OTR heater/blower

[Jim Eh.]

I have been having intermittent issue with my OTR heating. Last time I fired the bus up I had heat that would melt plastic but as I went for a short shakedown drive I had adjusted the temperature and cycled the fan off and on then noticed the heat was no longer working. I only had dash heat. I tried unplugging the water valve and used a laser thermometer but did not notice any change in the downstream temperature.
Can you disassemble the coil portion of the valve in place to manually cycle the water valve plunger? I really would rather not drain the coolant and have to work to get the system bleed if I can help it.
Also has anyone installed a rheostat on the fan to control the hurricane force wind coming out of the ducts? I would like to be able to keep the flow at 100% and control the blower.

[TomC]

I removed the OTR heat (no A/C since this was a Portland, Or bus). I mounted the heater element in the hallway under the refer and washer/dryer run with 2-14" 12v radiator fans-so no ducts. I took out the remote controlled valve, and installed a manual ball valve to cut off coolant in summer, but still have defroster work up front. I have a thermostat behind the driver's seat that only controls the fans. Once the fans do come on, you can count to 10 then feel the heat. Simple-works well. You could also change to this type-perhaps use only one blower if you can't slow down the speed. Good Luck, TomC

[Jim Eh.]

Good idea but I think I am past the stage to be able to re-arrange my heater system.
Also I plan on running my a/c system into the existing plenum so I don't want to take that system out. I was also thinking of just putting a simple ball valve in place of the air controlled water valve but still run the need for a fan controller of some type especially if I have no remote on the water valve. I had the notion of connecting a long manual cable for controlling the ball valve but now I am talking stepping back in technology and  convenience. Perhaps that is not a bad thing tho ....

[Jim Eh.]

As far as running additional/replacement heater cores I was thinking of running an additional rad at the front in the spare tire bay to aid in additional engine cooling. This would have to be on a thermostatically controlled water valve for sure though. I would connect this ahead of the heating system water valve to operate it independent of the heating system as I don't think I would be requiring both at the same time.

[richard5933]

If the air flow seems hurricane like, then maybe you don't have enough vents open to permit the proper flow.

Regarding the valve itself, I'm not sure if the one used in your bus is the same as in the GM. If it is, the GM manual does list a procedure for cleaning the shaft to help with problems like this. I was having some other work done which required draining the system though, so I opted to just replace the thing and be done with the problem. Once I got the new valve the temp would auto adjust according to the setting on the rheostat. However, it only does so within the limits set elsewhere in the system. I believe that there are only like 5 degrees of temp swing possible. For us, that means just below or just above 70F. In the winter I end up having to cycle the fan to regulate as it gets too warm otherwise on moderate days. The other thing of note is that the system takes a long time to actually make the adjustment, probably since ours is partially pneumatically controlled.

If you want a manual system, you can probably install a manual gate valve in your coolant lines that you can use to open/close the flow to the heater core. Depending on how your plumbing is routed it might even be possible to have the shaft of the manual valve stick out into the base of a cabinet somewhere.

[chessie4905]

Add a wall thermostat, and relay, if necessary to cycle the fan. I was going to do that on the 4104, but sold it before I got around to it.

[Jim Blackwood]

Jim, I'm guessing your MC12 is set up pretty much like my '96 DL3. If so, those valves can be had pretty reasonable if you make a thorough search. I swear I think I saw one for around $75, but twice that wouldn't be that bad.

I would imagine they are operated in an on-off fashion, and IIRC they need power and air to turn off. Can the valve stick in the off position? IDK, maybe. I guess you checked your airflow first though and if you have that and no heat then it must, and you unhooked it and didn't get heat you said. Sounds like a bad valve. I haven't been inside one but did you disconnect the air? If that didn't fix it, then it sounds like you may have to open things up.

As for the fan, depending on exactly what the motor is, (24vdc we know but brushless? Brushed? more info needed) it should be possible to run it using a solid state controller or servo amp that can be purchased off ebay at a reasonable cost, giving you infinitely controllable variable speed and reducing the energy requirements as well. I'll be looking into that as time goes on. Same for the condenser fans.

Jim

[buswarrior]

Best remember where that hot coolant comes from, and more importantly, where does it return to?

Failing to take enough heat out of the coolant as it passes through the heat exchanger...

And you get to overheat the engine via your self inflicted feedback loop.

As designed, there is always the specified air flow running through the heat exchanger, whenever the valve is popped open, heat or AC.

Don't mess with success?

Fix or replace the valve, manage the hurricane, enjoy?

Happy coaching!
Buswarrior

[Jim Eh.]

