Blower overwork - PeachParts Mercedes-Benz Forum

JHZR2 · #1 07-25-2011, 02:11 PM

Im very familiar with the blower pulling too much current in w123s and causing a fuse to pop (or replacement with the strip fuse in the MB mod kit). Burned out a fusebox once...

This is different... was over 100 last saturday. Seems my 82's R12 charge is a little low (some bubbles in the sightglass). It was HOT. Had my AC set on auto for fan speed, and after being on a bit, I smelled what seemed to me to be burning electronics. Turned off or to low, no issue. Did this a few times and noticed it repeatedly.

Fast forward to Sunday, still hot, still lots of AC, just not AS hot. Run the fan on auto, its spinning fast, no smells. No nothing.

Any thoughts? I sure dont want an electrical fire. I got a fuse that Ill put inline at some point, but that can only do so much in one place...

Hopefully I dont have any issues. My car is running and looking so great right now, and will be even better when I get my chrome 15" bundts!

Thanks!

leathermang · #2 07-25-2011, 04:36 PM

I suggest you carry a CO 2 fire extinguisher inside your car...
not the dry chemical types...not the water type.... they both make HUGE messes....
Greg

JHZR2 · #3 07-25-2011, 05:12 PM

Yeah, Id hope to fix whatever the issue might be so that I never need to use one.

Saw the 300d fire thread... No thanks.

And an extinguisher is just to get out. Too many toxins in a car dash to fight it.

So how to fix or at least check out? Can I check resistance to ground on the conductors as a basis for condition?

leathermang · #4 07-25-2011, 05:29 PM

Electricity is my worst subject....
But if you had the CO2 handy I would sure shoot it under the dash AS I GOT OUT
and /OR held my breath..... it will cool in addition to taking away the oxygen from the fire...
I am just going for the bottom line last line of defense since you smelled what you did....
You could hook up the CO2 to a line directed up under the dash...hard installation... then you just pull the pin and run.... it empties the canister while you watch from safe distance... calling for help.....

JHZR2 · #5 07-25-2011, 05:43 PM

I sure hope to never have to use one.

I can pull the acc, see signs of heat, replace. I'm going to install a fuse for the blower... I can always reside with hi-temp automotive wire. I assume the blower is operated by a relay?

I'm not going to leave the solution to smelling overheated 30yo electronics or wire to be to carry CO2.

I think I can do a little better than that...

leathermang · #6 07-25-2011, 05:47 PM

I am just 'sayin'... as the last line of defense........ nice to have one... good insurance....

JHZR2 · #7 07-25-2011, 06:03 PM

Absolutely!

1980sd · #8 07-25-2011, 06:34 PM

I keep mine aimed at my crotch...

Diesel911 · #9 07-25-2011, 08:09 PM

Quote:

Originally Posted by 1980sd

I keep mine aimed at my crotch...

If CO2 is used to close to something it or they will freeze.

leathermang · #10 07-25-2011, 08:15 PM

I think that is where the expression ' blue _____ ' comes from....

Yak · #11 07-25-2011, 08:22 PM

If the current doesn't spike, the fuse (or strip) may not blow. If the motor was drawing heavy current the wires may have been heating and you were probably smelling cooking insulation. It's sort of predictable. The circuit and wiring were designed for what 8A? 16A? But that circuit now has a 30A strip fuse, so now the wires can carry more current than originally intended and they get hot.

I had a similar problem with a seized wiper motor in an Audi wagon. The motor wouldn't return to park due to a failed gear, but the current was steady and high. The fuse never blew, but the motor on the rear glass got too hot to touch and smelled horrible.

Assuming a clear cause-and-effect of motor on high for long periods = smell of burning, you've already done the easiest fix: don't run it on high for long periods of time.

To positively diagnose, you may need to hook up an ammeter in series with the fan motor. If the current goes up significantly as the motor runs for a while, then stays high until you select a slower speed then you know the motor is overheating.

Other fixes: replace the fan, improve conductivity into/out of the motor, reduce friction in the motor.

Maybe canned air to blow dust/dirt out of the bearings? Some form of lube on friction points?

JHZR2 · #12 07-25-2011, 10:51 PM

I dont have the strip fuse on this car, just the OE ceramic. Given that it did melt my fusebox in my 83, I do hope to do some/all of what was mentioned...

Yak · #13 07-26-2011, 07:03 PM

Quote:

Originally Posted by JHZR2

I dont have the strip fuse on this car, just the OE ceramic. Given that it did melt my fusebox in my 83, I do hope to do some/all of what was mentioned...

I'd start there and use some contact cleaner/emery paper or something and get the best connection across the fuse and the contacts. That may be a point of resistance in the circuit, similar to a partial blockage in a pipe to use a plumbing analogy.