Adrian, sorry I was unclear. The split second flash of the lights I was refering to was the warning lights not the headlights. That scenario does seem a bit more scary. Thanks, Don

 

Dear Don,
Slight difference in use of words and their meaning. When somebody says flash the lights I immediately think headlights.
The flashing of the warn lights and ALL of them does suggest to me a power wiring problem. Takes me back to the central informer and the power circuit. I am seeing the central informer being told that the ignition key is in a position it is not. It is only the central informer which can turn all the lights on and this is a specific function "warn lights test". Therefore the test function is being activated whilst the engine is running. I ammend my advice to start at the two plug connections of the central informer. Pull them out and check for damage, corrosion and the link to the the ignition switch output.
As I am sure you know if you run your engine in the dark and open the engine lid you will easily see if you have any sparks flying around. However this should only affect the engine, ABS, rear spoiler functions. It should not impact the warn systems located in the front of the RS America.
Ciao,
Adrian
964C4

 

Dear Jon,
I recommend you remove the left seat and inspect the harness from the DME going rearwards. You should also inspect the harness in the engine bay where it goes through the rear firewall. I suspect you have damaged wiring (chaffed). I have helped two people recently with similar problems and both ended up being the DME harness. The first it was up front because they had damaged the harness due to replacing the seats and the second one (typical) ended up being at the rear in the engine bay where a connector had been damaged by really hot air from a revised exhaust system.
I assume you have eliminated the ignition switch and ignition problems in the engine bay.
The apparent down on power and the check engine light and the warn lights certainly suggests interference with the DME.
The other thing to look at is the airflow sensor connector. Check to see that the plug is okay. Yours should be modified but the loom itself if it has been disturbed may be chaffing.
It is quite normal for these problems to disappear when you take them to the mechanic this is why I suspect wiring because wiring filaure issues rarely occur when the car is standing still at the garage when everyone pours over it. It may sound silly but may I also suggest you jump up and down in the drivers seat to try and reproduce the problem.
Ciao,
Adrian
964C4

 

Jon,

I do not know specifically about the 964 DME, but the 993s DME unit requires a very tight range of voltage to operate properly. I had a very similar problem to yours when I bought my car. Also, my radio would turn on and off randomly. Turned out to be a battery that was low on voltage. It had enough to start the car and drive without a glitch, but the electronics were not happy.

Good luck.

 

Dear Jon,
This is the warning buzzer in a confused state. It is controlled by the central informer and I suspect it was somewhat overloaded.
I always get nervous when people tell me that things stick in the seat and they sort of overpower it. The harness only needs to get snageed by something hard and the wiring gets cut up.
The only way to find out is to pull the seat and check it out.
I also recommend you check the harness at the rear firewall both sides.

The DME requires a reasonable tight range of voltages internally but it will still work down to circa 9V. The ABS low voltage warn is 9.9V. If the 964 DME runs out of volts it will stall the engine.
Ciao,
Adrian
964C4

 

Jon and Don - did you resolve the problem?? Share with us if you did! Thanks.

 

Greetings,

Unfortunately I do not have an answer yet. I did check the obvious like the ignition switch and cracked wires. The RSA is also in for the winter and before that it did not flash the lights for a few drives. I do not use this car on an everyday basis so it has not been a high priority. Will keep you posted.

Best,

Don

 

I had threee plug wires ends that went bad/got damaged during a rebuild. I was told they used a scope to find this problem. Not sure what ascope is or if you have access to one. They replaced my plug wires and my car is totally normal again.

 

Aha! Another plug wire victim.........Hmmmmm.

 

I'm back to getting all the dash lights and warning tone. Probably never went away in the first place. So now I have the distributor caps and rotors replaced, and checked all sensors operating ranges with a multimeter per tech specs and Adrian's manual. No problems there.

I did swap out the coil connectors to see if there was a difference between each set of spark wires. There was a difference running on one set versus the other. This suggests to me I am getting closer to the solution. I have set of plugs and wires tobe installed next.

Jon

 

Dear Don,
Slide under the dash and check the central informer. Make sure the connectors are properly seated in the informer. There are two connectors. I have a sneaking suspicion that your problem may be the central informer. There have been a coupe of other failures recently of this unit. Unfortunately caused by other factors but that is the way sometimes.
Ciao,
Adrian
964C4

 

Have you checked the voltage with the engine at speed? My Mercedes developed numerous electrical problems, and the root cause was a failed voltage regulator. Above 3000 RPM the voltage at the battery was 18.5 Volts. Everything went back to normal after replacing the alternator. The battery is still fine, and that was three years ago. Go figure.

 

Hi

I wass the other person having the problem the same time a J-macdonald. Solved by running the engine in the dark and looking for the arcing coil wire.

My Xmas tree effect only happened when I had the headlights on, so it is different in every case. If you have eliminated the key, then start on the distributor caps, as you can do this yourself. Mine were heavily scarred where the arc was jumping off the contact. If both dist caps are clean with no heavy lines near the contacts then I would look at your spark plugs and boots.

This is starting with the easily accessable, moving to the harder to reach item.

Good luck

Rob
91 964 cab
Jersey

 

Are you sure the fan is turning on. I had a problem in mine where the ceramic/series resistor (part no. 993 616 521 00) was broken and the fan did not turn on. A bit difficult to get to since it is in the front right bumper... well... I did not wanted to take too much stuff out, that could have been part of the complication... maybe if I had removed the front bumper it would had been easier). As a safety precaution I also replaced the fan relay.

Keep us posted on the progress!

 

Yes.

I removed the front right wheel, removed the black plastic cover, bottom tray, the shroud, and started by cleaning all the dirt that was there...

Let me see if I kept photos of when I did that...