the key is to "START".
__________________
Mike Bradshaw

1980 911SC sunroof coupe, silver/black: The Wurster
2006 Mazda3 5 door, M-speed exhaust: The Ricer
Putting the sick back into sycophant!
Old 11-09-2018, 01:10 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Been here a while
 
Join Date: Apr 2004
Location: East coast, west coast, typ. 35,000 ft
Posts: 1,311
I'll tell you a little story, it may or may not apply to this, but it sounds similar to me.

I recently got the AC working on my 72 hotrod, Blucille.

I was in the middle of a 1300 mile rally in distant parts. Suddenly, when I got out of the car, I noticed the AC blower would stay on, with the key off and removed. The cig lighter would stay on too. I found this behavior very odd, checked the relay in the smuggler's box, all was ok. The shop that has helped me in the past theorized the electrical portion of the ignition switch....I doubted that since not ALL the accessories were staying on.

So, after the rally I dug in. I found the one wire that provided power to the AC blower was tied to the cig lighter at the fuse box. The wire had been chafing on the backside of the fuse box, to fuse #1, which was constantly powered. So, when the ignition switch would turn off, the power from fuse 1 would still be available to that circuit. I insulated the wire, rerouted it, and the problem was completely solved.

In other words, if this is a new problem, start with the pieces that were recently touched, and then look at common failure points, like the fuse box.
__________________
Found a period correct hotrod motor, but still looking for 1972 911t motor, 6121622
Old 11-09-2018, 02:02 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Join Date: Mar 2011
Location: Shreveport LA
Posts: 75
Garage
Ok, after a good 8 hours work....power comes in on the black. Doesn't work at all with yellow disconnected.....works with "yellow" pin grounded. So, left the yellow wire off, grounded the pin, and A/C works fine. Thanks everyone for the ideas. Its going to be that way for the time being.
Old 11-09-2018, 03:13 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 04:39 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.