Motorhome Cab Heater Issue

Ken Freund Coach & Powertrain

by Ken Freund
February 19, 2015
Filed under Resources, RV Tech Q&A

 

I have a 2011 Damon Astoria 40KT. The issue is the dash heater; it seems insufficient to provide adequate comfort heating when traveling down the highway. When I first took possession of the coach, I noticed this and my local service technician said the baffles were not completely open, so he corrected it. But, it still does not seem to heat sufficiently. All this leads to my question: Can I safely run the motorhome furnace while traveling down the road for increased comfort?
W. Craig Adams | Fenton, Michigan

First, check the engine coolant temperature to make sure the thermostat is keeping the temperature up to specification. This should be around 190-195 degrees Fahrenheit. If that checks out OK, then yes, you can safely run the coach furnace. Obviously, you must remember to turn it off when refueling. Another option is an auxiliary cab heater. Just search “cab heater” on the Internet for a list of choices.

In really cold weather I have rigged up a clear plastic tarp that keeps heat in the cab area.

One Drip at a Time

Here is a perplexing problem. I have a GM 454 TBI engine installed in a 1994 Class A Winnebago 34-foot Vectra. It is an original installation with 27,300 miles on the clock. It runs like a fine watch, no malfunction indicator lights (MIL) or other known maladies. No overheating or abnormal temp or oil pressure; not even leaking exhaust headers.

Last spring, I found a small drip of antifreeze on the parking pad. Then I noticed that the drip seemed to occur every time the outside temperature fluctuated a few degrees. The reservoir level fluctuates normally between cold and hot levels.

The coach was parked for a week or two and I loosened the pressure cap. Having released all the pressure, and with the reservoir at the cold mark and the antifreeze at the throat of the radiator, I capped it again. It sat another week, again with fluctuating outside temperatures and outside barometric pressure changes, and a drip appeared. I got my camera and noted the only drip I could find was from the vent hole in the flex plate cover and, with the cover removed, between the oil pan and flywheel. There is no evidence of a leak from the intake or cylinder head gaskets from the top of the engine. The oil level is normal and there is no evidence of contamination.

Is there a frost plug or other exit point on the back of the engine above the pan and between the flex plate/transmission? Is it possible to have a cracked block without it having been frozen or overheated? Is there some way to fix whatever, wherever it is, without pulling the engine or transmission out?

Why is the cooling system under pressure after being relieved and not run again for an extended period? (I thought these engines were sealed at least from outside pressure changes.) Also, no additives or chemicals have been added to the antifreeze other than the 45 to 50 percent distilled water.
Doug Warnecke | Harwood, North Dakota

It is, indeed, unusual for the pressure to be maintained for such a long time. Typically, after the engine cools off, the pressure goes away. You might try a different pressure cap. Keeping pressure in the system will help the coolant find any tiny pinholes to leak through. It is unlikely, but possible, that the block has a tiny crack even if it wasn’t frozen. However, the more likely possibilities are that a core plug is rusting through or otherwise leaking.

With a 20-year-old engine I’d suspect rust, particularly based on the photo you sent showing so much rust in the area. There are several holes in the back of the block that have press-fit or threaded plugs. Often the press-fit plugs start to rust through. I’ve also seen blocks with porosity in the metal that results in a leak from a water passage. I had one of these and we drilled the block and welded it up. Screw-in or press-in plugs can be replaced fairly easily (once the transmission is removed). In any of these cases, the transmission has to come out to access the back of the block.

You could put a coolant pressure tester on it and subject the system to increased pressure to see if you can trigger a leak. Coolant dye and a black light can be used to help spot the source. Make certain it’s not running down from above.

I’m not a fan of stop-leak products, because they tend to clog heater cores and radiator tubes, etc. However, if you understand the risks, and are trying to postpone the need for a fairly expensive repair, you might try that first.

Auxiliary Cooling Fan

We have a 1991 Fleetwood Searcher 23-foot Class C on a Chevrolet G30 van chassis. There’s an electric cooling fan in front of the radiator that does not power up when the A/C is on. My regular repair technician used my factory GM electrical manual only to realize that it’s useless in regard to the fan. He applied power to it externally and the fan does work. It has a factory connector, but there’s no power going to the fan from anyplace he can find.

My question is, is it supposed to come on when the A/C is engaged, or does it only come on when the engine/coolant temperature goes way above normal, and where does it get power from? The dealer techs at GM are clueless. I took it to an auto electrical shop to no avail, and the Fleetwood techs weren’t helpful either. Any ideas?
Mike and Carol DeCastra | Homewood, Alabama

As I recall, the auxiliary fan on these models is controlled by a relay that is triggered by high coolant temperatures and/or when the air conditioning is on (this helps cool the condenser that is in front of the radiator, to help improve air-conditioning performance). If you can’t find a wiring diagram, follow the wiring back and try to find the relay and test it. Then test its inputs from the coolant sensor and A/C circuits. Alternatively, you could wire in your own continuous duty 30A relay to power the fan. The wire that powers the compressor clutch can be used to trigger the relay when the A/C is on. Power for the relay comes from the fuse box. You could also install a toggle switch under the dash and run wiring to operate the fan if the engine gets hot (the overheat circuit may still be working, but you don’t know). Put a diode in the wire so that power from the toggle switch doesn’t feed back and apply the compressor clutch.

Hard To Find 8.00 x 16.5 Tires

My 1989 Cobra Passport motorhome is 25 years old. It has a GMC chassis with a V-8 engine and is about 21 feet long. The tires are size 8.00 x 16.5 and are no longer available — unless I buy used tires. I already have used tires on my motorhome that I had installed about eight years ago, brand new. I called several local motorhome dealers in western New York state and nobody could help. 
I will need new wheels (rims) and new tires. Where do I find wheels (new or used)? I called a few auto wreckers/junk yards and they said they do not have any motorhome parts. Where can I get 16-inch inch wheels that will fit? 

David F. Quagliana | Williamsville, New York

You are right, they are getting hard to find, but not impossible. A quick search on eBay brought up several new 8.00 x 16.5 tires for less than $130 with shipping. You might also find some locally by calling around to tire dealers. You should be able to use 8.75 x 16.5 tires, which are more readily available, but you will have to change all tires at once. I found them online at www.thetirerack.com. If you decide to bite the bullet and change your wheels, 16 inchers should be easy to find in salvage yards. Instead of asking for motorhome wheels, look for wheels from a GM (Chevy) dually G30 or GMC G35 chassis.

Allison Angst

I have a 1997 Coachman Catalina with transmission problems. I just got the motorhome and I need advice on where to start. As I drove it home, I noticed that when the coach downshifted, the service light on the transmission gear selector came on. It also downshifted really hard going from fifth to fourth gear. I haven’t pulled the codes yet from the strip panel. It has an Allison 3060 transmission. I am going to service the motorhome, but want to know if there’s something else I need to keep an eye on. 


Brandon Robicheaux | Via email

Initially my response was to read the trouble codes to get an idea where to start. Soon, Robicheaux sent another email saying, “I think I have figured it out. The linkage on the injector pump for the tranny throttle position sensor (TPS) was worn out, so I built another bracket and installed it on the injector fuel linkage and reinstalled the TPS. I took a test drive and everything seems to be working fine now. No codes or hard downshifting.”

It is likely that other readers may encounter a similar problem, so I am passing along the solution, which may save a lot of time and money.

 


 

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