Kevin in Atlanta

and this is what I found:



I am not sure if the fuse was askew or the melting process pushed it out. I am just lucky the fuse did blow before doing much more damage.

I have sourced a replacement from a matching model year CE panel locally for the ruined fuse block.

Saddest part was the AC had never worked better before the puff.

The Forgotten On

I had that happen to my 81 however the fuse holder was fine. The rear wire, not so much. A puff f smoke and the car shut off, not fun.

I dealt with that and replaced the blower motor resistor pack, which I think was the problem and haven't had an issue since.

Also, make sure the fuse block you are using is the from the exact same position as the one you are replacing.

They are all different pin-outs and mixing them up could be catastrophic.

Alan

I doubt the fuse blew - it may have ripped apart from the mechanical stress - but in this case there was likely no electrical over-stress.

In each case damage like this is NOT related to over current - if the fuse body melts (as here) or the insulation of the fuse wire melts or if the fuse-holder melts (also as here) - The cause is a poor electrical connection with excess resistance. This can be excess oxidation, water corrosion, poor mechanical contact (loose terminals) or poor fuse blade plating quality (cheap Chinese fuses).

It is almost never excess current (in fact the opposite). I have never seen damage like this that was actually related to excess current.

Excess resistance in the circuit means the current will actually be lower than normal, the power delivered to the normal load will be lower still because the voltage at the load will also be reduced. At the site of the increased resistance voltage will be dropped and power will be dissipated very locally. This local heating will cause further contact degradation (a death spiral) - so these events get worse quite fast - right up to the point of actual failure.


It wasn't - it was just the wire connection to the fuse-holder terminal

This is a good warning for the later (1985+) cars - however it isn't sufficient.

ATC fuse-holders on the newer style panels vary by fuse block ID (they are all numbered - look underneath). BUT they also vary by year. The "pinouts" are the same and they look exactly the same - however there are internal connections between fuses on the input side that vary. BE VERY CAREFUL!!

Here is an example where all the input side connections are shorted together - there are many other possible configurations.

You must match what you had before - only the same numbered fuse block from the same year guarantees that (else you have to disassemble OR test both to ensure they match)



Alan

Kevin in Atlanta

Agreed ^^^^

I had this CE panel out 2 years ago to replace the fuse block that included the wipers. I cleaned the CE panel at that time and replaced fuses.

I'll know more after I pull the CE panel this week.

Kevin Wilson (GTS) had a similar experience with the cooling fan fuse blocks a year back. His 87 needed a complete wiring harness replacement when using the rear defroster for the first time melted the harness from the CE panel to the DS coil. We pulled the engine to replace it.

Kevin in Atlanta

I have access to a less charred 16-20 fuse block from a GTS. Seen here separated.



Obviously that is mostly unusable. so I looked for a good white fuse block I could source the back half and contacts (lower). I found 6-10 were in good nick. Shown before I treated the lower contacts a proper cleaning



Luckily, the upper contacts ( a single blade ) was undamaged. I swapped them in and after filing down the 16-20 fuse block cover reassembled it.

Kevin in Atlanta

Got a replacement 16-20 block from 928 Intl

Here's couple of pictures of the 91's 16-20 melted block.




right side of fuse block nearest blower motor fuse



grey wires scorched a little brown



new 16-20 block ready to go back in

Going to replace all the fuses, retreat the fuse panel.

Ducman82

resistance for sure.

Kevin in Atlanta

I kind of understand that, What I cannot understand is why after pulling every fuse, using scotchbrite and contact cleaner to treat them I still had a meltdown two years later. I assume the reason the two fuses did not blow is that the corrosion allowed the fuse to heat up and melt, but not blow the fuse.

Ducman82

i have run across this many times. its the cheap fuses. as alan said, the crap coating of the fuse blades just corrodes. and if you scrub them, they corrode faster. i had one customer who's fans were not working, it was due to resistance at the fuses. they were soooooo close to melting..... put good fuses in, problem solved.

Kevin in Atlanta

Well, I don't use cheap fuses, but I do clean them. Just bought a complete set of Eaton/Bussman fuses. I'll replace them all. $31 = cheap insurance.

GregBBRD

I think it is caused from the brass contacts not being tight enough on the blades of the fuse....I almost always remove the numbered cover and tighten down the brass contacts when I find a slightly overheated fuse.

Loose Connection=Resistance=Heat. (Exactly like Alan says, above.)

A simple squeeze with a pair of needle nose pliers quickly cures the problem, when the numbered cover is removed. (If the problem has been occurring for a long period of time, there will also be oxidation on the brass contacts, which needs to be removed.)

This is especially important to check on any of the 25 and 30 amps fuses, as there is enough current present to cause this overheating.

Captain_Slow

Exactly this...

Kevin in Atlanta

I replaced all the fuses, and the common relays. Marked them as '53' and the date I replaced them.

Chuck Schreiber

Just had this happen to the 79 on route to 3rd Coast.
2 miles out, Go figure..
Anyhoo.
Smelled what was very similar to stale air coming out of a tire if you bleed it off after overfilling.
Then smoke coming from pass footwell.
Pulled over and we pulled the cover. #16 fuse (cooling fan) was scorched at the ends w insulation melted slightly. The “fuse” (center portion) was actually still intact. We ended up pulling it as it was cool enough to run w viscous fan for the remainder of the trip.
(Temp never want higher than 1/2 way)

Sounds exactly like the above info in the thread.
i took the CE panel apart about 12 yrs ago, cleaned panel and replaced all fuses/relays.
The electric fan doesn’t seem to have any resistance and certainly not locked up. I’ll have to explore the fuse Block and make sure no damage there.
Will try new fuse, clean contacts and squeeze them together. Hopefully that’ll do it.
Thx!