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

TX76513 · #1 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.

tangofox007 · #2 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 · #3 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?

kerry · #4 09-01-2010, 02:47 PM

Quote:

Originally Posted by grindMARC

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?

No. Alternators don't typically overheat and die. You need to do some testing. Test the battery and test the alternator for output.

TX76513 · #5 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.