Choctaw H140 - no ignition arc

[galaxie428]

I picked up a new to me Choctaw H140 duct heater earlier this week. I was excited to get it home and fire it up and see if it was going to work for what I was hoping to use it for. But, right now I just have an expensive duct fan. Vent mode is the only mode that works. I filled it up with off road diesel and it is switched to the internal tank side. I have fuel pressure in vent mode and I purge the fuel for 10+ seconds, then when I switch it over to cool down and look into the sight glass and I should see an ignition arc. I don't see anything. Unless I'm not looking in the right section, the TM just leads me to notify maintenance or something like that.

For those of you with these heaters, got any words of wisdom? What am I missing or what do I need to check on?

 

[155mm]

Look at atmosphere pressure switch

 

[155mm]

If you by accident bypass that switch, make darn sure the box is sealed up as much as possible other than minimal open doors for inspection

 

[galaxie428]

Thanks 155mm, I bypassed the switch and it worked. Now to find a replacement.

Does anyone know the part number for a compatible switch? I'm not finding anything online for the part number in the TM.

 

[155mm]

Clean it out, it get filled up with dust, then readjust, i think there is a procedure in the tm

 

[155mm]

If its bypassed, be overly overly cautious about keeping he box sealed up, if he box isnt sealed up, the heat exchanger can overheat and blow the end out, then you get flames and a big fan pushing the flames

I have one in Montana that has ran for 3 winters now bypassed, but the heater never runs with a door open

 

[galaxie428]

Is there a different TM other than TM 9-4520-271-14? That is the one I'm looking at and all I can find is "Repair is limited to replacement of defective parts". I may just leave it by passed if nothing else. I'll be the only one using it so I'll just make sure to keep the doors closed.

 

[155mm]

Yes, that is the only tm, did you attempt to clean and adjust? Adjustment is on page 0028 00-5

just dont forget its bypassed, if its only you operating it, i have no issues running it bypassed

 

[galaxie428]

I messed with it a little more today, pushed a little air through the tube with an air hose and blew something out of it. I felt it hit my hand but couldn't find what came out. I haven't done the tests yet, not enough hands and no clips on my tester. I'll have to mess with it more when it gets warmer. Too cold out to be without gloves very long. Thanks for your help though, it works with the switch bypassed for now.

 

[155mm]

If you are the only operator, run it forever bypassed. Heat is the important part

 

[galaxie428]

I bought some new flex duct to try out to see if it was going to do what I wanted it to. It worked pretty well but I only have vent mode again. I just used the heat on it a few months ago and everything was fine. I'm not getting the ignition arc again. I checked that the wires didn't come loose on the pressure switch and that looked fine. I added more diesel just in case that was the problem but it didn't help.

The one thing I noticed was that in vent mode, air was coming out of the stack and it smelled fumy. I don't recall that happening before but I could be wrong. I thought it only had exhaust in heat mode.

 

[155mm]

If I remember correctly, there is a burner chamber fan that forces air into the burner, remove top and inspect fan to burner duct

 

[Guyfang]

The fan is to completely empty the fuel system. What you should smell is fuel, if anything. Also a problem area was the flame senser. If its dirty, the thing will not light off. Can you heat the igniter popping off?

 

[galaxie428]

I removed the top and the duct from the fan to the burner duct looks good. Everything looks pretty clean in there.

I can hear the fan that goes to burner duct kick on or at least I think that is what it is but I don't hear an igniter clicking. With the top off, it that the metal box attached to the front of the burner duct with a capacitor on it?

I'd like to turn it on with the top off so I could see/hear what is going on but I assume I shouldn't do that?

 

[155mm]

You can turn it on with the top off, but no air will go around the heat exchanger if you try to start heater.