1983 MC9 - Ex NJT - Coach heat MIA

plyonsMC9 · November 19, 2015, 03:45:31 PM

Good evening fellow bus-folk!

My coach bus heat is non-functional. Used to be that it worked so well that I had to make sure not to bake the passengers. Now, not so much. Just blows cold air.

What I've tried: both heater valves are 'open' in the engine compartment to allow the coolant to flow. Valve under driver seat on wall is also in the open position. Opened nut on the heater core by the driver seat - coolant immediately flows out. Put hands on hoses & pipe up front by outside panel - same location of the driver heater valve - the hoses & pipes are all cold to the touch even after running the bus for a period of time to where the temp gauges show the bus is warm.

Would greatly appreciate suggestions! Thanks all, Phil (Cold in the AZ mountains).

Iceni John · November 19, 2015, 04:14:06 PM

Has your coolant electric pump tripped its breaker or blown its fuse? if so, why? Does it share its circuit with something else - if it does, is that other thing also dead?

John

Debo · November 19, 2015, 11:36:17 PM

Good morning. I don't have my book in front of me, but I know there's also an electrically-operated valve located in the first bay on the curb side. Mine is located in the front of the bay up near the ceiling of the bay behind a little removable cover. At first glance it would appear to be part of the channel that runs the length of the bus, but it's a little hump with a removable cover. Hope this helps.

plyons · November 20, 2015, 02:44:37 AM

Hi all, on initial checkout yesterday we did not find any tripped breakers or blown fuses. However, will give that another shot. Did find about a foot long cover that we removed but didn't see a valve, so it must have been the wrong cover. It was adjacent to the channel that runs the length of the bus. Will get out to the bus a little later today.

Thank you very much for the responses!!

Kind Regards, Phil

bevans6 · November 20, 2015, 03:50:51 AM

There is going to be an electrical on/off valve somewhere that is controlled by the thermostat (temp sensor is usually in a passenger side return air floor duct) and the temp control dial up beside the driver. It simply causes the valve to be fully open or fully closed in response to the temp sensor and a comparator circuit that I never managed to figure out. My 1980 MC-5C has it located in the rear engine compartment (passenger side, low down, right beside the manual shut-off valve) in the main coolant return line from the heater coil in the middle of the bus. There is no electric coolant pump in this generation MCI. When the factory AC is on, the AC runs at max all the time and the temperature is controlled by the OTR heater adding heat to the cooled air.

plyonsMC9 · November 20, 2015, 10:16:46 AM

Ha! Who knew I had this- exactly as you all suspected - first bay, curb side. More testing to see if it's getting power. I see 24volts is listed.

Kind Regards, Phil

gumpy · November 20, 2015, 10:38:54 AM

If I'm not mistaken, that valve fails in the open position. That probably means that it's being held shut by the control circuit. Assuming you've played with the temp knob on the left, you may need
to check the relay circuit in the driver's side electrical panel. May be a relay in there, too. I can't recall right off.

Are you sure your gate valves are open and not broken. Does the center pipe heat up past the valve?

plyonsMC9 · November 20, 2015, 06:52:19 PM

Thanks Craig, it sounds like the idea is to run the bus 'till it heats up, then check the heat in the coolant pipes to/from the engine on both sides of the valve to determine whether the pipes are warm on both sides, or whether the temperature abruptly changes past the valves indicating they are closed?

Best Regards, Phil

TedCalvert · November 21, 2015, 02:16:54 AM

Good morning, and a frosty one it is here in SE Ohio.

Had a similar problem in my '86 Prevost. No heat in lines from engine room. One of the gate valves seemed like it took many turns and didn't really feel like it was opening. Drained, dismantled, could see no problem. Re-assembled.
At the same time, I took apart the solenoid valve up front and found the diaphragm rotted. When I rebuilt it found plunger stuck in the closed position within what Asco calls the "plug nut"; the core upon which the coil mounts. That held what was left of the diaphragm in the closed position. Got heat now!

