proudpapa97

Hey guys I have a '97 twelve valve and I am currently on a trip in route to California. Last night when I pulled off the road and get some gas, I noticed that at
idle speed all the lights (interior and exterior), as well as the gagues were dimming and then coming back on.(Almost like a voltage regulator problem/surging tendancy)


Once back up to highway speed they were okay when the amp gague was reading 14.
Maybe the battery or the alternator?

Any feedback would be appreciated since I need to deal with this before it gets dark.

Many thanks,
Steve

labreck

how old are the batteries? typicly they will last 2 years. also the fuel heater sometime (i hear on this forum) will cyicle on and off with a bad silinoid. a parts house can test batt. and alt. so you can rule those out. good luck.

johnh

sounds like this "
It's time to "sticky" this one at the top of the forums again.

If this describes what you're experiencing when lighting off the Cummins on these frosty mornings,.......
Don't worry, it's normal.

The Cummins uses a pair of 12 volt grid heaters in the intake tract
(imagine two large toaster elements glowing bright red)
that preheat incoming air for easier combustion.
The Ford & Chevy use glow plugs inside the combustion chamber.
As the relay cycles the grids on & off, the large amp draw causes the volt meter reading to drop, and the lights to dim when the relay turns on the juice.
The relay timer will turn off the heaters when the intake temps hit a preset limit, or when the vehicle exceeds a preset MPH (usually between 15-25 mph). edit


Don't panic "

proudpapa97

Johnh,
Thanks for the info. Would this still be a problem that would occur once the truck is warmed up?? I had the problem after I had already been driving well over 4 hours that night.

The truck performed fine on the way home though and made it back.
Thanks for any info you can provide.
Regards,
Steve

torquefan

Yep, it may start doing it after you slow down, depending on the ambient and intake air temperatures. It should stop over about 18 mph.