Engine/Transmission (1998.5 - 2002) voltage/amperage fluctuation??

[merryman]

Yesterday when starting my '01 HO 6speed, it cranked a half-second before firing, so I put a volt meter on (when not running) and got only 12. 51 volts.

Today I took it to a battery shop and when they had their machine hooked up and engine ideling(after a 55 mile drive), it would be showing about 14+ volts (it moved around a little), and about 50 amps; then suddenly and for about a second, the volts would drop to around 12. 3 and the amps would jump to around 150 amps. then back to as it was before for a few seconds then back again.

The heater was on, so I turned that off thinking maybe it was the air cond. condensor cycling, and it seemed to quit. Later it seemed to do that change with or without the heater or defrost running. Then for a while it did not ???

One battery had a bad cell so we installed two new batteries and the situation repeated as before.



The temperature was in the low 60s and it was a damp day with intermitant rain.



Ideas?

Could this be the air intake heaters cycling? and if so could the cool day with several minutes of ideling let the engine cool enough to cause that , even though I had driven 55 miles at highway speeds?

Is it more likly a defective AIT sensor??

Something else??



I would appreciate ideas------other than go to the dealer.



Thanks



Vaughn

 

[Steve Campbell]

My guess is...

the grid heaters!!!



It is amazing how short a period of time my truck has to sit in these temps, before it cools off enough to ask the grid heaters to cycle at start-up.

 

[CrewCabDiesel]

Heck,

My grid heaters will cycle after shutting down the engine to place an order in the Mcdees drive thru. My 91 also did the same thing, I would think the sensor that sets it off is reading out side air temp, not engine temp, but thats just a guess.

Kyle

 

[andrewkoperdak]

The grid heater comes on at approx 60 degrees F. Mine cycles on and off for several minutes if the air is around 60. My voltmeter heads for 10 volts and then comes back rapidly and then the next cycle starts. Sounds like this is what you are experiencing?