Started the car and the alt was squealing a little--
thought it was the belts.
Got about a block away from home and smoke started coming
out of the driver dash speaker grill!

got it back home and found some melted wires up under the dash coming
from the fusebox. Went to the JY and pulled the same wires to replace.
Haven't pulled my alternator yet.

So, could a bad alternator cause the wiring meltdown or
could a short in the wiring cause the alt to squeal?

Thanks,
Jeff

__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

I have not read of this happening to someone.

Best, guess is short in wiring or ignition switch; but it is a guess.

I had a wire come un-soldered from one of the buss bar in the Fuse Box but it cut off power to some items but did not short out.

But I have a W123.

__________________
84 300D, 82 Volvo 244Gl Diesel

Shorted wires will cause a large current draw. Spinning the alternator to generate a lot of current will cause it to be harder to turn. When an alternate belt is starting to get loose, you often hear its belt squeal for a few seconds right after starting the car, as that's when its replacing the energy that the starter just took out of the battery.

So, yes, it is possible that an unfused electrical short, which must be what happened since wires melted down, could cause the alternator belt to squeal.

The belt squealing wasn't the cause of the under-dash wires melting down, but its probably getting loose, so worth checking out when you figure why the wires melted.

__________________
'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

X2. Short increased load on alternator causing an already loose belt to squeal. I've heard of dry leaves around the AC blower resistor bank catching fire but that's on the other side of the bulkhead. What circuits use the wires you replaced? Are all the fuses good? None over rating or bridged?

Sixto
83 309SD

OK. Wires 13, 14 & 7 are melted.
I now suspect 7 is the culprit.
Number 7 had the wrong fuse in it: 25A fuse instead of a 16A!!
#7 controls the electric passenger mirror and I recently
replaced the shifter console with a nice one I found at the JY.
I will ditch the "new" mirror control switch and put my old one back in.

I'm going to replace all my fuses and make sure they are all the correct rating.
Lesson learned--make sure you have the right fuses installed!

Can a short like this damage the alternator?

Jeff

__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Jeff, The other posters have given you good answers...
the only way to know if YOUR alternator has been damaged is to test the output once you get everything back together.. or take it off and have it tested....
Even less than proper connections... ( it does not take an actual short ) can cause excess draw on the alternator.... corroded connections , corroded wires, etc...

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

If you're not already back on the road, I'd replace the fuses for the affected circuits one at a time if possible. As in drive a day or two with only fuse 7. If all is well, add fuse 13 and drive a couple more days. Then add fuse 14. This assumes you can drive safely without those circuits. That way if things go badly again you'll have a better idea where to look.

I don't think you can hurt an alternator by having too much electrical load. I'd be more concerned about the battery which has to make up the difference beyond the alternator's ability. What's the voltage with the key out (~12.8)? What's the voltage with the engine running (13.5-14)? If the battery warning light goes out when the engine starts and doesn't come on when you have the headlights and AC going it's probably fine. A dead battery one morning will tell you things are not fine

Sixto
83 300SD

There's usually only three reasons someone replaces a smaller fuse with a larger rated one: they didn't have a spare of the same rating, they added something to that circuit that draws more, or they were ignoring an intermittent short.

Unless there's something non-standard on that circuit, then the PO was probably ignoring an intermittent short that became, um.. not intermittent on you one day.

And yeah, switches do fail, causing smoked wiring. Happened on our Expedition last year.
Its possible, but probably not.

__________________
'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

A 25 A fuse in a 16 A circuit should not have melted wires if there was a short. The wires should have blown the 25 A fuse. Something else is going on. To figure out what, you'll need to study the wiring diagrams and do some tracing.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

If you haven't disconnected the battery please do so and do not connect it again until this problem is assessed and corrected.

Exactly which wires did you replace? What to they go to, terminate?

__________________
84 300SD
85 380SE
83 528e
95 318ic

Yes, had the battery disconnected immediately.
Worked on this most of the day today.
Attached the replacement wires to the bad wires and pulled them
into the cabin that way.
Heat shrink butt connectors and heat shrink tubing over that
to splice into good sections of wire.
Lots of inspection looking and feeling for anything wrong.
Back killer working under the dash for so long.

Fired the car up. No warning lights. But the windows weren't working.
Blown fuse #7. Also, the ice cube relays for the windows/seats seemed
very hot. Not sure if they get hot or not normally? Maybe fried during my meltdown?

#7 controls the passenger mirror.
I disconnected the console plug for the mirror and replaced all four ice cube relays.

Started the car and the windows worked fine.
Also the #7 fuse did not blow.
Stopped for the day and disconnected the battery.

I will be watching this carefully and getting my nose
up under the dash for the next few days.

Keeping my fingers crossed.

Jeff

__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

That used to be my thoughts too since the wires themselves should be able to carry more current than rated for at least a little while before the insulation starts melting, much less smoking.. until the headlight switch cooked some wires in our expedition. It didn't blow the fuse, wires were killed, and it was definitely the switch that failed (not the wires).

So yeah, the fuse should have blown, but it is possible for things to smoke without it.

__________________
'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

A photo of a damaged section of one of the wires.
It was smokin' in that cabin!
To answer Clemson's question:
#7 wipers, horn, passenger mirror
#13 hazard switch, locking system, seat adjust memory, clock and radio

Attached Thumbnails

 

__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Rooster, Good to see you the other day. Glad to hear you got her fixed.

__________________

Was driving down the road on Sat when I saw an SD with the hood up.
Turned out to be Sir Nik & Derek, who transplanted a 603 into his SD.
He had just pulled off the hwy suspecting a dropped valve
Hope it was something else. He worked really hard rebuilding that engine.

My car seems to be driving just fine so far.
Battery charging at 14

Jeff

__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end