Red flashing lights on the N3207 regulator on our 10/02, M1078A1, ss#A-T018674EFKM


New member
Have been using the 500 series Troubleshooting Guide for the N1511 Alternator.

The batteries are running 12vdc – 12.1 and the 24vdc – 24.8

The voltage on the 28V post for the regulator has 14 vdc

Everything is check for good connection and clean grounds

Tried checking the light on the LBCD but could not see a light

Read about adding more batteries to the 24 vdc side and that would Excite the alternator. I tried that by adding a battery charger to the 24 Vdc side with setting of 24v 15 amps. Shortly after that voltage can up on the 28v of the alternator. Regulator light turned amber that the green. After about one hour that 28v side of the alternator had reached 28.4. At that point I turned off the battery charger and shortly after that the red flashing lights came back on the regulator. Yes, that voltage came down on the alternator. Next day I repeated this with a charge of the 24 vdc batteries.

New day 24 batteries 26.2

12 battery 12.4

Started truck up with a quick crank of the Cat. (hot batteries)

Regulator flashing red lights 24 vdc at 28v post

Same red light on regulator until I added the 24v battery charger. Then shortly after voltage comes up green light on regulator.

When I turn battery charge off voltage goes down and red lights flashing comes on.

Suggestion or better solutions Please


Well-known member
Supporting Vendor
If you remove the lead from the front regulator terminal it should measure 24v. You cant measure it connected you get voltage feeding back thru the regulator. If you dont have around 24v at the lead, run a temporary wire from the batt 24v to the regulator front terminal see if the alt excites and starts making power.


Well-known member
Port angeles wa
The excite voltage superman is talking about is only present when the engine is running/has more than 15PSI of oil pressure. It comes from the de-energized contacts of relay K11, so K11 must be a 5 pin relay...

Your battery voltages don’t sound right. The 12 should be almost exactly 1/2 of the 24v. So the 12-24 batts are 13.8 and the 0-12 batts are 12.4?

disconnect the batts, measure them individually and charge and load test them individually. I suspect you have a bad battery in the 0-12 half(the batts furthest from the frame) and the alternator does not work correctly with imbalanced banks.

flashing red = overvoltage. Basically the alt is trying to charge a bad 12v batt and feeding as much current that way as possible. this alt design only has one excitation coil for both 12 and 24 though, so in trying to push up the 12 with a bad battery, it is driving the 24(with good charged batts) into over-voltage...

if both inner batts closest to the frame are the same at 13.8, you can remove both outer batteries, and move one of the inner batts to the outside position and tie it in there and see if the alternator performs correctly with 1 good inner(12-24) and outer(0-12) battery...
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