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Wiring past alarm on '89 951?

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Wiring past alarm on '89 951?

Post  docwyte on Sat Apr 04, 2015 10:39 am

So how do you do this? I stupidly removed the alarm ECU on my car without realizing power for several necessary things (like the alternator charge wire) go through that circuit.

I can't follow the Clark's Garage bypass instructions because I don't have the alarm ecu in place at all anymore.

So, how do you just completely wire past it, with the alarm ECU gone?

Push comes to shove I have another alarm ecu on its way to me, but I'd like to get this done asap...


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Re: Wiring past alarm on '89 951?

Post  docwyte on Sun Apr 05, 2015 4:24 pm

OK, turns out the bypass described on Clarks Garage is ONLY for the EARLY cars, not a late 88+ car like my 89.

I've read on the web that I should jumper 1 to 3 instead of 1 to 4. Can anyone confirm that they've done that and its worked?


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Re: Wiring past alarm on '89 951?

Post  docwyte on Sun Apr 19, 2015 5:30 pm

OK, here's a little Alarm ECU 101. There are actually three different alarm ECU's that Porsche used. The early cars got 911.637.104.00, the Clark's Garage bypass procedure works for cars with this ECU. Then the "Middle" cars ('87-'88?) cars got 911.637.104.02. Both of these plugs on the cars body side are white. Sometime in 1989 Porsche switched to the "Late" Alarm, which has a blue plug and the part # starts with 928.

My car is a 1989, but didn't have the blue body plug and the 928 part # alarm ECU didn't plug into my car. The Clarks Garage bypass procedure DOES NOT work on the Late cars! It should work on the "Early" and "Middle" cars but check the wiring colors against what my car had and what Clarks Garage says they should be. If they match Clark's Garage, use it, if not, use my procedure.

Additionally you need to match the 911 part # alarm ECU with a 944 part # alarm relay, while the 928 Alarm ECU gets a 928 Alarm relay part #.

Ok, here's where Porsche started F'ing with me again. So even though my car is an 1989 and had the white plug Alarm ECU harness, it STILL didn't have wiring to match the 1987-1988 cars like the Part # 911 Alarm ECU has.

So that meant that even though the Alarm ECU plugged in, it still wasn't working. I couldn't open my rear hatch with the key and the alarm and relay were clicking away madly.

Sigh. Time to do some more research on how to properly bypass the alarm in the 1989's. A little while later I had a procedure that was supposed to work. Guess I'll either burn up my wiring harness or it'll finally work!

So I went out and did it and it WORKED! Holy crap. I can finally open my rear hatch with the key from the outside!

Ok, so what did I do?

Well, first off you need to make two jumper wires with male spade connectors on each end. Now go unplug the alarm ECU. There are two plugs, one large 8 wire one, one small two wire one. On the large 8 wire plug, jump the black with red stripe wire to the green wire, which should be jumping pins #1 to #3.

Now go to the fusebox and find relay G19, which is the alarm bridge relay and remove it. You need to jump pins 4 to 5 in it. According to what I read, this was the red wire to the red/black wire, but on my car it was the red wire to the red/blue wire.

You're done! Dance a jig now that you've FINALLY gotten rid of the damn OEM alarm!


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