bus not heating

busshawg · November 17, 2008, 08:21:02 AM

Here I am again looking for some help. My 1984 MC9 is not heating in the passenger part of the bus. The coolant line in warm on one side of the valve (that is located in the front cargo compartment) and cooler on the other. The bus is producing nice hot air up in the drivers compartment which make me believe the lower valve isn't working properly. My question is has anyone ever replaced this electric valve with either a manual valve of maybe even just a rad hose? There is shut off vavles in the engine compartment which makes me wonder why I would install another vavle. I hope I have explained this so you guys know what I'm talking about. Thanks in advance.

Have fun

Jeremy · November 17, 2008, 09:59:12 AM

I cannot help directly with your question regarding the MC9 valve, but since you mention possibly replacing your electric valve with a manual one the following may be useful:

The equivalent valve in my bus is a manual valve operated by a cable from the dashboard. It is a variable valve rather than a simple on/off (ie. it alters the flow of hot water and thus heating to the rear of the bus). The cable was seized on mine, and I found spares available from www.thhs.co.uk. If it helps my value is Part No. CH9221 in the 'Heating Accessories' catalogue. I found that I recognised all sorts of bits and pieces from my bus in THHS' catalogues, so I'm sure it is a company I'll be using again.

Jeremy

Lin · November 17, 2008, 10:06:48 AM

I am not sure about the MC9 system, but my 5a has separate valves and piping for the driver and the bus system ( which I have removed). If that is the case with you, make sure that the heater and return valves at the engine are open. If the water is warm up to the valve, but cool beyond it, it would seem that the valve must be closed. You could experiment with trying to get it to open. Has the heat system worked before and just failed?

Tony LEE · November 17, 2008, 01:38:58 PM

That electric valve is normally open - open when there is no power to the coil.
Disconnect the coil and see if water flows. If it does, then the AC controller is holding the valve closed (as it does when in cooling mode until the set temperature is reached).
If no water flows then the valve may be stuck shut.

busshawg · November 17, 2008, 02:14:27 PM

Thanks guys, I have disconnected the wire and it doesn't seem to help.
I have removed most of my A/C components so maybe there is a wiring issue. I have also removed this valve and it seems somewhat restricted when I blow through it. Where would I find this A/C controller? Another fellow which has been a big help to me mentioned that there is a temp control thermostat in the duct work that might be shot.

The valve look almost new with new wire connections etc. This may idicate this has been a past problem. ( before I owned it) I have never tried the heat till now so I really don't know much about it other than the coolant is new last year when I replaced my rads and that the warm coolant is getting up to that point. Thanks

Have Fun!

Lin · November 17, 2008, 05:16:42 PM

If you have the valve off, it should be easy to test to see if it has continuity and opens/closes. What did you do to stop the coolant from draining when you removed that valve? Was there a manual shut off valve?

Tony LEE · November 17, 2008, 09:16:10 PM

"the warm coolant is getting up to that point"

There is probably some flow in that case. Have you checked that both isolating valves in the engine compartment are fully open - one up high above the gearbox and the other down near the starter motor.
Unless they fitted a normally closed valve, then if the water doesn't flow with the coil disconnected, it is a valve problem rather than a controller problem. If they completely removed the original AC system, they may have fitted a blanking plate in the circuit to stop uncontrolled heating while still allowing the demister to work.

Have you opened the hatch in the front wall of the front luggage bay to see if the radiator is even there.

busshawg · November 18, 2008, 10:55:07 AM

All I did was close the manual valves in the engine compartment , I only had a few gallons drain. I believe everything is working alright except the thermostat control valve. It's not allowing enough collant to pass through it to heat he core up. The core is there and if I leave the fan off the core will warm very slightly which tells me it has to be the thermostat control valve as it does get warm but is cool on the other side. I can't get power to it either on or off. I have the valve off so I will try to get it working on the bench then deal with my power issue I guess. Thanks for all your help.

Have fun