BTW: I tried going directly to Asco for the valve, no kit available, nearly $300 with 3-4 week delivery. Kit was $150 or so from Prevost, 2 days.

Further BTW: This valve's components are rated for ethylene glycol service. If you're thinking of improvising some other valve, (I'm an improviser, sometimes) it may not last.

Now, how do I get rid of 20 gallons of used anti-freeze?

Oonrahnjay · November 21, 2015, 02:51:59 AM

Quote from: TedCalvert on November 21, 2015, 02:16:54 AM
Good morning, and a frosty one it is here in SE Ohio.

Had a similar problem in my '86 Prevost. No heat in lines from engine room. One of the gate valves seemed like it took many turns and didn't really feel like it was opening. Drained, dismantled, could see no problem. Re-assembled.
At the same time, I took apart the solenoid valve up front and found the diaphragm rotted. When I rebuilt it found plunger stuck in the closed position within what Asco calls the "plug nut"; the core upon which the coil mounts. That held what was left of the diaphragm in the closed position. Got heat now!

BTW: I tried going directly to Asco for the valve, no kit available, nearly $300 with 3-4 week delivery. Kit was $150 or so from Prevost, 2 days.

Further BTW: This valve's components are rated for ethylene glycol service. If you're thinking of improvising some other valve, (I'm an improviser, sometimes) it may not last.

Now, how do I get rid of 20 gallons of used anti-freeze?

Gary Throneberry ("Garhawk") had a similar problem with a solenoid-controlled valve in his coach in central Tennessee. I am pretty sure that we found that it was a wiring problem and not an internal failure, though. But it was same symptoms. On his coach, the valve that was giving problems is up in the very upper right rear corner -- the failure stopped warm water going to all the interior heat and defrost. It was a pretty frustrating problem but easy to trace down and fix. And, yeah, the fact that a hose that should have been warm was cold right after that valve was a big tip-off.

bigred · November 21, 2015, 11:09:27 AM

Ted :Our landfill's in N C accept used antifreeze.Might be a good place to start.

plyonsMC9 · November 21, 2015, 11:33:09 AM

Good afternoon bus folks,

I just ran the bus for a while. The attached picture shows the temp on the pipes to answer Craig's question.

For the wiring, to the valve in the front bay along the main chase, when I test, I'm looking for 24 volts, or?

Also attached a picture of the relay, but not sure what to do with that. Relay is labeled "Coach Heat Relay" on the diagram. This is in the front driver side panel, outside.

Thanks all very much!! Kind Regards, Phil

robertglines1 · November 21, 2015, 02:08:03 PM

Phil: I have one of those valves left over from my mci days. yours if you decide that is problem. Make sure it is getting power first. Mine was in same compartment the ac and Main heater core was in close to ceiling. bob

plyonsMC9 · November 21, 2015, 03:30:47 PM

Woo Hoo! OK. Thank you Bob. That's where ours is too. Will definitely let you know once investigations are completed.

TedCalvert · November 21, 2015, 04:15:11 PM

BigRed: Thanks for the suggestion; I'll look into that.

Pylons: My solenoid valve (Prevost) is normally-open, so if the controller is calling for heat, there should be no voltage on the solenoid valve's coil. Heat set point satisfied=voltage on coil=closed valve. Mine had a plug that I unplugged for testing. That's assuming it's a solenoid valve: either fully open or fully closed. I think my old 4104 had a variable valve originally, according to da book, IIRC. That would be a different animal. Also, if it's an ASCO valve, you can most likely pull the coil off to check the action of the valve. But a word of caution with that trick in other places: don't EVER pull an AC coil off of its core; it will draw lots of current and let the smoke out!

The relay might be to switch the larger current required by the pump motor. One really needs the diagrams, both electrical and cooling system, to figure out these problems.

HTH