Thermostats

[buswarrior]

What is controlling the coach interior temperature?

The D model did not have electronic controls for the dashboard/defroster/driver, just the cable to coolant valve, and the defroster fan switch.
Retrofitting one would be obscene, even for a public utility...

What is mounted in the forward face of the driver's modesty panel? The panel between the stairs and the driver's seat. Should be a square push in, pop out, switch mounted there, facing forward. Electro-pneumatic fresh air control.

Is the green light for a "heater" or for "heat"? An indicator light that the coolant valve is open and feeding the heat exchanger is different from an indicator that the coolant boiler is burning.

You have to nail down existing, working or not, otherwise the journey gets rougher, not smoother.

Happy coaching!
Buswarrior

[Jim Blackwood]

Yep. Guess I wasn't clear but the main midships unit has a electro-pneumatic water valve to control main coach heat, which is operated by a thermostatic controller in the mid-right hand side of the dash. Looks like that probably works as intended, it has a visible digital set point and an indicator light. I've run it through one or two operating cycles and believe it does work. Other than the coolant it is totally independent of the dash heat.

It's the dash heat we've been talking about. I have the covers off and the spare tire pulled and have access to all areas. The coolant has a T-handle cable operated ball valve. The fresh air damper has a cable which is damaged and has had the sheath and cable cut in the tire well and zip tied out of the way. No indication of where it went or what it hooked to but there are no holes by the water control cable for it to go through the floor.

Yes, you are right about the square button, (on the front of the shifter console) I had forgotten about that. So there should be a solenoid of some type on the cable but there is not. The easy fix, if I can get a suitable cable is to put another T-handle by the existing one, like the earlier coaches used. This would give better control of the damper as well and I'm inclined to go that route. It would make relocating the shifter console easier as well, if I decided to do that later on.

The green light indicates that the burner is on, so that's good. I think the small red LED on the main digital controller tells when the main valve is open. I don't know of anything showing when the water pump is running.

That leaves the timer which is straightforward enough at this point, and the square controller which is mounted in the same pod.

I don't know what that square controller does. Aside from the water pump (which I think is controlled from the boiler) I have run out of things for it to do. It has 4 or 5 wires connected to it and I saw no obvious interconnect to the timer. So that's the big mystery, I think everything else is accounted for.

Jim

[buswarrior]

Follow the wires from that square controller and see what they connect to.

The schematic in the book will tell you the terminal usage, if they head for the big terminal board.

It would not surprise me that previous owner chopped the fresh air controlling machine out of a coach they were selling.

That is the fresh air intake for the whole coach, follow the duct to where it feeds into the HVAC compartment/coach interior air intake.

The "for sale" coaches are often/always picked over for spares before they leave...

Manually controlling the ball valve for dash heat is the best system for the dash heat, MCI or Prevost. All the newer electronic temperature displaying or twist knob things all have hair triggers, too hot, too cool... and the displayed temps are meaningless, when you are trying to stay warm with that giant cold wall of giant windshield sucking the heat out of the space at the front.

Happy coaching!
Buswarrior

[Jim Blackwood]

The hatchet job wasn't recent, the cut end of the cable is rusted. The 2mm wire on the damper door was all bent up and disconnected. Guess that solenoid just got a little too energetic pushing the door open. It could have been cannibalized, after all they did steal the back bumper. Haven't seen anything else though.

That square controller is an MCI part. Has their name on the front of it. In the Operator's manual they show it in a drawing of the pod with a newer model Espar timer next to it instead of the 99 hour timer that I have. It has a knob and a red led light that comes on when main power is switched on.

BTW the DL's have two fresh air intakes. The left one goes to the main system (RIGHT! That is the one controlled by the square button and the big butterfly valve! That's why I didn't remember it, there's nothing to do with the dash air.) and the right one goes to the damper flap up under the heater-AC matrix in the dash. So maybe that controller does run the whatever sort of device they used to run that cable to the damper door in and out. That does sort of make sense, a proportional control would let you dial in how much you wanted the door open by using the knob. The wires are going to be quite difficult to trace as they disappear behind a cover in a big bundle of similar wires then reappear coming into the junction box from a different direction. That's a job for nice weather, that is.

Jim

[luvrbus]

The D's have a aquastat some place to control the boiler when the Tstat calls for heat mine does

[Jim Blackwood]

Is that separate from the boiler itself?

Jim

[Jim Blackwood]

Here is the controller that I'm having trouble identifying its function. Model # 7L-8-1257, S/N: K0508AT-002. Superseded by a unit which has a digital display and push buttons for setting, it is apparently a temperature controller with an internal relay. But controller of what? In the 3rd photo you can clearly see the controller that handles cabin heat via the solenoid control valve above the main heater matrix. Dash air is via manual cable valve, overhead heat maybe? They each have an independent thermostat built in but maybe that is for the A/C and doesn't handle the heat? I think it would have to be that or the damper control.

Jim

[buswarrior]

You have an illegitimate bastard on your hands.

If it isn't in the book, you have no easy way out, you need to trace the wires and see what it is connected to.

