Hello all. I hope I'm not repeating any previous threads; I've had a look and don't see anything similar to my problem. I had an erratic rev counter with the needle either not working or bouncing. From what I've read this is usually an alternator problem. The truck was running fine so I just left it until I started having more issues. I then replaced the alternator cause it is a quick part to change and the old one was definitely looking like an original part. I had about 11.5 volts between the battery terminals with the engine shut off but the voltage would drop to ~10v when running. The new alternator does the same thing so obviously I don't have a problem there. Any ideas? I'm not sure where to "start" here (sorry, bad pun).

 

The battery should be no less than 12.6VDC with motor off, running should be 14.2 +/- .2 VDC. I'd have the battery checked for a dead cell. Your readings indicate the battery is about to go kaput. Hope you saved your original alternator..... you can rebuild it (bearings, diodes/rectifier) yourself and it will far outlast any parts palace rebuilds. Probably wasn't bad to begin with......

 

I was assuming the initial low battery voltage was due to it not having had a proper charge, but it would be awesome if it was as simple as a bad battery. It's not that old but who knows?

 

I would have the battery checked. If it is the battery charge the new one to 100% before installing/using.

 

have you checked the 100amp fuse?

 

Yep the 100a fuse is good

 

A shorted battery cell will draw down the running voltage.

 

I will have to get it looked at by the local mechanic. I have just a basic dmm that won't tell me much about the battery.
Will come back with the results!