I need your help. I have a 2006 2500 Ram and having trouble with my cummings. We are located in nebraska and its cold. My pickup will not heat up but going down the road it may go up to 190 then down to 140 then when i stop its below that. I had a new theromstate and clutch fan put on it and it didnt help . Also my tach is reading almost nothing at idle..Could this be my ecm, does it need to be flashed.
Secondly, only one thread is needed for this subject. I moved your first one to the proper section. Then I deleted the second one you just posted.
Lastly, I don't think the tach reading has any bearing on your heat problem. I believe you have a heater core problem. It may be plugged and not letting the heat transfer to complete the cycle.
The puzzling thing is the weird fluctuation in temp while in motion. I would think that it would rise when you come to a stop or are at idle, then lower as you move down the road, moving more air through the radiator.
How new is your coolant? And have you had the system flushed recently?
I just went through this situation about 2 weeks ago. Being fat, dumb, and happy and with the temperatures on the cold side, I have not checked my fluids lately. About a week ago, I noticed the heater was not producing heat as it normally does. I did notice that the heat output would change with engine rpm. The higher the rpm the more heat. I made a mental note to check the fluids. by the way, mine is a gasser.
On the way home, I noticed a sweet sicking smell, anti-freeze. Ah crap. Hoping it was not the heater core, I got home and started to look for the cause the violated my senses. Interior cab nor wet, no moisture from the vents. Opened the hood and said yes.
Water pump, no. Hoses, no. Coolant reserve tank, low. looked under the vehicle, wet. Radiator side tank gasket went south.
New radiator purchased, flushed the heater core, and 2 hours later, back in business.
hubble - there's a chance you have air in the cooling hoses, which would cause the problems you've described. I just changed the heater core and heater hoses in our '96 and to get the air out I would leave the radiator cap loose, start the engine and let it run until the thermostat is open, and then squeeze the bottom hose (being sure to stay clear of the fan). I then tighten the cap and squeeze the hose again.
With the engine fully warmed up and running, have you squeezed the two hoses going to and from the heater core? They should both be very hot, and be at about the same temperature.
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