Alternator problem for M1009

[Mattgyver]

Ok so i have an 85 m1009 and both alternators went out after a long trip. I bought replacement alternators on ebay eBay Motors: M1008, M1009, M1028 CUCV ALTERNATOR 12V 1105500 OE 100A (item 160200848047 end time May-14-09 11:11:26 PDT)


My mechanic who is a diesel specialist says he can only use one because the second one needs to be internaly grounded but im pretty sure i bought the exact same alternators as before... Anyone got anything on this?

 

[m38inmaine]

From the factory both are isolated ground, this way you can switch them around and not worry. Also simplifies the supply system. Not sure why he would say that unless someone has messed with the wiring.

 

[Mattgyver]

so i just called him back and he says that these alternators are not isolated but maybe hes wrong. Im pretty sure they are the right ones since they are made for my truck (according to the ebay add) .. he says hes worried if he hooks them up they will short out or fry the battery... Maybe i should just take the truck home and throw em in myself and see what happens. what do you think?

 

[ralbelt]

The passanger side must be an isolated ground, only the drivers side can be a case ground, the military used both being isolated ground to simplify inventory.If you are not positive about the isolated ground don't install them you could cause yourself some real problems.
If you use the search feature and type in isolated ground you will find a wealth of info on this subject, thats what I do most nights trying to learn this system.

 

[Crash_AF]

The easiest way to check this is to go from the ground stud to the case with a ohmmeter. If it is anything but infinite ohms, it's not an isolated ground. If they are both isolated grounds, tell him to install them.

Later,
Joe

 

[davo727]

Both alternators are the same then?

 

[ida34]

Yes. Unless they have been changed by someone else but from the military they are both isolated ground 100 amp alts. The same on both sides.