2nd Gen Non-Engine/Transmission Cold Truck

[JR]

If the gauge is reading 140*, then it isn't the HVAC system or heater core. Even if the fan clutch was locked up the engine would still warm up. About all it could be is a bad t-stat.

This is true, but I believe he is dealing with 2 different problems. Even if the engine is making good heat if the compressor is not functioning correctly he will still be dealing with defrost issues.

 

[mwilson]

The a/c compressor does not run at those temperatures.

My Jetta has a thermistor that kills the a/c clutch at right about 32 degrees. GM uses 40 degrees ambient air temp as the cut off point.

I am away from my manuals right now but there is a specific temp on the Rams as well.

Mike.

 

[JR]

Mike I would be interested to see what you find. I know I have heard my compressor cycle in and out at temps below 30 degrees? I did a little searching through my book but did not find anything.

DGamelin, it may be worth your time to pop your stat out and double check it in a pan on the stove. If it tests fine and you have an old stat laying around I would gut it and put in in and start the truck to check for coolant flow. You should be able to see the coolant flowing in the radiator, if not, time to pull the water pump and check the condition of the blades. There isnt much else it could be.

 

[DGamelin]

I was Wunderding if the AC would work in thoes temps. Got it charged and it does cycle outside. The resin I replaced the thermostat because the truck didn't warm up. Two bad ones in a row, I guess. The old one got tossed. I was thinking about that water pump. I have been turning wrenches for over 30 years and never seen a bad pump make an engine run cold. Has anyone? The shop is backing up and I have runs to make, I can't keep farting around with this truck. I will pull the thermostat and the pump next week many even the heater core.

 

[JR]

I agree, a bad pump could cause poor heat by not sufficiently being able to circulate through the heater core, but not likely to make an engine run cold, unless your seeing false readings. Thats the reason for gutting the stat (if you remove it I dont know if the housing will seal?) and run the truck to see if the coolant is even circulating. That would tell you whether or not you even need to go after the water pump. You may well have a plugged heater core, but thats not the root of the problem, at least not yet.
Or if your pressed for time throw another thermostat at it (demand a 190) and worst case scenario you will have a spare.

 

[DGamelin]

Check part number with cummins they said it was a 190. They also said they have seen good water pumps cause poor heat. I am guessing the impeller is pressed on a little to far or the impeller was a little to short? I don't know. I am going to look at them both.

 

[DMcLeod]

My 01 had awesome heat originally (I remember driving across AK with a baby and the overhead console OAT pegged at -40F - as low as it goes). A few years ago, I began noticing a decrease in heater's ability to keep cab warm. I went through everything talked about on this thread, and eventually pulled the core. What I found was the old heater core flowed fine, but there was no heat transfer. I havn't cut the old core open yet (another story), but believe the coolant is bypassing the heat transfer fins/tubing. I tested this by placing both old and new cores outside at -15F. I then hooked each core inlet to my hot water outlet on my boiler (180F) and felt the core as it warmed up. The new copper core instantly got entirely hot to where I had to jerk my hands off. The old core stayed cold for a long time and did not get very hot in the center portion. Before, at -30f with heater on high, I had to wear arctic gear INSIDE the cab and scrape frost from inside while driving!!!!! I wish I could tell you how it's working now, but my dash is still dead after putting it back together. Instrument cluster is completely dead........but that's another story. BTW, my heater fan made it to about 170k miles before it sounded like a F16 one fine -45F day! Best of luck getting good heat DG.

 

[jdross440]

I lost heat when I put in a new core. The new one is aluminum. I couldn't find a copper one. Even the dealer's was aluminum now. Before you could keep the truck real warm on low or the next speed. I filled the core with 50/50 mix before connecting it to get most air out.