Hello, I have been GROSSLY misdiagnosing my engine fault code so I have attached a YouTube clip incase I'm making another mistake.

http://www.youtube.com/watch?v=E99SlRtLY2g

I believe that I have codes...

12 - Battery or computer recently disconnected (yup, I understand this one)

41 - Alternator field control circuit open or shorted

55 - End of codes (yup, I understand this one too)

My 1990 B250 318 5.2L starts fine, appears to charge fine, and runs fine. I have owned the van for over 3 years with the same battery and I have not had any apparent problems with the electrical system.

I read in another post, regarding the alternator, that the field coil in the alternator could be bad.

Quoted from 11-12-2010, 01:57 AM
1994 RAM B250 stalls when coming to stop,

"The alternator field is a coil inside the alternator that is controlled by the voltage regulator to (ahem) regulate the voltage output of the alternator. - Alloro"

Can this coil easily be replaced, do I just need a new alternator, any thoughts on where I should start?

Thanks for your time in advance.
roberson

ps - the quotation was to help in taking note of what previous posts I've scoured.

 

I don't know of any place to buy just the coil. Because of that you're stuck buying another alternator. But this code doesn't necessarily mean the problem is within the alternator. The problem could be with the circuit running to the alternator field coil, or it could be a bad PCM since the regulator is built into it. Bring the alternator in to be tested, most auto parts stores will do this.