Clarify alarm module bypass on SC?

[tirwin]

Sorry if this has been asked an answered but I couldn't seem to find a conclusive answer. Most of the posts referencing alarm bypass are for 84-89 Carreras with DME. Trying to find something specific to SC and the posts I've found don't have much follow-up.

In this picture below, I understand the need for the jumper across pins 61 & 61 to complete the charging circuit.

My first question is this -- on an SC, is the 2nd jumper across 30 & 15 needed? Is the alarm module just a relay? Is it an active component that needs power itself? I know it prevents the car from starting by putting a ground on pin 85 of the FP relay. What’s the purpose of pins 15 and 30? 30 is to provide power to the horn?

Second question is if I leave the door & trunk contact circuits disconnected here, will it interfere with normal function? I don't think so, but wanted to confirm. They normally get power from fuse #18 circuit. It appears the alarm wiring is a separate circuit path used to trip the alarm if the doors or trunk are opened when the alarm is activated.

[tirwin]

Well the car starts WITH jumper 1 and WITHOUT jumper 2.

[86 911 Targa]

"No Cut" method for bypassing factory alarm



^^^^^
Let's see if this helps.

Best,

Gerry

[tirwin]

Gerry,

Thanks for posting that. I think that’s specific to the ‘84-‘89 Carreras with DME?

Since the SC’s don’t have a DME, I don’t believe there is an analogous jumper required so would like to confirm.

In the diagram I posted, there is a constant hot (pin 30) that comes from the battery. The alarm would need that to provide power to the horn. That makes sense. I don’t understand why there is a switched power from the ignition switch (pin 15). I can’t decipher the purpose.

Also, I thought in other posts that pins 61 and 61 need to be jumped to complete the circuit from the alternator to charging light? I thought the charging light is required for the battery to charge. I don’t really understand what this is part of the alarm. I guess the theory is that if the alarm is activated it prevents the battery from charging. So I think this needs to be there. When I start the car with 61/61 jumped the charging light is on and with the key in ON position and goes out once the car is started as it should. Now that I think about it, I did not try starting the car with 61/61 jumpered.

It’s a PITA to get to the alarm module so I’d appreciate it if anyone can confirm that only jumping 61/61 is required on an SC before I put all the fresh air blower crap back in place. Really don’t want to have to do it again anytime soon!

[tirwin]

Here’s a picture of my alarm module. Slightly different pin numbering.

[tirwin]

One more thing... Gerry, in that thread you provided — there is a post in there that confused me. It says jumping 15 to 87a is not needed in an SC. I was confused because there is no pin 87a in the alarm module on an SC!

I just don’t get the logic for what pin 15 is used for in the SC version. The wiring diagram shows pin 15 only provides 12v when the ignition switch is in START or RUN. It seems the alarm module needs power all the time.

In the Carrera version it looks like pin 15 is providing power to the DME relay, which I think, has to do with running the FP. I don’t have experience with the Motronic cars so not 100% sure this is correct. If that is correct I see the rationale for needing that jumper.

The key difference seems to be that in the DME cars, the alarm module provides power to the DME relay. No power to DME, no start. In the SCs, the alarm modules disables the FP by putting a ground to pin 85 on the FP relay. Ground present on pin 85 of FP relay, car will start but not run as relay is picked.

I did a continuity test from the wire that connects to pin 85 (isolated) and pin K1 on the alarm module side and they are directly connected.

[86 911 Targa]

Your alarm module is a -00.

For the m/y '86 it is a -02.

pm me please.

Gerry

[tirwin]

Gerry and I spoke.

My belief is that the -00 and -02 alarm modules are not compatible.

In the -02 module, the jumper is necessary between pins 15 and 87a. In European DIN wiring, 15 means switched power from ignition switch, 87a means normally closed contact and 86 means coil +. So if the alarm is tripped, there is no power to the coil via the DME.

This is very different from the -00 module which interrupts the fuel pump by providing a ground to pin 85 on the FP relay via pin K1 on the alarm relay.

I have no idea what pin 15 on the -00 alarm module is for but it is apparently not needed to bypass the alarm module.

Surprised this hasn’t been discussed before...

[timmy2]

Maybe no discussion as most have completely removed the alarm wiring when dealing with them?
Pretty much everything can be unplugged related to the early alarms to remove.

