This is a problem I have been dealing with off and on for months.

Problem: Charging system sits at 15.5 volts, even at idle.

Attempts at resolution: Tried 3 different verified working alternators, bypassed ECU using standalone external regulator, disabled all add-on electrical accessories, ran larger cable from alternator to battery, tried 2 other verified working external regulators. Tried 2 other verified working batteries. Removed battery from system completely.

Change: None

My van has reverse Midas touch when it comes to charging system components. Every component works fine in any vehicle besides mine.

I cannot figure for the life of me what could be causing this. Bad ground somewhere? Open circuit? Van made from metal taken from Indian burial ground? Blowback from ouija board usage? Benjamin Franklin's ghost?

Oh, and yes, the voltage reading was taken at the alternator stud, battery, and the factory voltmeter agrees.

 

I think we have a batter temp sensor...I think it could be that (if we have one)

 

You have an bonding jumper between the vehicle body and engine block that is conducting insufficiently, if at all.

 

External regulator's metal bodies must be well grounded, or full fielding of the alternator and overcharging will result.

Grounding out of either of the field wires will cause the same result.

But I like the Indian burial ground theory more and would go with that

 

The external regulator's body is grounded to the body, and in addition, has 2 10 gauge wires grounding it directly to the battery.

Grounding out of one of the field wires may be a winner, because I found today that the alternator will charge with only one of the field wires connected. Once the field wire that brings ignition power is connected, then it really goes wild.

Going to check all connections, and try again.

I will also check the jumpers too. One was completely missing, and I just replaced it.

 

Resolution: Aftermarket tensioner contacting the ignition coil, wearing through the case, exposing engine components to ignition voltage. Replaced tensioner and coil. No more issues.

 

wow -- good find...those type of problems can be unnerving and never found

 

You're telling me. I've been such a klutz concerning vehicle repair, I amazed myself.