Captain_Slow

Alan - I was only able to do it because of responses you have provided in my thread or posts you made to threads I found helpful (Your off the cuff directions for removing the panel were extremely helpful). When it comes to electrical stuff, a compliment from you means a lot. I'm sure a lot of owners have done this job - thumbs up to them.

Wow! Those stickers air-cooled posted are fantastic! No worries, the tape is gone and I used an overhead projector pen (cleans off with water) for the green letters.

My motives for the thread were to remove some of the fear and mystery surrounding the CE panel. Pictures of the process help the most. I also want to document the work I've done on my car in a public space. Full disclosure is a Google search away if/when I sell the car. However, the more I pour myself into the projects and improve the car, the less I want to part with it. Thanks again for the critical assistance you provide in this forum.

Captain_Slow

Bertrand - thanks for posting Alan's CE panel diagram...That's going to be printed and laminated and attached to the panel lid.

Kiln_Red

The customer replaced the fan controller with a used one offered by James Morrison, or so that was the story. I haven't seen the car again, nor can I attest to the quality of the fuses as they were the fuses that were provided by the donor block.

According to the customer, the new-to-the-car fan controller was the solution. I have seen stranger things.

Captain_Slow

Was the fan problem associated with burned 28 and 29 fuse holders, or were other cooling fan system components the cause of the problem?

The fan controller by the passenger seat is rarely the problem. The Final Stage output controller (a square wave pulse modulation device that delivers the "pushes" to adjust the fan speeds) can cause problems. The PO of my car replaced the controller (brain) next to the passenger seat. I replaced it again (foolish). I replaced the Final Stage with a rebuilt one (shipped all the way from Netherlands...foolish)...and problem remained (fans ran in failure mode...cycling). It was NOT my fuses as they were new when I checked them soon after buying the car. But these new fuses were masking the problem (poor fuse holder contacts). I never got it in my head that #28 and 29 had a history of bad fuse holder/fuse contact condition. One day I randomly thought...I'll put new fuses in and spray some Deoxit in the fuse holders. The fans worked perfectly for more than a year. Until I used the AC a lot this past August. Melted fuses - but never blown. All of the trouble was the bad fuse contacts, degraded by heat, oxidation, and probably some loosening of the grip on the fuse spades.

Once a fuse starts to heat up it's a runaway effect, as heating increases the resistance...and the temperature shoots up. Thus current is reduced as the hot fuse spades become significant resistors. The plastic casing melts with an intact filament inside. The controller next to the passenger seat won't see what it's looking for - a certain voltage or amperage (I can't recall which). It's a tight window within which the controller is happy.

Even the combined oxidation throughout the entire cooling fan system connections and grounds can make the controller suspect a fault in a fan or both fans. But in my case, I cleaned the grounds and connections with DeoxIT and still the fans cycled through fail mode as soon as the engine warmed up....Until I turned my attention to the fuse holders and discovered the charred plastic and discolored and degraded fuse holder contacts.

My conclusion - Alan is right. The problem was all in the poor contacts at 28 and 29. And I suspect it started out gradually several years ago, but as the condition of the contacts deteriorated more and more, the time from cool fuse to very hot fuse shortened until I found melted fuses after 40 minute drive with the AC on. AC keeps the fans running constantly...great for heating up fuses with poor contacts.

Kiln_Red

Certainly, Alan's explanation is the only one that makes sense and I do defer to him on 928 electrics. Come to think of it, I wouldn't hesitate to enlist his help with any auto electrics.

In the case of the car I was referring to, it was the 28 and 29 holders that burned out. This was four years ago. My recollection may not be the best as I recall that what I originally referred to as the fan controller was in fact the final stage controller, as you refer to it.

What he said was that the replacement fuse holder also melted and that the issue wasn't resolved until the final stage controller was replaced.

Most likely is that the fuses were marginal on both blocks. The underlying issue was in fact the final stage module. If the replacement module failed in the same way, it would now blow the fuses long before the holders were melted so long as the fuses were of appropriate quality.

The only issue I have with that is with the fact that, in my experience, unordinary current flow can give circuits fits. Higher amperage is but just one issue. Current flow durations matter too.

simos

The cooling fan motors will also draw more current when bearings gets older and do not turn as freely as before. Also other possible dirt will make them more sticky.
There is fan motor reconditioning write up available on Theo's web site: http://jenniskens.livedsl.nl/Technic...Garmonsway.pdf

Alan

Yes accepted - BUT - That just means they become more likely to blow the fuse. For this kind of problem to start - and to continue to progress to complete failure - you need a fuse terminal connection issue - one of the several things I noted (or combinations of these).

Failing controller or final stages can't provoke that - there has to be a latent issue already. Current isn't really a cause here - contact Resistance is the cause.

Alan

merchauser

BUMP: some threads should be read by all of us over and over. this one is amazing, and exactly what I need to do
thanks to captain slow, and alan (and others) for a thorough and concise write up! BUMP

Captain_Slow

Thanks Merchauser - Glad to help. Remember, the old plastic will be somewhat brittle. I worked on mine in a warm garage and I think it helped a little. After you get a donor panel take time to practice using the picks to remove a few blocks you don't need so you refine your technique. Also, check your HVAC blower fuse socket for signs of heating and avoid practicing on that one on the donor panel...you will want to use it to replace the one on your panel. At first it seems like a real challenge to remove the blocks, but after practicing a few times you develop a technique that works well with minimal cracking. Patience and not forcing are key.

You've taken the deep dive into your maintenance chores and making great progress!

jpitman2

To ease removal of connectors of many sizes in cars, get one of these...
https://www.ebay.com/itm/18X-Car-Wir...-/153220870940
Especially useful for round pin and socket connector removal, when you dont have the correct size brass tube.
Now I know whats behind the late fuse holders!
jp 83 Euro S AT 57k

merchauser

just ordered a set thanks

Landseer

Kudos Jon,
Thanks for the good descriptions and pictures. Plus to all others who contributed. Concepts like bearings going bad in fan motors also helped.

I've removed the faceplates and cleaned the fuse folders on 86 car. It's going to make a huge difference.