1028 gen 1 light problems

[ranchhopper]

I have a 1028 thats giving me fits trying to solve the gen 1 light going on with the heater fan. I have checked the voltage both batteries have a full charge even with driving this truck around for a month now the batteries have the correct volts when checked with the truck shut off and the 14 volts when running. The trucks oil pressure light never did come on when the key is turned on and the only time the gen 1 light comes on is when the heater is turned on and the light shines very brightly when its on and the heater motor does not turn. The gen 1 light has never come on when the key is turned to the on position just like the oil pressure light the fan motor is not siezed either it turns by hand freely and runs fast and quietly when useing a jumper wire from the 12 volt junction block to the motor as a test. I took the gen 1 down to the local rebuilder he tested it and it put out 14.2 volts so it seems this is still good the gen 2 light comes on at start up it always has since I got the truck a little bump in the RPM and it goes off like it should. The voltage gauge goes right up into the green as it should when the gen 2 light goes out the gauge never moves when the heater is turned on and the gen 1 light comes on when the ignition is turned on the only light that lights up is the gen 2 light I have been reading and rereading the threads that turn up under a search but cant seem to find a cause for this problem.

 

[dependable]

Would guess that the diodes or rectifier in gen 1 are on the way out. You could have bulbs out as well. One other possibility is that the heater motor resistor (mounted on firewall with 2 screws behind back battery) is shorted or rusted to ground.

 

[ranchhopper]

The guy at the shop is familiar wiith these generators and said it was OK and the gen 1 light does light up at turning the fan control on but I will check the fan motor resistor anything I can do to shorten the list of possibilitys will work.

 

[dependable]

Most of the time, the gen 1 light coming on with fan motor is a failing alternator diode. It may charge, but not at 14+volts and not at lower RPMs. Rebuilding or replacing the alternator usually cures it. The fan motor resistor was a problem I had once.

 

[cpf240]

I've also heard that the blower motor switch can be a cause of issues with the GEN 1 light coming on when the blower is turned on. I bought a new one from cucvelectric, but have yet to install it.

I like the idea of the blower motor resistor though!

 

[ranchhopper]

But would these suggestions cause an open circuit causing the gen light not to light up when turning the ignition on?

 

[dependable]

I would guess that the problem is in the alternator.

 

[ralbelt]

My Gen 1 light would not come on when key was turned to on.. After checking voltage readings, checking and changing bulbs, rebuilding Gen 1 and having it tested, I found that the groung wire from Gen1 ground stud to the engine was corroded internally and not giving a good ground although the ends were clean. Replaced it with a new wire and Gen 1 light came on at turn of key and off at start up ,voltage guage reading in the middle of green.

 

[ranchhopper]

I would guess that the problem is in the alternator.

I had the alternator checked today they said it was putting out 14.2 volts.

 

[Jeremiah_Johnson]

I had a similar problem on my M1009 and it was a blown fuse (heater fuse ) I think, in the fuse block . Seams like the heater and the exciter for the gen is on same circuit.

 

[ranchhopper]

I had a similar problem on my M1009 and it was a blown fuse (heater fuse ) I think, in the fuse block . Seams like the heater and the exciter for the gen is on same circuit.

The fuse is good thats the first thing I checked.

 

[ranchhopper]

My Gen 1 light would not come on when key was turned to on.. After checking voltage readings, checking and changing bulbs, rebuilding Gen 1 and having it tested, I found that the groung wire from Gen1 ground stud to the engine was corroded internally and not giving a good ground although the ends were clean. Replaced it with a new wire and Gen 1 light came on at turn of key and off at start up ,voltage guage reading in the middle of green.

The ground wire looks good but I will make a new one tomorrow at this point I will try anything that might help.

 

[Warthog]

Change the ground wire and also remove/unhook the heater switch from the dash as a test.

The wiring diagrams don't show it but the GEN1 exciter circuit and the heater motor share the same fuse. Diagram E-20 in the -34 TM

You might also check the Blower Motor Resistor on the fan housing.

If the switch IS bad then it might be causing the exciter circuit to not work properly. And since you say the fan works but not with the switch, that points to a bad switch.

One other thought, sometimes the noise suppersor at the fan will go bad. Might remove it also.

 

[ranchhopper]

Change the ground wire and also remove/unhook the heater switch from the dash as a test.

The wiring diagrams don't show it but the GEN1 exciter circuit and the heater motor share the same fuse. Diagram E-20 in the -34 TM

You might also check the Blower Motor Resistor on the fan housing.

If the switch IS bad then it might be causing the exciter circuit to not work properly. And since you say the fan works but not with the switch, that points to a bad switch.

One other thought, sometimes the noise suppersor at the fan will go bad. Might remove it also.

Swapped out the resistor no difference tryed a used switch no different but it was not the best switch so Im going to buy a new switch tomorrow and try it.

 

[MarcusOReallyus]

Jumper across the switch. That will tell you if it's bad without spending any money.

 

[ranchhopper]

Jumper across the switch. That will tell you if it's bad without spending any money.

Good idea I will give it a try.