Possible Grid Heater Problem?
 

The last couple of days when I start my truck I notice the voltage gauge doesen't cycle (charge/discharge) when the grid heater is cycling. It sticks down around 10 volts or so. The lights still dim/brighten but the gauge just doesn't show it. It used to bounce back and forth like they all do. My question is....could the grid be malfunctioning or am I looking at a charging issue. Once the cycle quits the lights brighten back up and the needle shows a charge. Any help is appreciated. When I get off work in the morning I'll start looking at it....just haven't had time since Friday.

Possibly the relay for the grid going south? This really bugs me....I hate electrical problems.

If the lights are dimming the grid is pulling voltage.
Maybe the gauge is going bad?

Just verified the grid is operable as well as the relays. I'm leaning more towards a charging issue now. Talked to a local starter/alternator rebuild shop and he said "well, just bring it by and we can check it and make sure it's charging properly"!!!!! ARE YOU FREAKING KIDDING ME!!!

The lights dim/brighten with the grid cycle so I know the heater and alternator must be functioning properly.....the "gauge" shows a little over 14v charge after the heater is finished cycling so I know it's charging at some point. Could there be an "exciter" of some sort built into the alternator to help it build a charge faster at idle? I know my dads old Cat front-end loader won't show a charge until the engine rpm's come up considerably which is why I have that thought. I know the ECM controls most of what the alternator does but there has to be a simple issue I'm overlooking here.

I'm not sure. I know my gauge fluctuates with the grid even when cold. It sits at about 10 when I first turn the key, and if my compressors are running I hear them bog down as the heater grid kicks in, then when I start the truck the voltage gauge reads 14.5 until the grid cycles and it drops, then goes right back up again.

Yep...that's what mine has done for almost 9 yrs now up until 2 days ago!! I almost think it has to be something in the alternator for it to not show any kind of charge at all until the grid is finished doing its' thing. Struck me as really odd that it's no longer reading charge/discharge while heater is cycling. What's even got me more baffled is the fact that it shows a "good" charge after the heater is done. Even with the grid disconnected at the relay it shows a "discharge" for quite a while and then........CHARGE just like normal [duhhh]. I'm kinda lost on this deal to tell ya the truth.

I guess my last resort is to just take the dang off and have it checked huh?

After a couple of hours of tinkering with it yesterday I did find that the grid is functioning, the alt does charge after a couple of mins being "stuck" down around 10v or so, and the lights dim/brighten with the grid cycle. What kinda has me stumped a little is that when I disconnected the cables from the grid relay and started the engine the gauge still dropped back and stuck at 10v but I could still hear the relay clicking.

Did a little searching this morning and found that some folks were having similar symptoms and come to find out the grid relays were stuck open and allowing a huge draw on the charging system....so much that the gauge would hang way back because the alt couldn't put out enough charge to satisfy the system.

If that were to be my problem, would the interior lights still dim/brighten with a stuck relay? I also read that bad batt cables could be an issue as well. My cables and ends are clean, however, the negative ends on both sets leave a lot to be desired as they are just on the verge of disentigration....maybe thats my problem.

Alternator is up to snuff so I can rule that gizmo out of the equation.

There are 2 heaters and 2 relays. It sounds as though one relay is sticking closed and the other is cycling as it should. I would locate the relays and disconnect them one at a time from the circuit and see what happens.

2 relays huh? Never thought about 2 of them. Yesterday afternoon the weather was warm enough for the grid to not run (yeah I know...Feb. and warm weather) and as soon as the truck started...boom...full charge!! It almost has to be a faulty part in the grid/relay system.