pmalenfa

Hello,

I wonder if someone had this before. I bought a 964 (1991 C4 cabriolet) about two weeks ago and I had the following problem twice already:

- All "in dash" lights camed on. I mean all warning lights + beeper (not the buzzer for open door)
- This happenned once when slowly cruising (around 30 mph) and once on the highway
- The reset button does nothing, I have to stop, and restart the car (reboot!)
- This has no mechanical impact, no ignition cut-off, all gages works fine, just the warning lights in dash (all)

It look like a computer, wiring or ground issue, does anyone had seen this?

Thanks

Pierre

augsburg911

This sounds like the Christmas tree effect.

springer3

Many have. Do a search under "christmas tree". You have an electrical breakdown on the high-voltage side of the ignition system - spark plug wires and ignition coils cause this when they start sparking and scramble the engine control computer. It will get worse with time, and I am sure there is stress on some expensive electronics. Do not think the "no mechanical problems" will last. If the wires and coils are old enough to vote, it might be a sign you got your money's worth out of them.

Henry964

I had the same issue a year and a half ago, new Bosch ignition coils solved the problem, but this year I also changed plug wires (they were in bad shape) just to be sure

964TURBOCHAS

This happened years ago on my 1990 964
It was caused by the plug wires and ignition coils sparking..........it would get really bad in rainy weather.
Once changed out I was good to go...

scott 964

+1

klr10

New HT coils and take a look at your leads, Ditributor caps and rotor arms. But seems to be most likely a bad HT coil.

jembolt

Plug wires in my case - after spending hours checking everything else.

pmalenfa

Many thanks to all of you for the posts. I will have this checked and will let know the results. Thanks again!

Pierre

pmalenfa

Hello again,

I ordered and received new coils (bosh, from autopartsway.ca, 130$CDN for both with taxes). I just tough I would replace them myself because from what I saw in other threads, it looked quite simple.

But now, after looking at the steps, I'm not sure. I'm a porsche newbie... So before I either decide to do it myself or send it to the garage, I have a few questions for thoses who already did this.

- Does the coils can be replaced without removing the heat exchanger and/or the fuses box?
- Can the coils be slided out and back in the coils assembly just by loosening the 2 allen head screws?
- Or do I have to completely remove the allen head screws?
- If I need to remove the heat exchanger or the fuses box, does anybody have the procedure?

If it gets complicated, I'll bring it to the garage cause I'm not well equiped at home...

Thanks guys!

Crystal Cranks

It's not to big a job, you do not have to remove the fuse box or the heat exchanger all I removed was the rear blower motor (two bolts and a bit of piping) Just don't drop anything down the hole left by the removed piping, don't ask
Do a search on it there is a few threads on it, go on give it a go you know you what to. If you get stuck there are plenty of people here that will help.

Rocket Rob

- Does the coils can be replaced without removing the heat exchanger and/or the fuses box? You need to remove the heater blower and engine fuse box
- Can the coils be slided out and back in the coils assembly just by loosening the 2 allen head screws? Doubt it. I removed the two allen screws and the bracket holding them in, swings out.
- Or do I have to completely remove the allen head screws? I removed my screws.
- If I need to remove the heat exchanger or the fuses box, does anybody have the procedure?

I just did this last weekend.

1) Remove the heater blower
2) Open the fuse box and remove the 3 10mm nuts
3) Pull the fuse box contents out of the box and remove the box itself. Now you can see the coils
4) Disconnect the power leads in front of the two coils
5) Unscrew the two electrical gizmos (I think they are resisters)
6) Unscrew the heat sink
7) Remove the two plastic covers over the tops of the coils. They are held on with a single plastic snap.
8) Unscrew the two allen screws holding the strap across the coils
9) Remove the coils. Note: Mine were resistant. I had to pull hard to brake them loose.
10) Unscrew the wires on the tops of the coils (8mm & 10mm). Be careful, there are washers under the nuts. Don't drop them like I did. Luckily, they are ferrous, so I was able to fish them out with my mechanics magnet.
11) Disconnect the high tension lead going to the distributor
12) Remove the second coil
13) Installation is the reverse.

Note: One of my coils looked brand new. The other had lots of corrosion around the high voltage lead. I suspect that was my "problem child".

I hope this helps and good luck on the repair.

darth

Pierre

One thing that wasn't mentioned yet is to disconnect the battery first. That should be the first thing you do whenever working on anything electrical and in fact it's good practice to disconnect the battery when working on anything on this car. There are a number of wires which are live (i.e always on) and not fused such as the starter, altenator etc.. If any of these wires touch a metal part on the engine or body they can carry a huge amount of current and cause melted insulation or worse case a fire. I'd also suggest take pictures before you take things apart, and label /bag parts, many times I wish I had as it would have saved a lot of time in the long run. When you're taking things apart and anxious just to get it fixed one overlooks suttle differences such as screws/bolts that look the same and when you put it back together you find out one bolt is slightly longer than the other or the order of spacers/washers / orientation in which they came off.

Bill

pmalenfa

Great advices and instructions guys! I'll give it a try then in a couple of days.

Thanks.

Pierre

Rally Guy

+1 on this proceedure. Done last night - about an hour - but I was slow, cautious and cleaned lots of stuff while I was in there. Also used this time to replace bad blower motor.

I did not (and see no reason to) remove the fuse box. I DID take off the cover - but I had no problems replacing coils with the fuse box in place. And frankly - I'd rather not disturb a rat's nest of 20 year wiring if I don't have to.

This is NOT a difficult proceedure. One tip..

When you remove the wires bolted to the Coils (8mm and 10mm deep sockets and 1/4 inch ratchet help alot) BEWARE that there are little washers on top of the ring connectors. Don't loose them.

I used a rare earth magnet to capture these before they fell down beside the engine. Coils are now installed - ready to go.

(OMG - I should have read the post above in detail - SAME approach to the washers).

Everything else is STILL apart - waiting on Fan bearing to put in new Alternator, fan bearing, belts.

I probably should have kept going and done the OPS o-ring fix too - but that's on the other side and I wasn't keen on taking the ENTIRE top of the engine apart when I'm itching to get driving again. That'll be a winter project.

RK