Skip to main content ↑ ↓
Topic: Dash heat blowing cold, '03 U320 (Read 789 times) previous topic - next topic

Dash heat blowing cold, '03 U320

Steve and I got a call earlier today from a member who has the same year/model coach as us - his dash heat is not working.  The blower is putting out air, just not heated air.  He's left it running quite long enough for any lag due to the long run of coolant hose to be seeing heated engine coolant.

There's no valve to turn in that year/AquaHot coach, confirmed by his call to James Triana.  I didn't catch all of the info, but James suggested it could be a valve related to the dash climate control up under the dash area/possibly visible behind the genset. 

Any first-hand wisdom of this problem on the forum?  Our member is headed to cold climates due to an illness in the family so he doesn't have the luxury of stopping for too long to work on the problem.  He's running the AquaHot but additional engine-provided dash heat would be nice.

Thanks guys (and gals)!

Michelle
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Dash heat blowing cold, '03 U320

Reply #1 –
Most ( if not all ) Dash AC/Heat systems will have a water control valve to regulate the heater core temps.  It is probably near the heater core in front.  This valve will most likely be vacuum operated so a loose or missing hose or a cracked plastic fitting would not let water control valve open. A quick check is to see if heater controls will switch air flow from Defrost to floor heat if not then you have a problem with vacuum, may be bad vacuum pump or simply a kinked or broken vacuum hose.
 It may also be cable operated with same problems. As best you can follow heater hoses from engine feeling for heat, if hose goes cold at some point there will be a restriction.
Does this coach have the cutoff valve in the water bay the directs all water flow to heater core in winter instead of thru motor aid in water heater ?  If so it should be closed in winter.

Gary B

Re: Dash heat blowing cold, '03 U320

Reply #2 –
Quote from: Gary Bouland –

Does this coach have the cutoff valve in the water bay the directs all water flow to heater core in winter instead of thru motor aid in water heater ? 

Gary,

My understanding from the phone call with JT is that our '03 U320's do not have this valve.  Steve and I couldn't recall ever seeing one, either.

Thanks for the other detail!  I searched the archive and couldn't find any info - your explanation will help others like me who aren't familiar with some of the vehicle system concepts.

Michelle
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Dash heat blowing cold, '03 U320

Reply #3 –
I had the same symptom on our 2000 U320 and became convinced that the valve up near the front of the generator on the passenger side was not working as it would turn easily by hand but the knob on the dash had no effect.  I asked the guys at FOT to check it  when it was in for service and it took them about 10 minutes to find a broken wire.  Unlike most automotive systems that use a cable or vacuum line, this one uses an electric servo motor.  If this one is the same, the function of the valve can be checked by taking the servo motor off and turning the shaft by hand.  I was anticipating the purchase of a new servo and was pleasantly surprised with only a small bill for soldering a connection.
Monti
2015 Born Free Triumph Royal 4x4
Previous:  2000 U320 3600

Re: Dash heat blowing cold, '03 U320

Reply #4 –
Quote from: Michelle –
........................He's left it running quite long enough for any lag due to the long run of coolant hose to be seeing heated engine coolant...................................
Michelle,
But did he leave it running long enough for the engine to come up onto the engine thermostat?  Was the engine temperature up to normal driving temperature?
If he's testing for dash heat by running the coach sitting at rest vs. driving, the engine may not be up to operating temperature, with the thermostat open, which has to happen before engine heated coolant gets ciculated forward to the dash.
On the '98's, the dash temperature control valve is located immediately beside and slightly above the gen set opening, curbside.  It's degree of opening/shut is cable positioned by the heater temperature control knob.
Neal
The selected media item is not currently available.
Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten

Re: Dash heat blowing cold, '03 U320

Reply #5 –
Two engine rubber heater hoses run up the center bay ceiling and come out on left or right of generator as the hoses go up through the floor to the dash heater core. Visible from generator area will be a valve that controls coolant flow in hoses.

Michelle, take a look at your coach to see if you can find the valve and pass on where it is located.

Movement of dash heater control should cause the valve to move. When valve is closed hot coolant will no flow to heater core and hoses should feel very warm indicating hot coolant flowing inside hoses. Hoses are about 3/4" in diameter, sometimes orange/red or black in color.

Is this something that has changed and used to work ok?

Or is this an Aqua Hot issue?

Re: Dash heat blowing cold, '03 U320

Reply #6 –
I would not think this would be an aqua hot condition, but rather as previously stated the heater control valve.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins
 

Re: Dash heat blowing cold, '03 U320

Reply #7 –
Quote from: Neal Pillsbury –
But did he leave it running long enough for the engine to come up onto the engine thermostat?  Was the engine temperature up to normal driving temperature?

Neal,

Yes - Steve spoke with him and they had been driving for a couple of hours. 

Quote from: red tractor –
I would not think this would be an aqua hot condition, but rather as previously stated the heater control valve.

That's my understanding - just trying quite remotely to help him identify it if possible.  Our coach is in storage right now so it's not as easy to try and find this as we'd like.

I really appreciate the help, folks!

Michelle
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320