canadakonrad

suddenly the voltage gauge dropped down. doesnt charge. bad contact? alternator is fine! pcm? batteries? cant figur it out! thx

Spooler

Sounds like the grid heaters are on. If they are, it is normal. If they are not, you may have a bad battery.

HOBrian

X2! If this is happening when you first start the truck than it is the grid heaters turning on.

Sevir

whats your voltage gauge doing? the stock one on the dash has a horrible delay on it from the ECM. I can put a volt meter on my alternator/batteries and watch them come up to 14.2VDC and 30-40 seconds later my gauge on the dash will finally catch up. If its a sparatic change, then you might have a problem. Put a volt meter on your batteries and watch what they do real time.

canadakonrad

well i had my batteries tested today, they are completely fine. nothng wrong. had the altenator tested. its working properly. i put everything back together and it was working fine for a while. then after i drove off, the voltage gauge drops down. at first slowly then almost all the way down. im lost.

canadakonrad

also what is a grid heater? sorry.

notw

The grid heater is located in the air intake. It preheats the air prior to entering the engine. It was brought up because the heater pulls mega amps and will drop your volt gauge reading considerably during the cycles. This is all normal and controlled by the computer sensing the incoming air temp.

canadakonrad

ok ill check that. where does the voltage gauge messure the volts of off?

Sevir

your ECM, where you ECM gets it would be a guess

JHardwick

This has been posted about for 7 years now. If you hook up a DVM, you will see the grid cycle. If you watch the factory gauge you will only see a low voltage condition, which is controlled by the ECM.

randallp84

I think you need a little clarification. Nobody has clearly explained the grid heater voltage drop. The grid heater cycles on and off when the outside temperature is under a specific setpoint. So when it's cold outside and your grid heater is cycling, you will see your voltage gauge drop when it comes on. It will stay on for a few seconds and then turn off. Then you will see your voltage gauge jump back up. It will stay off for a few seconds and then come back on and you will see your gauge drop again. This will occur until your engine warms up or until you get above 20mph.

If your voltage gauge is dropping and staying low, then it is not your grid heater and you have a problem.

Sevir

it might be just the 04.5, but my voltage gauge doesnt move when my grid heater cycles. i can watch my head lights and interior lights dim and brighten, but the voltage gauge doesnt move. As i said earlier there is a 30-40 second delay on my dash gauge. But this might be a 04.5 issue.

JHardwick

This is not true on either of my '03s. They both drop below 14v while the grid is cycling, and then return to 14v+ after the grid has finished it's cycle.

randallp84

Interesting. I have an 04.5 and I instantly see the voltage drop and increase when the grid heater cycles.

canadakonrad

ok, i got it fixed. it was my alternator afterall. last time i checked it it was working good, then it quit. running fine now. thanks guys