2nd Gen Non-Engine/Transmission Poor cab heat

[Fish On]

Wise TDR members please help. Truck is a 1996. I have poor heat in the cab unless I put the heat selection switch on recirculate. In recir mode it will cook you out but the windows start to fog up. Switch to defrost and the heat is only pee warm. Any ideas. Thank you for your time and input.

 

[GAmes]

Try pulling the fan assy out and I think you will find one of three things. 1. Shine a light in there and see if the heater coil is plugged up with dirt, pet hair, leaves, what ever. Might need to be removed and cleaned. 2. Feel around and see if it is leaking coolant (do you smell antifreeze when in recir?) Obviously that will require replacement, which is the same amount of work as removing and cleaning. Or 3. the fan itself may be full of debris and/or not spinning at the right speeds. Easy fix. Since your windows are fogging up I believe #2 is the problem.

 

[Missouri Mule]

It could be that the the heater core can not over come the cold air coming in the vent. Covering part of the radiator mite help out when vent is open.

Even in the mild temps here in central Florida my windows fog up at night if I have the heat/vent open and not using defrost but then again my the temp stays the same ( in the Freightliner with the Mule if the t-stat opens up in cold weather my temp drops and goes back up when the temp gauge hits 180).

 

[SMorneau]

What is the outside temp when this happens? Heating system in my truck sucks as well but once the engine temp stabilizes it will keep the window defrosted in all but the coldest weather (note Minnesota location). Recirculate is the only effective setting even if I had to vent a side window. I used to wear snow bibs on my 50 mile drive to work and it was difficult to keep the cab warm if traffic would slow to a crawl. I never used it but I did carry my generator and an electric heater cause I figured if I ever got an ice storm followed by a real cold blast I would not be able to clear the windshield with an idling engine and would do it with the electric heater at least to get going.

At least no one made me drive for lunch in the cold weather.

 

[LHastings]

Fish I have the same problem as you do. I just replaced my thermostat this weekend from cummins they said i was a 195. When I drove it to work this morning it made no difference ( outside air 26 deg f). I check the heater for leaks and debris and did not find any. Here where I live I can't just block off part of the radiator because one day it can be snowing and the next day we're in the 80's.

 

[SSolderitch]

I got better heat when I replaced the boots & elbows on the plastic 1/8" vacuum line & the larger line comming from the vacuum pump. Most say it is the connection behind the turbo were it goes thru the firewall, but mine was the tee (more like a F) by the master cylinder at the hood seal.

 

[LHastings]

SSolderitch On my 98 the temperature control is cable driven and the outside/inside air damper is vacuum driven and both of those dampers are okay.