The part is one of the variants for plugging into the dash to control coach interior heat. Notice the similar style to the other one.

It could just as readily be a broken one, that someone thought looked better in the old Webasto hole, than leaving it garishly empty... if we can imagine it, you can be sure someone working on a bus has done it, and more...

These coaches have no need for fancy fresh air intake control. Basically, in a functioning coach, it is left open. Windows fog up and ice up in winter with a load of people onboard with it closed... and the coach quickly starts to stink inside in summer, if fresh air is cut off in some wasted effort to make a half broken AC work better.

As you found, the control has been ripped out for awhile, with no ill effects.

The dashboard fresh air inlet is the only one that you routinely close for summertime AC use, as it is proportionally bigger and can overwhelm the dash evaporator.

So... start tracing wires and see what it is connected to...

Happy coaching!
Buswarrior

[Jim Blackwood]

OK I found it. It's called an (Optional) "Driver's Temperature Control" (DTC). It controls the (Optional) Driver's hot water Solenoid Valve. So there we have it, straight from the Operator's manual.

Today I had the interior of the bus up to 85° on the main heater control (which works correctly btw) and at that point the DTC was shutting off the red indicator light near full scale on the adjuster knob which was similar to what the main controller was doing. (Can't say it wasn't working at lower temps, I discovered it has a delay which I wasn't waiting for so it probably does.) So internally it seems to be working right. Didn't affect my readings on the in-dash heater matrix though. It got up to about 155-160° and stayed there. And here's the puzzle.

I have a ball valve with a manual control for the driver's heat. The maintenance manual shows a standard cable operated ball valve and an optional electric solenoid valve. I suppose it's possible some yahoo cut off the damper cable (since it's always open anyway or because it didn't work anyway), yanked out the solenoid valve, put in a ball valve, hooked the end of the damper cable to it and called it good? I could see that happening maybe. Then got into the damper and disconnected the end of the wire from the flapper and just positioned it where they wanted it.

Which makes the DTC redundant and leaves the damper literally flapping in the wind. I think I need to revert to original, which means I need a new electric solenoid valve, a new air damper cable, and to find the wires that hook to the solenoid valve.

Jim

--- I think ultimately I will put the controller in the square hole in the dash instead of back in the pod. In fact I think I'll just get rid of the pod since the thermostat I ordered for the boiler is smaller and a different shape. I'll find some other place for that to go.

[buswarrior]

Don't assume anything...

Coach could have been in a horrific accident, and whole dashboard from another donor coach installed.

Which came first, the chicken or the egg?

What actually was stock, remains to be seen.

You won't be happy with electronic controlled dash heat...

Happy coaching!
Buswarrior

[Jim Blackwood]

Clearly I should take your advice on that.
Plus it should be cheaper anyway to just install a new damper cable. Only have to drill a couple holes. Maybe the new thermostat for the boiler can go in that blank hole on the dash. (may not be the best place for it though) Of course, replacing the cable connection at the damper end is going to be a real challenge. But it has to be done in any case.

Just guessing here, with the electronic controls it gets hot, then cold, then hot, then cold and never settles down to the right temp? That'd make sense given the hardware. I bet the controller out of say a Lincoln would work lots better but then that'd be 12v. Essentially it looks just like a standard industrial PID controller (I may even have one kicking around somewhere) so probably it just isn't calibrated right. (But how the heck would you recalibrate it? Serial connection maybe? Who knows. Too much other stuff to do, it can always come later, maybe never.)

I know I shouldn't assume anything, I've seen the work of lots of DPO's before. But this is the first scenario where everything matches up between the bus, the manuals, and the serial numbers and it also makes sense. So I think it's safe to go with it. Having done that, I think you are exactly right and a retrofit to an earlier VIN with the cable control is the best answer. Or the same VIN with the standard controls really.

So... any suggestions as to where I might get the correct control cable for the dashboard fresh air damper without breaking the bank? MCI? Luke? Someone else?

Jim

[buswarrior]

Any old cable and sleeve from a local supplier. Measure for what you need.

Used to be a generic "choke cable" in the auto parts "universal parts" section that might fit the bill for a couple dollars. T handle and all.

My guess is MCI will be very proud of those, but try 'em, sometimes we get a pleasant surprise.

Whatever you use, lube it up well before install, put it on your preventive maintenance list, and protect the business end from splash. Yes, water gets in there, that's why the stock ones seize.

Happy coaching!
Buswarrior

[Jim Blackwood]

You know, I haven't been able to find anything near that robust so far. It has a 2mm (.080") control wire and a very hefty handle. Nothing NAPA carries even comes close.

Jim

[richard5933]

Have you tried Mill Supply? I did a quick search and found this: https://www.millsupply.com/cable-54062.php?p=97809

I'm sure that they have others if this isn't going to work.

[Jim Blackwood]

Guys, do you have any idea just how huge a 2mm control wire is? Even the fattest ones you can find at the box store usually aren't over 1mm and never are larger than 1/16" (about 1-1/2mm). A 2mm wire has 4 times the mass of a 1mm wire. It's a whole different animal.

Jim