1083a1p2 no charge light

[Mpkasper]

I have 3 trucks that all have the same problem going on with them. The mileage flashes, the no charge light comes on, the 24v gauge sits at 0 and the oil pressure gauge sits at 0.

the 12v gauge also sits low but if I put the truck in gear it will jump up to 14v and the no charge light will go off. Everything will still not work though. One truck I got to come back to acting normal after reading on here to disconnect the ctis harness but it could just of been a fluke.

just about everything charging wise has been replaced. Fresh batteries, alternator and regulator, load bank, and mmdc have been swapped with a known good.

has anyone found a fix or had this problem before?

 

[Ronmar]

On the A0 trucks and early A1 trucks its the 15PSI oil switch That controls alt. on the A1s they altered the circuit slightly so that the same relay(K11) first enables the starter, then disables the starter after oil pressure is sensed and enables the alternator. The neutral circuit also joins in and when you come out of neutral, it remofes the power supply from relay K11 which will act as a secondary control to disable starter and enable alt.

On the later A1 trucks with the bussed/integrated gauges and MMDC, which it sounds like you have, they switched from oil pressure control to MMDC control. But they kept the neutral relay interaction. You seeing it jump to 14v when you come out of neutral says K26 and K11 are working normally to enable the alternator. When the engine ECU reports RPM above ~350 to the MMDC, it energizes relay K40 in PDM3 which removes the ground path for K11 de-energizing it and shifting it from start enable to alt enable. You could check K40 and make sure it has a good coil and will energize when power is applied…

if you have 14V you must have 28V, the charge failure light going out also confirms 28v as that is what the LBCD measures along with RPM to determine if it is going to light that dash light or not. So that along with no oil pressure and no start disable/alt enable would point me towards a bad gauge control module(MMDC) or a communications issue with the engine ECU, or you have some bad bussed gauges…

Good luck…

 

[Suprman]

Theres a grouped ground under the power panel thats been knows to cause issues

 

[jwchameleoncorp]

I had the same thing going on in one of my trucks. I swapped the CTIS module with another truck and it fixed the problem. The other truck started having the same issues so it was pretty clear the problem was cause by the CTIS controller. I replaced it and everything worked properly again.

Sent from my SM-N986U1 using Tapatalk