Dean_Fuller

Had some time this Sunday to work on the problem. Swapped a few relays. Blower relay was the wrong number. Def relay was the wrong number but the window winder relay ( same part number as the other ) was correct. Swapped around some a few times and Charly ( another local 928 guy ) noticed the condenser fan was not running when the A/C was on. removed that relay and jumped it and I had A/C on every location, not just def....still the fan runs JUST on high which i am sure is the resistor Pack. BUT......Now the BLOWER relay gets VERY HOT. Will order some relays and see where that leads me. I did not see the fuse smoke but it was VERY HOT to touch. BTW the fuse is pulling about 13 to 14 amps....so it doesn't seem that would cause the excessive heat. Charly...if your out there and can add to this any...that would be great.

Plan now...a few new correct relays and then????

WallyP

The blower motor bearings may be dry or failing, causing high drag, thus higher than normal amperage draw.

The standard fuse and circuit should be able to run the blower with no heat problems.

Heat buildup may well be high resistance in the connectors. Cleaning all of the connectors in the relay base, fuse connections, etc., and then using something like Stabilant (Google is your friend) or Corrosion Block (Google again) might help.

Alan

Like I said at the beginning - replace these fuses and the fuseholders...

And describe for us exactly where all this smoke is coming from - the fuse itself or the wires? or the terminals ? - if its the fuse - its the same thing I've been telling you all along... suspend your disbelief... replace it all... buy good quallty fuses - cheap ones are poor quality materials... its the fuse to fuseholder connection that is usually suspect - not the wire to fuseholder connection...

Alan

blown 87

I have even seen supposedly best quality ones from Wurth be awful, but as has been said before, of the fuse melts before the link blows, you have a resistance problem.

Dean_Fuller

Update!

I replaced the fuse holder and fuse with a better one off the old panel after a good cleaning. No more smoke at fuse #17........but now the wire off the top of fuse #17 gets HOT to the touch close to the fuse and gets cooler the further you move down the wire. I also replaced a few relays.

So the resistance has moved from the fuse to the out wire close to the fuse. Where do I go now?

SharkSkin

Try to clean up that connection. The male terminal is easy to clean off, the female terminal you can clean by folding a piece of 220 sandpaper so it fits inside the terminal and scrubbing it. You could also tighten the crimp and maybe add some solder to it.

dcrasta

since you have two panels can you remove the suspect wire and replace it? could have corroded/damaged wire..
sounds like you are getting closer tho..

tmpusfugit

Dean, as Wally and mrmerlin have suggested I would think the problem is in the motor bearings themselves. I just pulled the fan assembly out of my '81 parts car and it is very hard to turn......I have not yet investigated if it can be saved by cleaning and re-lubing the bearings. When I get around to it I am going to try some "Nano-Oil".....after proper cleaning and the like...

oppps, old thread, please disregard....

Jim

Landseer

Time Flies, eh, Tempus Fugit?

tmpusfugit

That could be the understatement of the year.....

Alan

It is an old thread indeed.. however new ones on the same topic come up all the time...

NOBODY LISTENS.... ITS THE POOR TERMINAL CONNECTIONS AT THE FUSE.... now obviously its also at the wire/fuseholder coinnection - having solved the fuse one......

Why will noboby listen and all seem to want keep looking for other phantom issues without solving the obvious one first.

Yes maybe there are other issues too? - but how will you know till you solve this first - after all this is the most obvious symptom...!

I swear I will just stop bothering soon. Heat = resistance right there where the heat is - nowhere else....

Just right there where the heat is ....

Yes just right there where the heat is....

RIGHT THERE!!!

Its actually really obvious - why look elsewhere.....

If the end part of the wire gets hot - its either getting heated by the terminal - (most likely - so clean or replace the terminal) or it is corroded internaly (replace the wire - or part of it anyway).

Then move on to the other functional problems.

Alan

tmpusfugit

Alan, let’s just assume you are 100% correct, in that the problem is resistance in the wires and in the fuse contacts etc.

I have 2 928 ventillation fans right now. One of my fans unloaded draws about 6 amps on high and using 14 vdc, uncalibrated shop DC power supply. My other fan draws about 13 amps on the same power supply. Could one assume one of these fans might work well and the other could be problematic in the same car using the same circuitry? Ohm's law suggests that would be true.... fans have bearings that wear, collect moisture, and fail over time. Lubrication fails with heat, use, and time. And when bearings degenerate current requirements go up....considerably in the case of my current 928 ventillation fan motor.

I suspect you are very correct in that many or most of such problems are fuse contact contamination/oxidation/low contact pressure issues, as well as poor grounds and the like. However, there can be other causes. Over design current in a circuit will heat up the weakest (resistance) links....to your point.

Mrmerlin

what i have found is that the fans over time get dirty ,
the bushings on the shaft that is.
These bushings can be cleaned out with brake cleaner and compressed air
, clean the armature with a pencil eraser then lubricate the bronze bushings on the motor with some fresh electric motor oil this should reduce the amount of current that the fan will draw and also the amount of amps that the weakest power link must transfer, also it should prevent the resistor pack from ,overheating.
Note if the fan is still hard to turn after cleaning then you should probably replace it as the bushings are seizing

Alan

I'm not saying there can't be other issues that are contributory - what I am saying is if you have overheating fuses it is caused primarily by circuit resistance at the fuse connections and you should solve that problem first - ALWAYS.

If there is significant excess current (>~1.5x the fuse rating) the fuse will blow as intended. Up to well above that rating the fuse/wire connections should not be a source of significant localized heating.

Once you have solved any connection problems causing localized heating then you can figure out if you have other issues and their magnitude.

Until you do you won't even know what the total actual current or issues might be because the excess resistance will mask the true results anyway due to voltage drops and lower currents...
(unless you start testing components individually - and know what to look for)

Quite often this is the only issue - and yet causes other 'apparent' funtionality problems until it is solved.

Alan

tmpusfugit

I pulled the 13 amp fan, what a fun project, took it apart, cleaned the bearings as best I could, added in some light oil and followed it up with Nano Lube. The brushes were clean and the communtator also clean and bright. It is now running happily on the bench at about 2.2 amps current draw (no fan assembly, no shroud). I am thinking 2.2 amps is still high for absolutely no load, but I am going to clean the rest up and reassemble it and see what the current draw is in it's fully functional assembly. I do not have a good track record on "saving" these little "unserviceable" motors. I have not priced a new replacement, I most likely don't want to know....

And as I read this thread it appears as if Dean had already changed out the fuse/relay panel, cleaned the grounds, checked the wiring, and had the same problem. Hence my suspecting bad fan bearings, just like I had this week....and I had also followed your recommendations on all the above mentioned steps...