Voltage gauge cycling when i first start truck

[banjobob]

I bought a brand new battery and alterntor and it helped for a bit but the other day it started acting up again kills the battery to the point that the truck stops running. after disconnecting the relays to the intake heater it works fine agan. could my computer be taking a dump?

[PToombs]

The relays could be stuck on. Use a test light and see when you have power on the big terminal to the heaters. Check with key off, then after it has been running and is warm. If it is the computer, worst case wire a switch in the cab to turn them on.

[banjobob]

It is not sticking on i dont think because it does cycle its when it does kick on it goes way down then comes back to normal on my gauge it will cycle a few times before it quits running. should it not draw power the whole time if a relay is stuck on?

[dazedandconfused]

What year is your truck? Sounds like the voltage regulator is getting weak and dieing. It may be time to wire up an external regulator if yours is in the pcm.

[PToombs]

When you 1st start the truck, it's normal for the grids to keep heating for several cycles as the engine warms up. It's normal for the volts gauge to drop way down to 10 or so as this is going on. If the battery keeps going dead you may have another problem, either a draw you're not aware of, or it's not charging correctly. Put a volt meter of some kind on the battery and see how many volts it's charging. Then turn on the lights, fan, wipers and such and check it again. If it's not charging a little over 14 volts you need to find the bad part, if it is, you need to find the draw. Easy way to check is to remove the ground terminal from the battery and put a test light between the post and the ground terminal. It may flare and then go out, this is normal. If the light stays on, you have a draw, a light on like the glovebox light, dome light, radio. Or a short in a circuit. The wire to the dome lights runs under the drivers floor mat and wears thru sometimes causing a short.