[77newell]

By using a dual thermocouple temperature monitor I was able to learn a couple things about the dash heat in my 93 coach.

On a 40 degree outside temperature day the heater produced about a 40 degree rise when the blower was on low and a bout a 50 rise when on high. That was strange since if the heater core was limiting the heat those temperature rises would be reversed. It turns out that my air-rest vents are pulling air in and not pushing air out unless the fan for those is turned on high and then the output is pretty anemic. I'll have to tear into the heater box to find out how that is possible but it explains some of my limited dash heat. When I taped over those outlets, the temperature rose by another 10 degrees.

The other thing I learned is that the solenoid at the coolant boost pump is needed or the heat is always somewhat on. I had removed mine to determine if it was limiting my dash heat, it wasn't though it did allow the "vent" setting air to warm 10 degrees even with the lever on the heater control to be all the way to the cold side.

[Fulltiming]

Jon, if it is like my 92, there are three motors in the front panel of the passenger side front bay ahead of the generator blower. One of those feeds the arm rest vents. All three of mine were wired backwards, thus reversing the air flow. It sounds like at least one of yours is also wired in reverse resulting in the blower rotating the wrong direction. Some what of a pain to get to but easy enough to fix. After finding which one is controlled by the side dash switch, reverse the connections to that motor then be prepared for it to blow out years of junk that it has been inhaling.

[77newell]

Michael: thanks I will check that out. Having been into that metal box twice I can affirm that it is most unkind to the skin on my hands and arms. I think I checked for proper rotation but it is worth confirming.

I think there is another likely causation. It occurred to me during the night (never let a good sleep go to waste). The two dash blowers and the one for the arm rests are all situated in a single plenum above the air conditioning evaporator and the heater core. Air flows through a vent in the floor by the passenger seat, down a convoluted duct, makes a 180 degree turn up into the evaporator followed by the heater core, and then to the fan plenum. Given the resistance of that path, when the two dash fans are on they generate a slight vacuum trying to pull air through the convoluted path. That vacuum would pull air backwards down through the arm rest fan into the plenum, it's a path of little resistance. When that happens a bunch of air is bypassing the heater core and just going around in an unheated circle. I want to try measuring the temperature rise of the dash vents when the arm rest fan is on high. I suspect it will go up.If that is the case then whenever I want heat or cooling I will need to turn on the arm rest fan in order to get the best effect. I'll let you all know what I find.

[HoosierDaddy]

I am very interested in this as the dash heat is one thing that is on my to-do list!!!
Thank you Jon!!

[77newell]

Since my dash AC doesn't work and I'm not sure I want to try to ever make it work (they have a reputation for unreliability though it escapes me why that should be inherently true), it might make sense to remove the evaporator to reduce the air restriction it creates.

Another thing I noticed on this trip is that the vertical seal on the front sliding window leaks a bit and is pulling air out of the coach. I need to put more effort into making the coach more air tight since improving heater performance can be worthless if the heat doesn't stay where it belongs.

[77newell]

One more thing I learned on the trip home. When I turn the armrest fan on high the air from the other vents reduces. This suggests that air is struggling to get through the heater and a/c cores. I'll check that out soon.

The air leakage I thought I heard at the driver's side window seal was actually coming front the drains at the bottom of the window. Several of covers on the outside of these drain are missing. Anyone have a source for these?

[encantotom]

you should have penninsula motion windows. they will have the covers.

tom

[Richard]

Larry Brachfeld said to stuff some nylon ribbon in the hole to stop the whistling.

[77newell]

Thanks guys.

I took a look up through the outside vents in the bottom of the return air plenum. The bottom of the A/C core looks pristine, like new. So, I doubt it is plugged. Hmm, I guess more thinking to do, good thing I'm addicted to thinking.