Gen 2 stops flashing when heater's on

[rpellicci21]

My Generator 2 light flashes when the engine goes any higher than an idle, but I found that stops when I turn the heater on. Does this just mean that the alternator is overcharging because there is little to no load on it but when the blower motor comes on gives it a load?? My main concern is there a way to adjust this so the alternator is not always overcharging besides driving with the heater on. Does it do any damage to the alternator or battery if it is constantly being overcharged? I read up about the adjusting the fast and cold idle screw but I don't know if that would have any effect because the problem is when the truck isn't idling. Thank you for any insight.

 

[Ken_86gt]

Overcharging the battery will ruin it. I suspect that the regulator or rectifier inside the alternator has failed. The only way to know for sure is to start testing. The use of the heater should not make any difference to Gen2 as it is on the Gen1 circuit. Maybe a bad ground or loose connection contributing to this - again you will have to start testing. I am assuming that you have not looked in the TM and followed any of the troubleshooting guides?

 

[rpellicci21]

Thanks for your response. I did some basic testing before and everything checked out. With the truck off there was 12 v to the driver side alternator, 24 to the passenger side alternator. The batteries both checked out. I looked at the TMs and the regulator is supposed to be set to high so even if it is overcharging I shouldn't lower it right? If that is the case should I just replace it? Thanks

 

[rpellicci21]

Oh I forgot the mention that the alternator I am having problems with was missing the alternator wiring harness, or the exciter plug, when I got the truck. I ordered a new one and connected it by braiding the wires together then covering it with heat shrink wrap tubing. I was wondering if this had something to do with it because that is part of the regulator I think? My other thought is because the wire was cut and the harness was missing maybe it was removed for a reason. Maybe they were getting to the problem and dropped it? Maybe a bad rectifier like you said.

 

[Ken_86gt]

You can't adjust the regulator, only replace. Check the voltage while the engine is running across the + and - battery terminals and not from the +24v to ground. This test does not check for bad diodes, but is still useful. Check the voltages at idle and when the light is on and report back the results. At this point I am not sure why you think it is overcharging, it could be undercharging.

 

[rpellicci21]

You might be right. I haven't seen anything in the TMs about the the meaning of gen 1 and 2 light flashing not solid. Or does it always supposed to flash when there is a problem? I was thinking it was overcharging because the GEN 2 light only flashes when the engine goes anything higher than an idle. I was thinking maybe the engine was spinning the alternator too fast causing it to overcharge for whatever reason. The other thing that led me to believe it was overcharging was the fact that with my foot on the gas and and the GEN 2 light flashing I could directly control the GEN 2 light by turning the fan on and off leading me to think that the overcharging was being compensated for by the blower motor drawing a load from the systems. But you said it is on the GEN 1 circuit and should have nothing to do with GEN 2 which throws another wrench into things haha. And with the regulator I was just going out of the TMs it showed a adjustment screw on the alternator regulator. And part of the troubleshooting was ensure the adjustment screw on the voltage regulator was set to HI.

 

[rpellicci21]

Could those symptoms I described be due to undercharging as well?? Thanks again for you help Ken

 

[cpf240]

My understanding of how the GEN lights work is that they light up whenever there is a voltage difference between the batteries and the alt output. When the key is on, but the engine is off, current flows through the batteries to light the bulb. When the engine is running and the alternators are working, there is a balance between the alts and the batteries, though there is probably a small difference but not enough to see the bulbs light.

If the alts are not working, then it is the same situation as when it is key on, engine off. If the alts are overcharging, then the difference is great enough to make the light from the bulbs visible.

I'm sure I'm not explaining it well, but that is my basic understanding of those lights, and that also could explain why they can't easily be replaced with LED bulbs, as the LED bulbs generally only allow current flow in one direction.

As mentioned before, the heater blower share the fuse for GEN 1, so it is not uncommon for the GEN 1 light to come on with the use of the heater blower when things are all in spec. I have no idea why the GEN 2 light would be affected by the heater blower.

In any case, a meter is needed to test what is actually going on.

 

[rpellicci21]

Thanks, you actually explained it really well. So is there different meanings for when the GEN light is solid as compared to flashing?

 

[cpf240]

Thanks, you actually explained it really well. So is there different meanings for when the GEN light is solid as compared to flashing?

It all comes down to alt output and loads on them. Those are just lights, there are no smarts in them. The smarts comes from the operator with the meter.