My RV's Dashboard Heater Is Not Blowing Hot Air

by Howard Nelson
(Thousand Oaks, Calif.)

I have a 2004 Discovery on a Freightliner chassis. It has a 330 Cat diesel engine. The dashboard heater will blow a very, very little bit of warm (not hot) air, but not enough to keep you warm on a cold day.

I have had it to Freightliner and other RV repair shops with no luck at all. Could it be a heater control valve? If so, where would it be located and how big of a job would it be to replace? This has gone on now for over 2 years and I can't find any help anywhere.

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Any assistance through you or any readers that may have had a similar problem would be greatly appreciated.

Thank You.


ANSWER: Hi Howard the first thing we need to establish is that this is a common complaint among owners of larger Motorhomes and that in most cases the dash heater on any motorized RV will not provide enough heat to heat up the whole RV on a cold day. The same thing holds true for the dash air conditioner on hot days. The bigger the RV the bigger the problem of not heating or cooling the whole RV with a dash heater or AC.

That being said, I still think you have a problem since you are only getting slightly warm air through the dash heater. The problem could be a bad Heater Control Valve (sorry but I do not know the exact location of the valve on your RV).

The problem could also be caused by a malfunctioning heater blend door that is not sealing properly, a blocked or partially blocked heater core, a partially blocked hose leading to or from the heater core, or even low engine coolant level.

Again, without being able to physically look at all of the components I mentioned above, I cannot tell you for sure what is causing the problems. One thing you can do is look at the documentation you got from the repair shops that you have taken your RV to; to see if they also looked at everything I mentioned.

Hope this helps.

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Comments for My RV's Dashboard Heater Is Not Blowing Hot Air

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Cool heater
by: Noshow1961

Check under your motorhome Cat has 3 shutoff valves for the water to the heater core 1 on the side of the engine above the water filter and 2 under the coach along the frame rail on my 07 Bounder the first one is behind the power block for the shore power and the other is beside the muffler hope this helps good luck

by: Lewis

I had this same problem and have the same motor home with the same engine.Pull both lines from the heater core and back flush in to a clear plastic bottle.I will bet you will see chunks come out of the heater core just like I did and my motorhome only has 10000 miles on it.I went from cold air to so hot I have to turn the heat down.

Dash Heater troubleshooting
by: Howard1

Try a search for Evans TEMPCON Imc. They have a very good troubleshooting guide complete with vacuum diagrams and detailed instructions. Hope this helps!

RV dash heater blowing warm but not hot on cold days
by: KirkofPlantEarth-beammeup-Scotty sounds like folks could improve the heating, when that is the case, by changing the thermostat to a 195, instead of the 180...of course we'd want to change back to a 180
((or my preference, 160)) in summertime, so the engine can run winter, the 195 thermostat will help the dashboard heater air achieve a little warmer warm, on the coldest days...

Same Problem
by: Discovery Owner

I have the same problem with my 2000 Discovery and so do most other Discovery Owners. I belong to the Discovery Owners Association International (DOAI) and on the DOAI Yahoo eGroup this is a common problem with both Cummins and Cat engines in motorhomes. To my knowledge no one has found a solution to this problem. My explanation is that the engine thermostat opens at about 180 deg and my Cummins runs at about 183 deg on a cold day and does not get much warmer except when under load like climbing a hill and as the engine temp increases so does the heater output. The heater core is located at the front of the coach and it is a long run for the heater hoses. My thought is that there is a lot of cooling on the exposed heater hoses before the coolant reaches the heater core.

heater control valve problems
by: Kirk-beammeupScotty

What about the possibility of an Engine Thermostat that is stuck in the open, it might allow warming of the radiator fluid //enough to heat via the heater, at idle// but proceeding down the road on a cold day, would cool the engine coolant in the raditor so much //with the thermostat OPEN// that it would barely allow any warm water for heating.....smells like a stuck thermostat to me....

Now if I could just find a 4 port heater control valve for my 91 Cruisemaster (georgia boy/ford/28ft) motorhome, I could switch from heat to ac again....

Kirkout (beam me up Scotty)

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