Thanks for the replies.
First there is at the present time only two openings for heated air release. These are the ones about 10' back of the drivers seat (both sides of the bus). I have removed the deflectors that were inside the kick enclosure at the base of the walls.
I only did a quick search on schmeebay and one valve was listed ... for 299.00 USD, about a bazillion CDN$ ( https://www.ebay.com/itm/MCI-16L-7-94-or-16L-7-97-HOT-WATER-VALVE/283233557702?hash=item41f2091cc6:g:snkAAOSwkHFcKYNO ) so I am looking at other solutions.
As far as the concern about creating an engine cooling issue. This one has me worried and puzzled. If the system WAS working properly, doesn't the valve shut off via the air controlled solenoid? If the fan is shut off then there is NO air flow through the heater core (exhanger).

[buswarrior]

The operating logic is for the valve to be closed while engine is on, unless the HVAC control commands it to open.

Without some sort of duct work, yes, there's going to be quite a breeze blowing out of those holes in the floor, and you will have a devil of a time getting any heat to go down the back.
The hurricane will head forward to the return air intake.

However, in proper winter conditions, even compromised, it still beats most of the popular options.

You are somewhat stuck from a design standpoint.

Stock heat needs to be regulated, and needs to be ducted to distribute the heat evenly.

Stock heat really works well in extreme conditions, when the other methods leave you cold.

Can you figure out a duct system of some sort?

After being absolutely sure the air signal to the valve is working as intended... by measuring it right at the valve... it would be really depressing to find the controlling solenoid the culprit and not the valve... after doing all that work...

Then I would re-build the valve. They are intended to be serviced. Call MCI to confirm parts availability, take yours apart, and order what is needed.

I would expect the "repair kit" listed in the manual will solve the common problems, otherwise it wouldn't be a kit?  Orifice seal, valve spring, stem guide and seal, and vessel seal.

Difficult decisions when so many aspects of "stock" are compromised.

Happy coaching!
Buswarrior

[richard5933]

Have you called Luke? Odds are, if a rebuild kit exists he has one. Or, he may have a used part from a parts coach that's still serviceable for repair parts.

Yes, that part from MCI is not cheap, but if you try to rig some alternative system in place I suspect you'll end up spending almost as much, just do it piecemeal, and then have a system that doesn't work as well as OEM.

A agree on the ducting. The HVAC fan in there is going to be huge for just the small opening you've got and will certainly end up with high air velocity. Shouldn't be too difficult to reopen some of the original ducting if it's still hiding behind cabinets, etc. Otherwise, perhaps you can run some new ducting. Wouldn't hurt to allow some of it to hit the wet bay area, and it would help keep your wet bay warm while traveling in winter conditions.

[Jim Blackwood]

Assuming you will be installing some sort of cabinetry, that makes the ducting a bit easier, at least on one side since you can just open it into the back side of the cabinets, which then lets you vent it out the toe kick, put a register on the end cabinet, cut a duct into the bath/bedroom, etc. Might take some creative genius but it can/has been done that way and you should even be able to work your way around the fridge. Slide-outs would be a challenge but even directing the air behind a couch will help disperse the airflow.

I agree with BW, make sure the electric/air part of the valve is responding to commands and then rebuild the air/fluid part of the valve. You will get wet, but it sounds like that's going to happen anyway. No other solution will get you as much heat as cheaply. That's about the going rate for those valves but if you don't have to have it "right now" you can find them for less. Get the part number and do a P/N search. That often helps.

Jim

[Jim Eh.]

Yes ducting is definitely in the plans. As suggested a small pair of ducts into the "wet" bay among others, are reasons I turfed the original duct work. I did save most of the SS covering but I think it will not be needed and gobbles up too much room anyway. I am not too concerned about keeping my side windows in the living room/kitchen clear while on the road so I will route the heat other places. Lots of room in the cabinet bases to run small ducts but without knowing too much about airflow calculations I am just going to "wing" it (pun intended).
I may try the old suction trick to take the valve out of the loop and slip in a straight filler while I check/rebuild the valve.

[richard5933]

Does the valve in your coolant line connect to hard tubing or to rubber hose? If rubber hose, is it possible to use a pair of hose-pinch clamps to shut off the flow while you pull the pump? That's what I did on my Webasto when I had to change a pump. A pair of gadgets that look like modified Vise-Grips held the hoses pinched shut while I took my time changing things out.

[buswarrior]

The rads are higher than the valve...

Close the supply and return valves back in the engine room, close the driver's heat valve, and prepare a big pan, you'll only have what's in the length of the highest pipe runs, from back there, up to up there.

When you are done, open valves and pour it all back into the usual rad filling place.

Defroster heater core will typically need air bled off.

On ducting... home brew ducting with high velocity air often makes unpleasant noises.

Buses all put the heat up the outside walls, because the cold REALLY comes thru the walls and windows... put the heat right where the cold is, and the interior stays pleasant. Cold drafts aren't fun.

A couple transit manufacturers thought they'd be smart, and just use the ceiling air circulators... radiant heat all around the perimeter now... and your shoulder still gets cold thru your coat sitting by the window...

Happy coaching!
Buswarrior