tveltman

I finally got around to tracing down the last bit of my battery drain. With all doors opened and then closed (with ignition off), the drain is around 100 mA. Removing plug E kills the drain to 4 mA, so I thought I'd just disconnect E for a while, unfortunately, this kills the radio (I have an aftermarket install). So I thought I'd go into the glovebox and see what I could find. I disconnected the radio, and this didn't make one lick of difference, but when I disconnected the alarm module, presto, current drain is gone. I tried jumpering 30 to 87a (mine is an '88), but the car wouldn't start. I thought that this was the way you were supposed to bypass the alarm, but for some reason, it doesn't work.

So, I have two questions:

1. Is it possible to bypass the alarm (I know it should be) by some other means, and if so, how is it done? Or did I just misremember and do it improperly?


2. Does anyone have any suggestions on how to actually FIX the drain. Presumably the factory alarm isn't supposed to draw 100 mA by itself. Are there trouble spots that I should check first? Has anyone encountered a similar situation?

Ideally I would prefer to keep the alarm intact, but honestly it isn't that big of a deal. If I have to troll through the wiring all throughout the car in the hopes of finding the piece of wire with broken insulation or whatever, it would probably be better just to neuter the alarm, hence question #1.

Thanks in advance!

SteveG

A quick search (not all are) on "disable alarm" brought this up:
https://rennlist.com/forums/928-foru...f-problem.html

Alan

On the alarm unit plug bridge terminals 15 -> 87a the Black/Red & Yellow wires on the pigtail.

Alan

vanster

I disconnected my alarm thanks to the wonderful instructions here on RL.
My '80 was simple. Now as least I can lock my car.

Alan

BTW obviously the alarm drain should be lower - I'd check that all the other connections look OK functionally.

The alarm takes more current when it is armed - but <<50mA (more like 15-20 mA) but consumes much more when its actually alarming... it isn't is it? sometimes folks cut wires to pesky things like loud horns...

When connected have you tested the alarm to see if it actually works? - from all trigger sources?

Alan

tveltman

No but I know the horns work, so the alarm will sound if it is going off

Alan

The alarm has a different horn...

Alan

tveltman

Hmm. Where is the alarm horn located? I'll check it out right away.

Alan

I believe on some years it is down beside the HVAC blower motor (under the cowl beneath the windshield) - and on other years its actually inside the HVAC airbox (inside the car).

For obvious reasons it is not easily accessible... Its probably easiest to just test the alarm - lock a door with the arming key & a window open - reach in and unlock/open door => alarm alert

Note there is an ~10-15 second arming delay

Alan

tveltman

Okay. I've decided that if the horns aren't accessible, and the current drain is caused by the alarm, and it's possible for the alarm to leave me stranded on the side of the road, I will just disable the alarm and call it a day. That leaves me room for a keyless entry system besides. I don't think anyone is going to steal my 23 year old porsche, and if they do, I'll put the insurance money towards a cayman.

Thanks everyone for the help, especially you Alan.

Landseer

Disable is easy, as mentioned. Wiring diagram clearly shows it.
Connect the thin red/black wire with the thicker yellow wire.
Can be done at the flat 8 pin connector tucked behind CE panel.
Should be no need to remove the alarm module

Horn is accessible by removing blower fan.
I wouldn't think its the source of draw, especially since it works.
I'd not bother it.

Fixing draw? Usual suspects are hatch pin switch & door pin switches.
Cleaning should be done on all these cars! One of the first things we do now when a new one comes home.
To fix, remove, disassemble, polish and resolder onto the brown/white wire.
Look for brown/white wire insulation shorts.
Clean the rusty door post threads (switch threads are stainless, but the door posts get rusty)
That usually removes the power draw. 5 out of 5 cars for me.

But the alarm may still alarm at the wrong time. In that case, the job gets big quick.
To solve requires microsurgery on the backs of each lock at the alarm contact.
They get pretty gunked up, especially if conductive lube was used in lock.
If/when somebody sprays **** into a lock to clean it, this is where it ends-up.
Then, they misbehave, either shorting, not making contact when the should, from an electrical perspective getting out of sequence with each other.
Or, as seen in pictures below, they can wear and it becomes a combination effect.
PITA to fix, but it is definitely doable.

Once you visualize the alarm as door pins + lock contacts, and unlocking/locking circuit (mechanical effect) it gets pretty simple.

That said, I've not been patient. I've disabled 4 cars and left alarm only on 1. It needs lock contact cleaning. Its not drawing anymore, since pin cleaning. The lock on one side of the car actuates properly when you turn the key in the other side.

But still sets off alarm. Reason is that even though the door locks are cycling, the alarm contacts in the passenger door don't seem to make electrical contact unless key is used on that door, putting a little more pressure on the contacts. I've fixed these on several other cars, but haven't got to this one yet. I know exactly how to fix it, but choose instead to let my lazy *** surf the internet instead of apply real effort to get it done.

Landseer

Pictures, FWIW

tveltman

Wow! This thread should be saved just for that description and those pics.

Landseer

As confident as I am with the solution, somebody will come behind.

And they will add more value, maybe even disputing some of my approach!

Kind of the nature of rennlist when there are so many smart people involved in 928's.


Certain things are very hard to troubleshoot. 928 electrical takes the cake. Sometimes its best to go with the shotgun, knowing you are shooting a tight pattern, up close.