Battery not charging. What am I missing?

[71monacomoparmechanic]

my battery on my 71 monaco is not charging. Changed the alternator with tuff stuff 130 amp and tuff stuff voltage regulator. Still not charging. Checked continuity of the two field wires to the alternator to voltage regulator wires are good. Swapped batteries and ko positive result. Grounds are good. What else is there?

 

[Davea Lux]

Run a voltage check on the lead going to the output on the alternator, you should have battery voltage there. If not the circuit is open someplace and the cause needs to be determined. The 130 amp alternator is too big for the factory wiring to handle, it may have toasted the circuit to the battery. The are several threads on this site about upgrading the alternator circuit to handle the increased output from a high amp charging conversion. Also be sure that the voltage regulator has a good ground as it will not function without one.

Dave

 

[71monacomoparmechanic]

I have battery voltage there at the power output cable on the alternator. The guy at summit racing said I will have no issues with the higher output alternator. It did the same thing with the old 60 amp anyway and did not charge. The car has a bigger than stock alternator wire going to a junction at the starter because it has a trunk mounted battery and also uses msd distributor and ignition not that it's very relevant to the concern.

 

[71monacomoparmechanic]

I will have to verify ground at the regulator at this point.

 

[Big_John]

Here's how you test it.

Take a voltage reading at the battery just for reference, car not running.

Disconnect the green wire from the alternator and make a jumper wire that goes from the connector on the alternator to a good ground.

Turn on the headlights on high beam and start the car.

Check the voltage at the battery again. It should be 14-15 volts at minimum. If it's not, there's a problem with the alternator. If there is, the problem is either the voltage regulator or the wiring to the VR.

Don't run the car for long like this. Just long enough to check voltage.

This duplicates the FSM procedure except you are using the headlights to load the battery rather than the carbon pile. What we are doing is bypassing the VR to perform the test. The VR controls the alternator by completing the circuit in the field by grounding it.

Don't have a FSM? MyMopar - Mopar Forums & Information - Service Manuals Might have to download the Plymouth version though. It will be close enough.

 

[3175375]

^^^ What @Big_John said. By doing this, you are commanding the alternator (via the jumper) to “Full output”...

 

[71monacomoparmechanic]

Thank you all very much. I will test it tomorrow and post what I find.

 

[71monacomoparmechanic]

Looks like the voltage regulator had a bad ground.
Ran a redundant ground from the v reg to the engine and it works.
Thanks to all for the info