skene

Be a bit careful with the silver stuff, since it's electrically conductive as well as thermally. As long as you don't get it on anything other then between the the heatsink and the transistor, it should be fine to use.

VWaddict

I was afraid of that. -Since there's vibration to be considered in this application, I'd say DON'T use it, because that stuff might creep/migrate with heating/cooling cycles and bumpy roads.

Keith

alordofchaos

Thanks, glad I asked - I was about to do something very stupid!

testarossa_td

http://www.arcticsilver.com/

VWaddict

Actually, that looks like good stuff. I'm sure that its thermal transfer characteristics are very good; they seem to know what they're making.

A good and apparently unbiased comparison here: http://www.heatsink-guide.com/compound.htm

-Having said that, if these DMEs were assembled without any compound (which is quite possible, I mean they're not under massive thermal stress) then ANYTHING will improve reliability, and after 20 years I'd have expected whatever was on there to have dried up at least a little... and more likely quite a lot.

I did also find quite a number of hits when I searched for 'electrically conductive heatsink compound' some of which were forum posts by people who'd damaged stuff with incautious application of Arctic silver... for example, the first hit was: http://www.xtremesystems.org/forums/...ad.php?t=13742

Anyhow, in the TO3 heatsinking game, I only ever see the regular white heatsink compound used, and in this case I'd definately recommend against Arctic Silver anywhere near an insulated TO3, though I must confess, I'm tempted to get some for a couple of hot-running CPUs here at work!

Keith

gregeast

At the almost certain risk of jinxing myself, I declare victory!

It's been two weeks since I resoldered the leads on the transistor on the DME and the car has not died since then. The problem had been increasing in frequency and on the day I resoldered it had died 3-4 times, so (fingers crossed), problem solved :-)

toddk911

Still ok????

I just had this happen.

Oh, and that transistor is the injector driver, as I am told.

Would not running ballost resistors on bigger injectors increase the temps of the transistor???

gregeast

Yep, still ok. It's been just over a year now and I've not had it happen again. I probably have some higher res pics on my hard drive somewhere if that would help, let me know & I'll email them to you.

Yabo

Really don't think it's the injector driver. Pretty positive it is the coil driver, as when those solder's are bad, you won't get a flash from the timing light (meaning no spark)!

Did this a few months ago, been fine ever since.

greenshoes3

where is the dme relay located on late cars?

TT

The transistor pictured at the beginning of the thread is the ignition driver.

Adding a ballast resistor reduces the current going through the transistor, reducing the temperature.

gregeast

DME relay is in the fuse box, DME itself is located under the front floorboard on the passenger side.

Fishey

So I am going to be honest, I never really fine anything relivent to myself here on rennlist in terms of repair.

However, I had this problem today and litterally got on here to just browse and came across this thread. Now, I would have fixed the problem by replacing the DME unit as a whole with one of my spares but I would have to drive the the shop and back tommorow. Since I found this post now I don't have too. I fixed the two broken solder points and all fixed no more engine shutoff.

Thanks alot
Ronald

P.S. Good Thread!

coilbox

My DME cant control IDLE, its not the electrovalve or the cables. Any clue what to look for?

inactiveuser92616

Greg, thank you for the thread! My 944 has been dead at work since last monday night, and tonight I was able to fix it thanks to your instructions.

Anyone want to buy a 944?