Bounder: 94 Bounder - Engine Heat is weak

[BillNorman]

So one of my punch list items on the 1994 Bounder 34j is figuring out why the dash vents put out such poor heat while in motion. If the RV is parked with the engine running, they'll put out heat just fine. Blower motor is strong. All selectors regarding a/c, defrost, re-circulation, dash vents seem to be working properly. But going down the road, the heat is barely perceptible. Coolant is filled to appropriate levels, and once again - it's no issue if the bus is parked with the engine running - the heat coming out of the vents is much warmer.

Any ideas?

[planojeeper]

Could be a plugged heater core.

[BillNorman]

I considered that, but I'm confused why it would put out heat while at rest, but run cool at speed? I'm not talking about a general air differential at speed - I mean the actual air blowing out of the vents is cooler when moving down the road than in a parked position. I had a friend suggest that perhaps a weak vacuum line somewhere could be responsible, but that is officially going over my head when it comes to automotive know-how

[bobandshaz]

Thermostat is bad engine will be hotter setting still moving down the road air will help to cool the engine.

[planojeeper]

Water pump will move coolant slower at idle and will allow some flow into the heater core. When you are driving the water pump moves water faster so if the heater core is plugged you wont get any coolant into the heater core. bobandshaz that could also be the problem too. It couldnt hurt to change the thermostat just to see if thats the problem they are very cheap and easy to do yourself. the heater core is not so easy or cheap.

[BillNorman]

A little googling failed me - any hints on where the thermostat is on a 1994 454?

[stink]

Originally Posted by BillNorman

A little googling failed me - any hints on where the thermostat is on a 1994 454?

follow the upper rad hose from radiator to top of engine, the tstat is under the hose adaptor and just remove hose, remove two bolts(watch the ground wires under the rt bolt) and remove housing. clean old gaskit and intall new tstat just as the old one came out. A defective check valve to the vacuum reservware for the hvac system may cause similar symptoms, as you drive the manifold vacuum drops and the heater valve then partially closes or the blend door moves to the cool position.
another note, does your temp guage read normal? if so then there might not be anything wrong with the tstat

[Gary RVRoamer]

If it heats well when standing, the chances are that air flow is the problem rather than heater core. Probably the outside air inlets are open, letting cold air mix with the heated air and chilling it. The HVAC system has "doors" that are supposed to close off outside air, either automatically based on the control setting, or manually (the "recirculate" or "max" control position). Many systems close the outside door automatically when Heat is selected.

The doors are often operated by air pressure (vacuum), either directly or via a lever arm of some sort.

[House Husband]

Bill, I have a 95 Bounder with the same Denso HVAC system as yours. I crossed southern Colorado in January at -7F with plenty of heat with the system set for out side air. So out side air is not the problem. Your HVAC system is all electric with NO vacuum controls. It doesn't have a water control valve but uses a servo controlled blend air door to control the temperature. 3 possibilities are malfunctioning blend air door, engine thermostat, or restricted heater core.
Richard

[BillNorman]

Engine thermostat seem to be good - if the temp gauge is to be believed. It seems to be performing as one would expect. I think I'm going to attempt to blow out the heater core tomorrow.

RLS, thank you for your input. Can I ask - how has your Bounder held up to Winter camping? Have you used it with the plumbing system wet and unwinterized in true Winter conditions? Have you taken any special considerations with the plumbing in regard to tank heaters, etc? I realize this is a bit of a thread-jack, but given what you posted it seems like you may have some valuable information for me... we will be boondocking in serious Winter conditions in a few weeks, and it would be helpful to heat from someone with a very similar rig.

[House Husband]

Originally Posted by BillNorman

RLS, thank you for your input. Can I ask - how has your Bounder held up to Winter camping? Have you used it with the plumbing system wet and unwinterized in true Winter conditions? Have you taken any special considerations with the plumbing in regard to tank heaters, etc? I realize this is a bit of a thread-jack, but given what you posted it seems like you may have some valuable information for me... we will be boondocking in serious Winter conditions in a few weeks, and it would be helpful to heat from someone with a very similar rig.

Bill, Our ol Bounder does well in the cold unwinterized. The furnace supplies all the wet bays with heat. BUT Fleetwood screwed up the return air in the wet bays. Spending a night at 0º would allow the water pump to freeze. I redid both the supply and return air in the wet bays and now my Bounder will tolerate more cold than I will. GRIN
I will note that there was a major design change in 95 and my storage bays are quite different from yours. I have remote thermometers in the wet bays so I can monitor the temperatures. You might consider the same. That way you'll know when to turn on the heating lamps.

Richard

[BillNorman]

From what I could tell, the vents into my wet bays were passive - ie: they allowed air exchange between the wet bays and heated areas of the RV, but there was no forced air component to it.

Today I installed 12v computer fans to access holes to force heated air down to the wet bays. They are switched, and I also added one of those nifty thermostats that has two remote send units so that I can monitor how things are going down there.

We also got the new flat panel mounted today Unfortunately, I didn't get around to diagnosing the heater core issue - that's on the agenda for tomorrow.

Thanks for your replies and support!

[LSC9901]

Did you find any resolution to the heat issue ???? Inquiring minds want to know.

[bobandshaz]

Originally Posted by LSC9901

Did you find any resolution to the heat issue ???? Inquiring minds want to know.

Me too