Pehaps this has been covered, but it has me concerned. I am a 1 month old CTD owner and it seems odd to me. Vehicle in question is an 06. Last night after work I fired up the truck to go home. Temp was 40. I immediately turned on the heater fan and just sat in the truck for about 5 minutes to let it warm. About every 20-30 seconds the fan speed would slow and the volt meter would fluctuate. Volts would be running at about 15 and the fan would be blowing hard. Then the volts would drop way down and the fan speed would slow. Then both volts and fan would go back up. It just kept going thru this cycle. I thought it had to do with the truck being cold, but after pumping gas last night I fired back up and it did the same thing. At this time the truck was at operating temp. It has me a little concerned as I am about to take off on a hunting trip. Oh, and idle speed during this cycling never changed. Also with High Idle turned on, the volts and fan speed flucuation still ocurred. Do I have a problem???

Thanks,

 

Not sure if it's the same but my dads rv has an isc330 and it does the same thing, found out that it was the intake heater cycling.

 

just as jakebrake said. It is your intake air heater grids energizing. They draw a fair amount and will duplicate the exact symptoms you describe. I am pretty sure the heaters come on at 45 degrees and below. They superheat the intake air to aid in combustion.

It's normal. If you have access to an outdoor receptacle, get yourself an nice, heavy gauge extension cord. 14 gauge or bigger will be fine. Plug your truck in when it gets cold.


Also, my truck will activate the heater sequence even after it has been at operating temp for some time. Same application as you. At a gas station or anyplace where the truck is off for only a few minutes. I am not sure if it's an air temp sensor that kicks the heaters on, or some sort of timed circuit. Either way, it's normal.

Good luck.