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Rick Mather
Rick Mather, HVAC Technician
Category: HVAC
Satisfied Customers: 3634
Experience:  35 years experience, HVAC
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I have a Dynavent heater that will not ignite. Blower runs,

Customer Question

I have a Dynavent heater that will not ignite. Blower runs, and I can hear the microswitch click. Glo-bar does not glow, and I detect no voltage in the leads to the glo-bar. Glo-bar tests at 1.5K ohms. I hear no click of the solenoid valve. With the thermostat turned off, the time-delay shutdown works.
The unit is installed in a difficult overhead location, so I was hoping to find the problem without removing the core, but I suspect this will be necessary.
Submitted: 7 years ago.
Category: HVAC
Expert:  Rick Mather replied 7 years ago.

If your induced draft fan is starting but maybe the pressure switch is not making clean the hoses and ports they attcach too see link for what they look like

Customer: replied 7 years ago.

I don't understand your answer. Are you saying that I should remove and check the sail microswitch? What hoses and ports are you refering to?

I do not see the link you mention.

Customer: replied 7 years ago.
The Dynavent heater does not have a pressure switch with ports as you suggest. It has a microswitch with a sail that activates the ignition circuit once the blower runs. I can move the switch and I hear it click, and the blower seems to be working at the poper speed. Do you mean I should remove and test the microswitch? If the microswitch works properly, would it most likely be the ignition circuit board?
Expert:  Rick Mather replied 7 years ago.
Maybe it does not work when flow is against it
Customer: replied 7 years ago.

It seems I will have to pull out the heater core to get at the microswitch, and test it under blower operation. If it does not close, or if it does but the circuit remains open, it seems that I should change the microswitch. I may try that in a couple of days.

If the microswitch tests out ok, then what?

Expert:  Rick Mather replied 7 years ago.
Well then we keep looking
Customer: replied 7 years ago.

OK, I have the core out.

Micro switch with sail works.

No 24v at yellow and green wires.

110v present at white and blue wires.

No voltage to glow-bar.

Blower comes on with time delay, shuts down with delay.

I reconnected the ignition board, and NOW, after about 90 seconds, the glowbar lights and the burner ignites.

I reinstalled and reconnected the gas, tried it again, but it wouldn't ignite until I tapped on the circuit board. If this happens again, replace the board, right? Sounds like a bad relay on the board. It's a $200 part, so I would like to get it right.

Expert:  Rick Mather replied 7 years ago.
Well at least you found something!
Rick Mather and other HVAC Specialists are ready to help you
Customer: replied 7 years ago.

Your answers provided me with little aid in finding my problem. It appears I have a bad connection somewhere, as removing and replacing the core, together with testing the connections, seems to have restored normal operation without actually replacing anything. Ironically, this is something I probably would not have done without you responses being so vague.

I downloaded and reviewed the owners manual and troubleshooting guide, and followed their flowchart. Although I did not pinpoint the exact problem, it gave me actual directions. To the extent that your answers compelled me to do this, they were some help.

Expert:  Rick Mather replied 7 years ago.
Well you did not have to accept but I thank you