washington951

(cross-post)

hi folks. i have tracked down my intermittent, hard cut-out problem to the DME. after having it die a couple times last night, i gave the floorboard on the passenger side a good WHACK and the engine died.

got access to the DME and noticed two things:

-it was loose on the mounting points
-it was pretty dang hot.

i tightened up the mounting points and it seemed to cut down on the cutting-out, but didn't completely cure it.

do they normally run hot?

anyway - i have it in my head that these can be taken apart and resoldered like the cruise control brains can. possible, or should i just replace it? anything else i should do while i'm down in there??

a note: it was strange that going over bumps doesn't seem to really cause things to cut out. hit some bumps and it may cruise right along - rolling along on smooth pavement and it may cut out two or three times unprovoked. straaaaange!!!

awilson40

There is a common problem with poor / broken solder connections.
I would remove it. Open it up and carefully check and re solder where
you think it needs it.

washington951

cool - just wanted to make sure that i had it in my head correctly. there are obviously some bad connections/cold solder joints in there somewhere. can't hurt to put the iron on em and let the solder run again.
thanks.

Tom M'Guinn

I did the same on an old rx7 brain, and it ran for years. I really bright light and a magnifying glass helps a lot when inspecting the circuit board solder points. Sometimes, bad joints appear as nothing more than faint grey lines around the base of the solder joint. Don't forget to check the solder joints holding the main connectors to the mother boards, and for that matter make sure to check the connectors themselves and the pins in the connectors. At least you know where the problem is now. Worst case, Vertex sells rebuilt DME's.

washington951

tom - thanks for the input. i'm always happy to see one of your replies here.

i had great success re-soldering the cruise control brain on my previous 951. hopefully this will go the same direction!

Ski

I have two spare DME's and would be willing to part with one if you need it, let me know after soldering.'

There also seem to be two good ones on ebay and one I don't trust the seller from his wording.

washington951

ski - thank you sir, i might take you up on one of those if my soldering efforts prove futile.

Andrew Wojteczko

There is a TO3 style component standing on its side on the right side of the DME. It has 3 long legs that go to the board. You will find that the solder has aged and cracked around the pins as they pass through the board. Look at the solder joint through a magnifine glass. Resolder these three joints and your problem should go away.

washington951

andrew - excellent. i appreciate the detail.
oh - and thanks to the list for tolerating my x-post between here and the 944 board. some folks don't frequent both places and i have gotten a wealth of info from each thread.

moocho-grassy-***!

H2Opumpr

Andrew is right. The same thing happened to me on the way back from Laguna Seca. Took apart the DME and took the two halves of the DME to a TV repair guy. 25 bucks later all is well. I had roughly 50 solder cracks... the worst being the joints that Andrew mentioned. And yes they do run hot... especially when I had Autothority chips in there.

good luck

fast951

When you lose power, do your gauges go blank as if you switched the car off? Or you can see the lights?

Magown

I've resoldered 4 DME's. So far out of the 4 only 1 has had problems, it lasted 1 year, needs to be done again. If you want to send it to me, I'll be glad to give it a try.

washington951

guys - it was pretty warm, thats for sure, so maybe its a 'quality' of the autothority chips. thinking about changing those...in a way, i hope that i have a lot of obvious cracks!!

when it dies, nothing changes except that the engine isn't running anymore! on the highway, i simply push the clutch and then turn the key off, then re-start. starts right up. match revs, and away we go.

stephen - i'll have a go with it - i'm pretty good with an iron (i'm sure i just jinxed myself...) but if i have problems i'll PM you and give you a shot! i really appreciate the offer there, speedwag!!!

washington951

ok - got in there and resoldered a few of the spots that looked bad. it DID improve the situation, but didn't completely eliminate it. i guess its back in to hit it again.....

Perry 951

Brian -

Carefully re-solder ALL of the pins for the harness connector... I'd bet that is your problem. Think about it, how many times has that DME been out? (chips, MAF wiring, and who knows what else)


I would grab a cheap Radio Shack de-soldering tool and start with fresh tin. I fought with my OEM unit for a few months after I bought the car, and I ended up re-doing every joint in it. All was good until that pesky flame up.