Hot Dawg HD45 Won't Ignite

[sixpackcuda]

My 4 year old Modine Hot Dawg (HD45) suddenly stopped igniting. Ran fine yesterday morning and now nothing.

It goes through the whole startup sequence, and a spark is visible, but it won't ignite. It makes the 5 attempts and goes into lockout.

Details:
Located in detached garage
Natural gas underground from house
Installed in 2019
Tried cleaning flame sensor and igniter with steel wool

I don't currently have a way to test gas pressure. I have a manometer coming in about a week. But over the last 4 years the gas supply hasn't been a problem. I have a multimeter, but would need someone to explain what to test and where.

Unfortunately this is where my knowledge and experience ends. I'm wondering if anyone can help?

 

[fitter30]

When spark starts gas valve gets powered. Check power at gas valve as soon as it starts to spark. If u have power on the gas valve remove the tubing for the vent it might be stopped up from a spider.

 

[PoorUB]

The Hotdawg get a call for heat from the thermostat, then the inducer starts, the inducer has to satisfy a pressure switch then the spark ignition starts and the gas valve opens. Once it fires it reads flame sense through the sensor. The sensor does nothing until the burner starts, no flame it times out and cycles again.

Are you certain it is sparking? If yes, check for 24 volt power at the gas valve. No power, maybe a broken wire, lose connection, bad circuit board. If there is power at the valve, then perhaps a bad valve, but make sure you have gas pressure before you condemn it. It might be the valve is stuck closed. I have gotten valves to open with a sharp rap from a wrench when they have power. About 50% of the time the continue to work. The rest of the time the valve gets replaced.

 

[sixpackcuda]

Thanks for the replies

I disconnected the two wires that connect to the gas valve and plugged in one probe from the multimeter to each wire. Called for heat and saw the voltage range between 26 and 28 before and during spark.

I tested the ohms on the gas valve and got a reading of about 1340

I tried giving it a few hard taps with a hammer, but nothing changed. However when I rest a hand on the valve, it does feel like there is movement inside.

I can definitely see the spark from the igniter

Verified that there are no obstructions in the venting

I also attached the probes to the pressure switch and the voltage went from 0 to 24 when applying very slight pressure to the tubing (i only thought to try this because i read about it in a different forum post)

Closed the shut-off valve and disconnected the inlet gas piping and there appears to be no obstructions there either. I can smell that there is gas, but can't verify pressure at the moment.

Testing with a multimeter is a little over my head, but hopefully I performed the tests correctly. Any other ideas?

 

[K13]

The boards go bad in them. Had the exact same problem replaced all the usual culprits didn't solve anything. Bought a new board problem solved.

 

[sixpackcuda]

I'd be inclined to agree with you K13 because I've had boards go bad in other appliances. I was just about to order one but thankfully that doesn't seem to be the issue.

I may have overlooked a basic step... But I believe I found the solution. I blew some compressed air around the burners and manifold. After that it fired up perfectly. Lesson learned I guess, would've been easier to try that first.

I'll report back if it has problems again, otherwise everything is running well

Thanks for everyone's input

 

[K13]

I would still be prepared to replace it. Mine would intermittently work until it didn't. It was the reason I replaced all the other small parts first. I would replace something per their recommendations and it would run fine for a week or two then quit. Replace something else and would run for awhile again then die again. It finally got to the point it would not restart at all.

 

[sixpackcuda]

Thanks, that's good to know. If it craps out on me again and a shot of air doesn't do the trick, I'll just bite the bullet and order a new board.

 

[larry4406]

@sixpackcuda

Let's see the 'Cuda!

 

[sixpackcuda]

Sorry to disappoint Larry.. wish I did, but I don't actually own one. As an admirer it's been my default handle for years. Maybe someday

 

[larry4406]

Sorry to disappoint Larry.. wish I did, but I don't actually own one. As an admirer it's been my default handle for years. Maybe someday

Me too! Hence the “4406” in my handle.

I’m part way there though. I have a stalled ‘71 barracuda vert project I’m cloning into a 440-6 ‘Cuda. Have most of the parts but not a lot of time. Other projects creep into the way.

Sorry for the thread derail. Grad you got the heater working.

 

[AC-WC]

Wonder if it was spider webs you blew out or maybe just dust?

 

[sixpackcuda]

Me too! Hence the “4406” in my handle.

I’m part way there though. I have a stalled ‘71 barracuda vert project I’m cloning into a 440-6 ‘Cuda. Have most of the parts but not a lot of time. Other projects creep into the way.

Sorry for the thread derail. Grad you got the heater working.

Wow, I'm jealous. I'd love to have a 'cuda project. Life gets busy, but hopefully you're able to finish it soon. Wish you the best!

Wonder if it was spider webs you blew out or maybe just dust?

Yeah it could have been either I suppose. There wasn't any visible spiderwebs and the dust was minimal, which is why I hadn't thought to blow it out initially. But obviously the air dislodged something. Unless it was a fluke and the board is actually going bad. If it ends up being the board or something else I'll try to remember to update this thread with any relevant information.

 

[sixpackcuda]

So it turns out that the compressed air solution was a fluke. The heater ran for another week and stopped igniting again.

I finally got my cheapo amazon manometer delivered, and determined there was zero pressure on the outlet side of the gas valve while the heater was attempting to ignite.

150 dollars later, I installed a new gas valve and it's been running perfect for two weeks so far. Hopefully this valve lasts longer...