Corrosion in the Motronic box

[-84 Carrera]

Hi guys,
To make the wait for spring a little bit easier to endure, I like to spend some of my spare time in the garage going over different areas of my car. Tonight I took out the Motronic box to have a look, and I wasn't to pleased with what I found...


The car was running fine when I put it away in November and I have no reason to belive there is a problem now. What I would like to know is if I should be worried?

Thanks

/Claes

[Peter Zimmermann]

Because I'm not, and have never claimed to be, an electronic kinda guy, I can offer one comment. That is, many years ago we had a beautiful, metallic brown SC coupe towed to our shop from a subterranean garage that had flooded. The water inside the car had reached the bottom of the seats, so we loosened the rubber boot between the nose of the trans and the tunnel, jacked up the front end as high as we could get it, opened the doors and let the car sit in the sun. And then an adjuster from Farmer's Ins showed up, took one look under the passenger front seat, saw the wet Lambda ECU, and totaled the car.

I asked him, "Are you kidding me?" I told him the car was fixable and would not have future problems. He looked me in the eye, said that it was company policy to total any car with wet electronics, and drove away.

I tried my best to buy that car, but it went to auction and I'm sure some wrecking yard that bought it laughed all the way to the bank.

So, wet electronics. I would start with an aerosol electrical contact cleaner, then I would call someone experienced with 911 ECUs who can run pin checks, maybe even solder/replace anything critical. Good luck with it!

[KNS]

To add to what Peter has said and what 'ianc' is going through with his car in another thread: Think twice before calling your insurance company if your P car gets more than a little wet. It might be worth it in the long run to fix your wet car out of pocket. If it's your daily driver hack, well then, that's different.

[-84 Carrera]

I don't know at what point in the 25 year history of the car that it was wet. I have owned it for one year and I haven't seen any other signs of corrosion or moisture related damage. If the car works now and stays dry, does this issue need to be adressed?

/C

[steely]

I think you may infer from Pete's answer that this might be the case - the brains got wet at some point. The card does look like something happened. in the industry I work in, we once had a plumbing leak in a ceiling which wet some electronics. We found over time that the devices exhibited problems in some cases soon afterward - depending on the type of circuits/materials involved. As they dried, whatever it was in this case created a small crystalline precipitate which was slightly conductive - and which made small low current shorts. This occurred over weeks. If you don't have a prob now, you might be ok - but if you can, check underneath the board too.

In our case, the boards were washed somehow and thoroughly dried but I am sorry I don't know what product or technique was used. Most everything returned to normal.

To your question, you might just keep an eye on things in the future in case you get a strange problem, but pursue investigating something along the lines that Pete mentioned. You might photograph the board too in case whatever you wind up using on the board also removes any lettering, or use it to baseline against any eventual progressive change you could observe.

It doesn't sound time critical your case, but I wouldn't ignore it completely.

[Canada Kev]

Back in about 1991, I was leaving on a little vacation and watered some plants before I left. This one particular plant was on a shelf above my TV. As I poured the water over the dirt, it started running out the bottom of the pot, across the shelf and into the top of the TV. It instantly buzzed and went blank. Crap. Well, I didn't have the time to ***** about the loss, so I left it as it was. A week later when I got home, I turned on the TV and it fired right up. It was still working when I gave it to a buddy. This was two years ago.

That piece of electronics still worked over 15 years after getting doused with salt and mineral filled water. I'm not saying that your DME will be like this, but if it is working and is now in a dry environment, then you might be able to get away with doing nothing. I would keep an eye on things, but it might be just fine.

[Peter Zimmermann]

I think that my primary concern is that all of those little, corroded, rusty electronic bits co-exist with vibration. In a TV a rusty resistor might outlive the rest of the TV, but in a car a different environment works against you.

Think about broken cylinder head studs on early SCs. At some point in time after corrosion hits, bang, the stud breaks. Without the constant stress of the stud being stretched (by torque), and vibration, they might last three times as long.

[der Mond]

Pete, do you know where I might look for a schematic circuit diagram for a '87 - '89 Motronic DME unit?

[Peter Zimmermann]

Originally Posted by der Mond

Pete, do you know where I might look for a schematic circuit diagram for a '87 - '89 Motronic DME unit?

Greetings, stranger! I have never seen a schematic for those ECUs, but there are posters here, and on Rennlist, who live inside those mysterious boxes and might offer to help. Try starting a new thread and maybe one, or more, of the electronics guys will answer. Good luck, and I hope that all is well with you!

[scottb]

Since you've got the box out of the car, you might consider using some contact cleaner spray (that doesn't leave a residue) and a soft toothbrush to carefully clean the circuit board. I suspect that much of what you see will clean up easily. Once you've cleaned it up, you can use a magnifying glass to check for solder joints that look potentially problematical.

