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gperryrv · 02-06-2011, 09:25 PM

I have a National Tradewinds that sits on a freightliner chassis with 3126 diesel motor. The dash heater is not working. The guy I bought it from said it could be the heater valve is shut off but he didn't know where it is. Does anyone know where the valve is located or any possible areas to look? Thanks in advance.

srydve · 02-06-2011, 10:27 PM

I have a Newmar but it is on a freightliner chassis and dash heat problems are common. If you do a search on Evans control valve you will get lots of info. I replaced mine and it cured my problems.

gperryrv · 02-07-2011, 06:09 AM

Thank you for the reply. I will search this today and let you know the results. Thanks again.

Lault · 02-07-2011, 07:25 AM

I also have a 06 Tradewinds and the dash heater core was leaking. The AC condenser and the heater core are one unit at a cost of $350.00. So I do not have dash heat due to the replacement cost of $800.00 for replacement and labor. Never heard of a heater core and AC condenser being combined.

Vintage · 02-07-2011, 06:48 PM

It is probably on the firewall on the passenger side where the hoses enter the air exchange box. It should have a control cable going to it.

If this is open you might check the inline water valve in the heater hose on the drivers side alongside the frame near the middle of the engine.

bigdog · 02-11-2011, 08:12 PM

I have an '01 7390 LTC and the heat will blow for awhile and then kinda goes away and then a bit later it seems to heat up again.Wonder what causes that.

Vintage · 02-11-2011, 08:23 PM

Is the fan blowing all the time? If the fan is blowing does the heat go on and off. Is the air flow cycling between going to the defrost area and then to the floor? Need more info.

gperryrv · 02-15-2011, 08:28 PM

It was the valve that was turned off. All set now. Thanks for all the replies.

Vintage · 02-15-2011, 08:45 PM

Quote:

Originally Posted by gperryrv

It was the valve that was turned off. All set now. Thanks for all the replies.

Which valve? Your answer could help others in the future.

HeapBigEngin · 02-15-2011, 10:58 PM

Yes....I would also like to know which valve was turned off.

Not sure about Evans control valves. If it was one of the valves (coolant outlet/coolant inlet back at the engine) that feeds the front heater system, I might toss out a word of caution. I was not getting dash heat in my F/Wood Revolution DP (Cummins/Freightliner). Found the outlet valve closed. Opened it and had immediate heat at the dash! Next day I found a puddle of coolant under the front of the MH. Eventually found bad hoses/connectors at the heater core inside the MH. Whew!! VERY happy it was not a heater core. I strongly suspect the previous owner had closed the outlet valve at the engine because he had discovered the leak....and did nothing about it. Seems that about the only reasons to close one or both of these valves is to allow better ac cooling performance from the coach's HVAC system in the summer....or to shut off a leak like mine. It is possible that someone might shut off the valves when changing engine coolant, thus isolating the coolant in the hoses and core up front, and then forget to reopen the valves. Suggest you make sure you DON'T have a coolant leak after re-opening the engine valve(s).

gperryrv · 02-16-2011, 10:30 AM

Update: It was the valve next to the motor. I checked all around to make sure there wasn't any leaks today. After reading your post I also called the mechanic that charged our air condition and he did confirm that he didn't open it back up after charging the air. Thanks again everyone for all the information to bring this problem to a close.

HeapBigEngin · 02-16-2011, 10:06 PM

Hey gperryrv....thanks for the quick info. Should be helpful to the folks that may be having similiar questions here. Also, very happy for you that your situation "fixed" itself....unlike mine. A lot of people seem to have to replace their MH's heater cores way too soon. Glad neither of us did! Take care....

Hooligan · 02-18-2011, 09:33 PM

2 years ago, On a walkaround at a rest area, I noticed a coolant leak at that heater mixer valve when we were returning from a trip. Rather than trying to fix it in the rain at the rest area, I closed the 2 faucet type valves at the engine, added a little coolant to the reservoir and continued home. Very convenient way to isolate that line.