Tow truck jump box COOKED my alternator - PeachParts Mercedes-Benz Forum

grindMARC · #1 08-31-2010, 07:26 PM

I left the lights on. I should have called Mercedes Roadside Assistance -- mistake #2. I called Allstate instead. Then sent out some Russian dude who left the jump box hooked up for about 90 seconds. I should have caught this... mistake #3. On the way home, the radio starts cutting out. The gauges started acting crazy and then all the electronics were dead. I get home and try to restart the car -- NOTHING. I mean NOTHING. I had to hook it up to a battery charger just so I could put the windows back up!

My alternator is about 18 mons old. And its toast now.

The only good part about today is the homebrew that I'm drinking as I type.

SirNik84 · #2 08-31-2010, 07:44 PM

Just my $0.02

I got my SD because my dad was tired of replacing alternators. I drove the car and replaced 2 alternators before the problem was found. The radio was always the first to go, then the gages, then everything else! I took the car back to the shop that changed out the alternators for my dad. When the problem was finally solved it turned out to be the diode. $0.50 part killing $100 alternators

grindMARC · #3 08-31-2010, 09:24 PM

Quote:

Originally Posted by SirNik84

Just my $0.02

I got my SD because my dad was tired of replacing alternators. I drove the car and replaced 2 alternators before the problem was found. The radio was always the first to go, then the gages, then everything else! I took the car back to the shop that changed out the alternators for my dad. When the problem was finally solved it turned out to be the diode. $0.50 part killing $100 alternators

More accurately, I think that was your 50 cents -- not 2 cents.

tangofox007 · #4 08-31-2010, 10:49 PM

Quote:

Originally Posted by SirNik84

When the problem was finally solved it turned out to be the diode.

Could you elaborate on "the" diode?

vstech · #5 08-31-2010, 11:09 PM

I see no way a "jump box" could have fried anything, more likely the alt was already failing, and this is the reason for your needing a jump in the first place. plan on replacing the battery, and the alternator, and drive safely!

JHZR2 · #6 09-01-2010, 02:06 AM

+1 to everything VS said. Often one leaves jumpers connected to the battery so that it can recharge a bit prior to trying to jumpstart. Staying on like that should not have caused anything.

JHZR2 · #7 09-01-2010, 02:07 AM

Quote:

Originally Posted by tangofox007

Could you elaborate on "the" diode?

Yeah, please do. The diode is in the alternator, right? So I dont see how one diode would kill multiple alternators... If a diode was bad, shouldnt it have been swapped when the alternator was?

Or is this a situation of an external voltage regulator, perhaps where the diode is in that box and not necessarily replaced with the alternator????

TX76513 · #8 09-01-2010, 08:55 AM

Quote:

Originally Posted by tangofox007

Could you elaborate on "the" diode?

It's usually the backout diode that goes. Most alternators will have 4 -6 diodes in them. If you ever turn your car off, remove the key and the ALT idiot light is on dim? It's the backout diode. Radio Shack part for a buck or so.

JHZR2 · #9 09-01-2010, 10:19 AM

But isnt that part of the alternator? The person above made the mention that they went through multiple...

I'd think that replacing one would get you a different diode and the issue wouldnt be replicated...

moon161 · #10 09-01-2010, 10:52 AM

Quote:

Originally Posted by JHZR2

Yeah, please do. The diode is in the alternator, right? So I dont see how one diode would kill multiple alternators...

Saw the wanted poster at Autozoo- dead or alive, for serial alternator sabotage.

tangofox007 · #11 09-01-2010, 11:14 AM

Quote:

Originally Posted by TX76513

It's usually the backout diode that goes.

Can you show us a "backout diode" on an electrical schematic? When I Googled the term, the only thing that came up verbatim was a comment in another forum. The comment was left by none other than TX76513. Apparently, you are the only person who knows what a "backout diode" is!!!

Quote:

Originally Posted by TX76513

Most alternators will have 4 -6 diodes in them.

Can you provide an example of a specific automotive alternator with only 4 or 5 diodes?

grindMARC · #12 09-01-2010, 11:22 AM

So after reading these replies and doing a bit more research, my latest theory is that since the electronics on car were slowly dieing, the battery was not accepting any charge that the alternator was providing. And over the course of my 30 mile trip, the alternator overheated and died.

Does this seem logical?

TX76513 · #13 09-01-2010, 01:22 PM

[QUOTE=tangofox007;2536508]Can you show us a "backout diode" on an electrical schematic? When I Googled the term, the only thing that came up verbatim was a comment in another forum. The comment was left by none other than TX76513. Apparently, you are the only person who knows what a "backout diode" is!!!

Probably not the only person. Try Schottky diode. Most people use backout probably because nobody know how to pronounce Schottky. Very common in solar pannels now, marked on the schematic and or diode with an arrow to show the direction of voltage flow (voltage Clamp). This diode is part of a diode pack (trio) in an alternator.
Place one of the ohm meter leads on the single connector on the Trio (Touch the other lead to each of the other three connectors, one at a time. The meter needle should either show continuity or no continuity, but should be the same for each of the three connectors. Now reverse the ohm meter leads and do the test again. The meter reading should now be reverse of the reading achieved on the first test (if the needle “pegged” on the first test, it should do nothing with the leads reversed). All three connectors should be the same. This test verifies that current can only flow in one direction, and the same direction, through all three of the diode connectors. If any of these readings is not correct, the Diode Trio is bad.

SirNik84 · #14 09-01-2010, 01:32 PM

Its on the back of the alternator, its back, and about 3/4" square. thats the part the tech tossed at me and said "this is whats been killing the alternators" I have in it in my glove box, kind of a "good luck charm" I suppose.

tangofox007 · #15 09-01-2010, 01:46 PM

Quote:

Originally Posted by SirNik84

Its on the back of the alternator, its back, and about 3/4" square. thats the part the tech tossed at me and said "this is whats been killing the alternators" I have in it in my glove box, kind of a "good luck charm" I suppose.

Then it's definitely not a diode. Capacitor, most probably. A new alternator typically does not have the noise suppression capacitor installed, so the old one gets installed on the new alternator.