[tirwin]

Originally Posted by timmy2

Maybe no discussion as most have completely removed the alarm wiring when dealing with them?
Pretty much everything can be unplugged related to the early alarms to remove.

I was waiting for you to jump in.

Ok, so is the jumper from 61 to 61 needed? If I look at the wiring diagram that shows the alternator to charging light in the gauge, it shows that is a blue wire. No mention of the alarm circuit.

If I look at the alarm wiring diagram I posted it shows that it is a blue wire between the alarm module and the alternator and and blue/red wire between the alarm and the battery charge indicator light.

So is this 61/61 jumper needed at all? Any theories as to the purpose of this circuit? I assumed the intent was to break the circuit and prevent the battery from charging if the car was stolen.

I can remove the jumper and test if the light goes out after starting but I won't be able to get back to it until next weekend.

[rattlsnak]

Tim, are you sure you have the fuel pump relay wiring figured out? usually, the alarm module provides the ground to the fuel pump relay and if it triggered it takes it away. That's what controls
the relay.

[tirwin]

Originally Posted by rattlsnak

Tim, are you sure you have the fuel pump relay wiring figured out? usually, the alarm module provides the ground to the fuel pump relay and if it triggered it takes it away. That's what controls
the relay.

Yes. 87a/30 is a normally closed contact that provides power to the fuel pump when the ignition switch is in START or RUN.

See this post: Fuel Pump Relay Woes...

When ground is present on pin 85, it trips the FP relay. It switches power to from 87a/30 to 87/30 if memory serves, which has no power in START or RUN. There are 3 things that can put a ground on pin 85: alarm, air pressure plate switch that is part of the CIS and rev limiter.

For further proof, the alarm module is currently unplugged and I have a jumper between both pins 61 on the harness wire. The car starts are runs fine with no ground on pin 85. We did this test what seemed like 100 times that day looking for the wire that was the source of the ground. I labelled it when I found it and did a continuity test to pin K1 of the alarm module harness plug to verify.

The -02 module (later Carreras? not sure what year it started) wiring shows that it provides power to the coil+ of the DME relay. I am basing this on DIN 72552 pin definitions (https://en.m.wikipedia.org/wiki/DIN_72552).

[rattlsnak]

Thats right, i was think DME setup as well. Then yes, just disconnecting the alarm module connector and jumping the the two Alt pins is all you should have to do.

[tirwin]

Excellent. I just wanted to confirm before I button everything back up. Leaving on a business trip. Let’s hope I don’t forget anything between now and the weekend. There could be a lot of sake involved between now and then.

[J. Perrault]

Hey guys, bringing this thread back yet again.

I've got an '82 SC with a factory alarm and would like to remove the alarm, so I'm starting to sharpen the axe. Hopefully time frees up next week.

Reading the thread I got in the weeds toward the end.

Am I correct that the end result was:

-Jumper 61 & 61 at the alarm control unit ?

-Disconnect all others ( 15, 30, HN, MK, T, K1, 31 and E/A) ?

-15 and 30 does NOT need to go through the Alarm control unit, and can thus be disconnected ?


Incidentally, In my Bentley 911 SC '78-'83, there is an 87a in place of k1 in Tim's red and blue diagram above.

I may not respond right away, but any guidance is appreciated. Thanks for this thread Tim, rattlsnak if your still out there, and the others Pelicans.
-Josh P

[rattlsnak]

Correct

[J. Perrault]

Excellent, thanks rattlsnak
Sorry for the last reply.
-Josh P

[J. Perrault]

* late reply

[bobs1989]

Originally Posted by J. Perrault

Hey guys, bringing this thread back yet again.

I've got an '82 SC with a factory alarm and would like to remove the alarm, so I'm starting to sharpen the axe. Hopefully time frees up next week.

Reading the thread I got in the weeds toward the end.

Am I correct that the end result was:

-Jumper 61 & 61 at the alarm control unit ?

-Disconnect all others ( 15, 30, HN, MK, T, K1, 31 and E/A) ?

-15 and 30 does NOT need to go through the Alarm control unit, and can thus be disconnected ?


Incidentally, In my Bentley 911 SC '78-'83, there is an 87a in place of k1 in Tim's red and blue diagram above.

I may not respond right away, but any guidance is appreciated. Thanks for this thread Tim, rattlsnak if your still out there, and the others Pelicans.
-Josh P

J. Any chance you could clarify for me what jumps to where and does the connector just sit there then ?