My $.02.

Scott

[ibeaudoin]

Back in the 80s-90s I was working in a shop fixing cellular phones. I fixed a lot of phone that were water damaged. And it worked. Here's how.

1- Disconnect the power asap.
2- Disconnect your DME and open it.
3- If there's still water in it, take a hair dryer or spray air with a compressor and remove the water.
4- Spray the board with WD-40. Yes WD-40!
5- Use a small brush, like a toothbrush and clean the board with it and the WD-40
6- Take some rags and carefully remove the WD-40 from the board. You might also want to spray some air with a compressor to remove any WD-40 trapped under components.
7- Also check the DME connectors (On the board and in the car) Clean with a small brush and little bit of WD-40.

I saved dozen of cell phones like this, also saved my ABS computer in my 87 635csi 2 years ago the same way.
Hope this help.

[CCM911]

I went through a huge puddle at Pocono about seven years ago, and my car took on a bunch of water. During the last run session it started to run funny and then stalled. We finally got it going and I made it back home with no further problems. Later that night, the car stalled again, so I let it sit for a week. It has run fine since.

When I ran this by my mechanic, he said it was hit or miss, regarding permanent damage. In my case, it was luckily, a miss. But when my buddy had the same thing happen, he had to replace his DME.

Bottom line. I would venture to guess that if you had no running issues to date, you should be fine. Just my opinion, so take it with a grain of salt.

[Canada Kev]

Originally Posted by Peter Zimmermann

I think that my primary concern is that all of those little, corroded, rusty electronic bits co-exist with vibration. In a TV a rusty resistor might outlive the rest of the TV, but in a car a different environment works against you.

Think about broken cylinder head studs on early SCs. At some point in time after corrosion hits, bang, the stud breaks. Without the constant stress of the stud being stretched (by torque), and vibration, they might last three times as long.

Yeah, you have a valid point, there. And I should know better. I work with electronic stuff every day. Mind you, they don't get wet, just large EM fields and lightning strikes...

[der Mond]

Pete and the rest of you, between Chris Bennet from Pelican and some other great Pelican guys, I got the DME schematics and I also got from ECU Doctors their DME Diagnostic Chart. If you'd like, send a PM or email...

[-84 Carrera]

Thanks all for your input. I spoke to Porsche Sweden, a new unit (factory refurbished) would cost me about 3000 USD. I decided to have a go at cleaning it. I went to my local electronics supply shop and bought a pen shaped stiff fibreglass brush, some spray on contact cleaner, a magnifying glass and air in a can. It took a few hours to complete, but as it turned out the rust was mostly superficial stains. I am really happy with the result. As I was anxious to get it back in the car to try it I forgot to take after pics, sorry... Thanks for your time and effort.

/Claes

[HawgRyder]

In the Electronics industry...we use Isopropyl Alchohol and a soft to medium brush to clean the boards.
Use care with any components that are vertical to the board (stick up)....make sure to get under all resistors and capacitors if you can.
If the unit checks out after the cleaning, you can spray it with conformal coating to reduce the probability of future moisture problems.
Also...use a magnifying glass and check the solder joints carefully...top and bottom of the board.
If in doubt....re-heat the joint and add just a touch of new solder to make it run....do not over-heat the component.
Bob

[kidrock]

I would also recommend a light, thorough cleaning.

IIRC, there's a guy in Florida that supposedly does top-notch work on Motronic. Also sells used units for considerably less than half than what you were quoted from Sweden. I have his link around here somewhere, and he comes highly recommended by other Pelicans. I'm surprised nobody has chimed in on this yet.

[chateau]

Ingo Schmitz checked out mine and he does a great job at reasonable prices with plenty of after sales service.

[rusnak]

Ingo is approaching sainthood in the 3.2 no start threads.

Is it ok to ask someone to post his company or contact info?

[ischmitz]

I appreciate all the nice comments. If you need help with your box contact me via PM or send me an email to 3.6@cox.net.

I agree with what other said - cleaning with IPA or WD40 is a good idea. Then like modern circuit boards coat the boards with conformal coatings such as HumiSeal. It is somewhat like a very thin clear acrylic or polyurethane paint that prevents humidity from getting to the components. Any analog board with resistor values larger than 1 MOhm requires this to prevent component drift. It will greatly prolong life of the unit and might even protect against immersion.

Bosch used to build water-tight DME computers in the past. The last went into the early BMW and early Porsche 944. After that they went to the sheetmetal housings and the boards are exposed to humidity and water in the event of flooding. Some boards in these DME's have some wax or varnish that protects against humidity but I have seen many trashed units that got wet.

Cheers,
Ingo