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Topic: Dash heat question (Read 1083 times) previous topic - next topic

Dash heat question

When I got my coach the dash heater would not work. I could turn the switch to dash or defrost and the air flow would switch to the correct location but when I switched the switch to heater/floor the air would continue to come out the dash. Also the air would not get hot so I assume there is a switch somewhere allowing the hot water to circulate thru the heater core. Today I replaced the vacuum generator behind the step with an electric pump. On a check of things now the dash air will switch to all 3 locations, dash,floor or defrost, so apparently the leaking vacuum generator was not pulling enough vacuum to work everything properly. My question is is there a vacuum operated control valve on the heater water lines that possibly might work now that there is enough vacuum?? I did not have enough time today when I hooked up the vacuum pump to run the big motor long enough to get the water hot to see if I had dash heat. It would be great if it does it would be one more little thing marked off my to do list.......
The selected media item is not currently available.Keith & Jo
2003 U320T 4025 PBBS Designer series
Build 6203    Cummins 500hp
2000 U320 4010 WTFE / Build 5762 —Sold—
Motorcade #18070   
Pasadena, Texas
2015 Jeep Wrangler Sahara-Sunset Orange pearl coat
Don't argue with a fool, people watching might not be able to tell the difference.

Re: Dash heat question

Reply #1 –
I have about the same problem, mine switches between dash, def, and floor but I get no heat or cold air  :o
Steve

1997 U270 36' build 5179
Motorcade #18147
1980 CJ5

Re: Dash heat question

Reply #2 –
If you have a motor aid domestic hot water heater you may have to close a valve to divert engine water to the dash heating coil.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Dash heat question

Reply #3 –
Don't know how the newer coaches work, but I think on our GV, the water control valve is mechanical.  I've never actually seen the valve, but that's how it "feels" to me.  We do have the motor aid water heater, and the bypass valve at the water heater is always "open".  Even so, our dash heater will cook a pot roast on the full hot setting.  I actually have a hard time reducing the temperature to a comfortable (for us) level.  I have to keep pushing the temp lever in the "cooler" direction until (it feels like) I just barely have the water control valve open.  At that point, the air coming out the vents is warm, but not scalding hot.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Dash heat question

Reply #4 –
On our 95 it's a cable operated valve located next to the dash AC evaporator.
Shaped like a "H" with 4 coolant lines running to and from it.
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Dash heat question

Reply #5 –
So, IF the water control valve is indeed still mechanical (in the newer coaches), then vacuum "power" may only be used to position the air flow control "doors".  This is the way many auto and truck heaters operated in the "old days".

Run your fan on high speed and try all the air flow positions (dash, dash+floor, floor, and defrost) to see if the air comes out the proper outlet.  If it does, then your vacuum (or possibly electric) flapper motors are functioning properly.

With the big engine running and at operating temp, if you don't get dash heat when the heater temp control is moved to "HOT", then the water control valve must be inoperative, or the mechanical control cable (if there is one) disconnected.

Further speculation/investigation/info:

Ford HVAC control on dash.

Heater "H" Valve

2000 U320 Dash Heater Blower Replacement Part# 26-19904

99' U270 Heater core replacement Saga.

Technical resource:  Evans Tempcon > Owners Resources
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Dash heat question

Reply #6 –
I believe in my 02 the valve is electric. If you lift the front Gennie door it will be on the upper left side under the windshield. Mine hasn't worked since I bought it.. haven't really looked at it yet but I will in the future..

Re: Dash heat question

Reply #7 –
My 2000 320 heater valve stopped working and then began leaking so I changed it out. The valve I replaced was an Eaton 354-69494. I replaced it with a valve from TruckAC.com, 625-4314. It is in the approximate location described earlier. Simply follow your heater hoses up into that area. Not all that difficult to change out and it's great to have that dash heat to keep your feet and legs warm.

The valve is electric.

Cheers!
Bob
Bob & Suzy
2000 U320 4010 SPEC
2006 Honda CRV