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New cooling fan relay energizing A/C fresh air blower relay with no key in ignition?
I've decided to make a new thread as I've encountered an entirely new issue since making this forum post (https://rennlist.com/forums/924-931-...ng-on-off.html) hoping to get more eyes on this thread to try and narrow down the issue.
So I've got this weird issue that I can't seem to figure out. Long story short my A/C wasn't working and I found the original A/C relay behind the glove box had failed, so I ordered a new OEM replacement from Porsche. Relay arrived and I figured I'd swap the cooling fan relay and A/C relays around.
I placed the original working relay from the relay block position #1 to the A/C relay spot behind the glove box and inserted the brand new relay into position #1 of the fuse block. As soon as I went to insert the new relay, I heard the A/C air blower relay (position 3 on the fuse block) click and energize. Blower motor started running at its position "0" setting (as if ignition was on) and I could turn the A/C on without they key in the ignition. I was unable to get the radiator fans to stop running (since the A/C was turned on) unless I removed the cooling fan relay completely. Turning the A/C switch back to "0" had no effect.
I swapped both relays (brand new relay into the A/C relay position and original working relay back into its original cooling fan relay position on the fuse block). Upon inserting the original relay, I did not hear the A/C air blower relay click or energize, the blower fan no longer runs and I cannot turn the A/C on without the key in the ignition.
I figured maybe my new relay was defective (I tested the relay and found the diode was bad) so I had a new one ordered. Relay arrived and I again inserted the relay into position 1 on the relay block. As soon as I made contact with the board, the A/C air blower relay (again position 3 on the relay block) clicked and energized. Maybe I didn't properly test the diode in the original relay, but regardless the same issue still persists with the new relay.
I cannot figure out why the brand new relay is causing the relay to energize and allow the blower motor and A/C to work without the key in the ignition, where the original relay isn't having these issues. Any suggestions!?
In your other thread I mentioned to test the ignition switch. I would go ahead and do that just to eliminate as a possible cause.
Whenever things on the car turn on without the key in the ignition, I feel like its worth a shot to check and/or replace. They also seem to be intermittent when they start to go bad so it might be causing some confusion with the original relay "working". https://www.clarks-garage.com/shop-manual/elect-17.htm
Last edited by walfreyydo; 08-28-2023 at 03:18 PM.
In your other thread I mentioned to test the ignition switch. I would go ahead and do that just to eliminate as a possible cause.
Whenever things on the car turn on without the key in the ignition, I feel like its worth a shot to check and/or replace. They also seem to be intermittent when they start to go bad. https://www.clarks-garage.com/shop-manual/elect-17.htm
I'm definitely going to check that, I'm at work currently. In my mind if the ignition switch as going faulty, you'd think I'd be able to power anything (power windows, power mirrors, etc). Such as weird issue but our cars are approaching the 40 year old mark lol!
Your new relay in position #1 is either the wrong relay type, or it's internal diode is shorted.
I originally thought the internal diode was shorted and "thought" I had tested the diode with my multimeter correctly so I had Porsche order me a new relay. New relay was still causing the same symptoms. I verified the new relay to my working original relay via on relay schematic and pins all seemed to match. I'll double check again. Thanks for the reply.
Your new relay in position #1 is either the wrong relay type, or it's internal diode is shorted.
^^ what this guy said. Also verify the relay part numbers are accurate based on what you can find on FCP/Auto Atlanta or other parts sites for the oem relay for your year. For some reason Porsche took down the 944 PET Parts Catalog PDF's (huge huge bummer) otherwise I would direct you there. You might have the wrong relay?
^^ what this guy said. Also verify the relay part numbers are accurate based on what you can find on FCP/Auto Atlanta or other parts sites for the oem relay for your year. For some reason Porsche took down the 944 PET Parts Catalog PDF's (huge huge bummer) otherwise I would direct you there. You might have the wrong relay?
I have the 1982-1985 PET's stored on my computer. Part numbers from the PET:
They looked correct, also I took a picture of all the relays side by side the first time I went to replace the failed relay:
Part numbers matched on all the relays as side from the last two digits which I'm pretty sure are revision numbers. I'll double check the schematic on the relays of .03 to the .01 relay to make sure everything is where its supposed to be. Again, just weird to me how .01 works just fine (can't turn blower motor on or use A/C with no key/ ignition off) but .03 causes the fresh air blower relay to energize with no key in the ignition/ no power... .
EDIT: I know on my 84 944 the same relay is used for both the cooling fan relay and the A/C relay. I thought at first maybe for instance the cooling fan relay was different but that isn't the case as both were the same part numbers upon removal.
Last edited by ALEXTHEGREAT; 08-28-2023 at 06:18 PM.
Alright I got home and had a chance to test both relays. Results below,
NEW .03 relay positive lead on pin 85
NEW .03 relay positive lead on pin 86
OLD WORKING .01 relay positive lead on pin 86
OLD WORKING .01 relay positive lead on pin 85
So looks to me like my second new relay has a shorted diode? Since both directions have the same voltage drop (voltages were constantly fluctuating both ways, anywhere from 0.1V - 0.01). Whereas my .01 relay shows .5v voltage drop one direction and "OL" reading the other direction.
Last edited by ALEXTHEGREAT; 08-28-2023 at 09:59 PM.
EDIT: I know on my 84 944 the same relay is used for both the cooling fan relay and the A/C relay.
Do not think the cooling fan relay [141 951 253B] at #1 position in fuse/relay panel and the a/c relay [944 615 113 01] at #3 position in fuse/relay panel are the same part on an '84 944.
Do not think the cooling fan relay [141 951 253B] at #1 position in fuse/relay panel and the a/c relay [944 615 113 01] at #3 position in fuse/relay panel are the same part on an '84 944.
They are not. There is quite a bit of confusion around these relays as the schematic, workshop manual, and owner's manual all disagree on their naming. I prefer to use the schematic naming, which has "Air Conditioner Relay" in the right side of the car, the "Cooling Fan Relay" in position 1, and the "Fresh Air Blower" relay in position 3. I've marked the positions on one copy of the schematic.
08-28-2023, 01:49 PM
New cooling fan relay energizing A/C fresh air blower relay with no key in ignition?
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