Geoff Weeks

Found an online Red Dot catalog and punched in the number for the controller and they don't even list it in the parts section so suspect it is NLA from Red Dot and not likely from other sources. Bummer.

I did some digging in an older MEI Airsource catalog and came up with some stuff! Never noticed it before. There are two CTC resistors One looks like just the replacement (#1180) and the other is a "kit" with some mounting brackets (#1181) They also list a CTC control module (#1184) However, a word of caution. There is the CTC and CTC II system according to the Red Dot manual and I am not sure which these are for, or if they are still available. I get zero hits on a web search. That is about as far as I can get.

I took a screen shot of what the Red Dot manual has to say about diagnosing the CTC system. I also attached the manual. Neither are of much help the CTC is on page 131 Red Dot Manual

With out that air controlled coolant valve connected, (in the open/no air position) from what I can follow on the diagram, you should always have full heat. If you are not, I suspect someone installed another valve that is off, it may be the valves on the engine block, or it may be something they installed to control heat themselves and will not be on the drawing.

wow, completely different then what I was expecting and very different from the Red Dot systems I am used to on other trucks. You can forget most of what I wrote! Sorry if I led you a stray. Without those diagrams you'd be really up a creek! It looks like an early attempt to make an "electronically controlled " temperature system where you set it where you want it it controls heat and AC. I have never seen one like that, and there are many things that could be wrong. Worse, I have never seen PARTS for a system like that, esp the CTC board and such. May be someone else here has more experience with that system, I have never come across it. I believe CTC is an acronym for constant temp control. It looks like it uses a thermostat, resistor and board a long with air pistons and that air valve to control the heat and A/C. I think if worse comes to worse, find a way to bypass most of it so you have heat, and install and air switch to the air coolant valve so you can turn the heat off. They may use the CTC system to control frost on the AC evaporator, so to make the A/C system work (without the present system) you may have to install a frost switch. If no one here can help, I'd write Red Dot and see if they can be of any help.

My guess is there is another valve (likely on the block) or a valve controlled by a control cable that is not opening. I could be wrong, but if bypassing that valve doesn't work, follow the control cable to the valve that regulates the heat. make sure it is moving. Then check the valves on the block and make sure they are in the open position.

I bought mine from Manders Diesel for $250 per "kit". The kit was the motor, tank, tank mounts and controls (start button and relay valve). I bought two "kits" and they came with the voltmeter and low pressure light/buzzer from the 1st generation of Volvo's Roadway had. All I had to add was the -20 air line and the -6 control lines. I bought 2 because I wanted spare part in case I had a problem, I found them so reliable, that I converted my other truck to air start. The one that was too short to add an air tank on the frame, got the Maxwell ESM for electric cranking.

Getting back to the coolant valve. Could you post a picture of the heater/AC controls? If it is the Red Dot control I am thinking of, the air would come from it, when in Max A/C. Red Dot made lots of the heaters for trucks and would stencil the truck makers name on the controls. The one in my Marmon IIRC has one port that has air in the A/C position. Some one might have disconnected and plugged it at the control.

The solenoid is likely a continuous duty solenoid to switch power on with the key switch without all that power having to pass though the key switch.

No air = valve open, air to the valve = valve closed. They can stick, and leak as can any valve. I used them for heater and fuel heat control. They make air switches that look a lot like electrical switches from the front end, to control them manually those valves are "directional" in that they are only supposed to be used with the flow in one direction which is marked on the side of the valve with an arrow. While they can fail, I wouldn't say it is a common problem. I've used them for decades and not had a failure. I've had cable operated valves fail also. Note: those are either open or closed, there is no part way or throttling to adjust heat. Some A/C controls will supply air to the valve when in "max A/C" to stop all coolant flow in the heater core for better cooling. If you want, you can bypass it and see if you get heat, just put a straight tube between the hoses. I often see them in bunk heater -A/C units to turn off the coolant to the heater core when not in use.

I believe you are correct.

Larry, you likely have the 150BMP series I linked the draw above. That is what I have also, very robust. I-R still lists them in their catalog, but everything is going turbine now. Motor segments are aluminum, drive nose is iron. rear housing/cover looks slightly different then the more modern ones, but that is it. May be they updated the rear housing. Other than that it looks like a 150 of today.

Yeah, that is an obsolete model. You will not find "kits" for it but you may find vanes that are the same that could be used. As others have said, be careful when dis assembling to mark orientation of the segments as you disassemble. Gaskets can be made and they don't have to be 100% air tight. It only sees air when starting and a minor leak isn't going to be missed with the volume of air that thing uses. Try and get the gasket thickness the same as what you remove. If you look at the drawing I linked the vanes are listed as 10BM-42 which may mean they are a hold-over from the old BM series, you'd have to take a gamble and check. Other parts in the drawing start with 150BMP-xxx and are likely 150 parts only. I believe that model uses an "inertia engaged" type starter drive, so clean the drive end of all the muck so the drive will slide out easily. Good luck. I think it will "live again".

It might have been on JOT or even ATHS.

didn't Larry @Freightrain have BM series? I don't know if he found parts for it or replaced it or just got it working. I remember (may be falsely) that it what he had. It pre-dates the BMP 150 series, and was replaced by it.