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So I picked up my new 1999 2500 24v today :thumbsup:

Driving it home after about 20 minutes on the highway, I noticed the rev's were fluctuating down to 1700, back up to 1800, down to 1650, up to 1900, down to 1800 and then back to the normal 2000 all within a few seconds while keeping the foot steady on the gas pedal. What gives? :confused013: I'm pretty new to 24v engines, so any help would be appreciated. I also noticed that my dash lights were dimming and brightening back up intermittently. I remember reading an article about it, I just can't find that said article so info on that would also be appreciated.

Thanks a lot!
 

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Auto or manual? Is the vehicle speed changing also?? Is this at 70 MPH or so??
 

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well the dash lights dimming would make me think it's the grid heaters...but they ain't supposed to come on at that speed...

as for the tach fluctuation, that's normal, it's the ecu self checking itself or something like that...my 02 did it all the time
 

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If it's an auto, the converter is locking and unlocking due to electrical interference. A quick fix is to wrap the black/tan wire running from the alternator with heavy duty foil and go over it with electrical tape. Done well and with patience, it won't look bad and it should help stop it. Mine fluxuated when I first bought it. I wrapped the wire and haven't had a problem since. Gotta love free fixes! :D
 
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So do you think that could also be the case when pulling equipment? My auto. was recently "flashed" and my rpms are screaming around 2700-3000 and jumping from gear to gear. I just keep being told it is what it is. It wasnt like that before it was flashed and now it acts all messed up!
 

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Discussion Starter #6
well the dash lights dimming would make me think it's the grid heaters...but they ain't supposed to come on at that speed...
Sorry, I should have better explained myself. The lights were dimming while I was parked*. What is the usual fix for this grid heater problem?

If it's an auto, the converter is locking and unlocking due to electrical interference. A quick fix is to wrap the black/tan wire running from the alternator with heavy duty foil and go over it with electrical tape. Done well and with patience, it won't look bad and it should help stop it. Mine fluxuated when I first bought it. I wrapped the wire and haven't had a problem since. Gotta love free fixes! :D
Wow, I wasn't expecting it to be that simple of a fix! Thanks a lot:thumbsup:
 

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There is no fix for the grid heaters. While they run when the truck is cold they pull somewhere around 110 amps to operate. They run their cycle and shut of when you start driving at a certain speed or the motor reaches a specific temperature.

As far as the fluctuation, it could be the crank position sensor behind your IP going bad, that's where you get the rpm reading from I believe.
 

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now when the tach was fluctuating could you hear the engine doing the same thing?
if no then i would say the crank sensor which is hiding just behind the starter
 

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oh... is it the cam sensor behind the IP? That would make a lot more sense :doh:
 
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