About to attempt to fix my House Heater - no heat

[movingzachb]

I have just signed up for this forum - and no i have not done a search but I will. I just want to post while things are fresh in my mind.

I have been doing some research to find out what is going on with my heater. I am looking for some free online help - as it is the time when I NEED heat now and cash flow is simply not available to pay for a service to come out and fiddle with it.

I have a Robert Shaw 9600 Thermostat - everything seems to work but there is no heat blowing. I can turn it on and hear it buzzing on the roof (opening the unit I can see its the fan engine spinning).

What I have done is:

- The 9600 Has a (in order) Red, White, Yellow and Green wire. Between the Common and the yellow or green wire I get 28 on the Voltage meter. White and Common I get .14. All other functions of the Robert Shaw 9600 Thermostat appear to be working.

- Got up on the roof and checked the units fuses - look fine.

- When it is powered on the fan motor starts and then you hear a minor click where it is attempting to ignite gas but nothing is happening.

- The solenoids don't appear to be getting power to ignite it, I verified this by checking the voltage coming from the Johnson Controls MG770 NGC-7 (this is an older unit there replacement is the Johnson Controls G770NHC-1C).

http://www.allthermalcontrols.com/product501.html

This unit is screwed in and looks very simple to replace as long as I put everything back in the right order with the new unit.

What I am concerned about is that I did read something about a exhaust fan being plugged or something like that. Where could make and adjustment to allow air to blow and ignite the gass (and this could be the issue) - however after checking voltage on the Johnson Conrtrols unit - this tells me the unit has failed I also wonder then how the fan is getting its power (maybe its routed differently and my heater is just locked out).

Here is where I posted my question still yet to be answered on the fixya site.

http://www.fixya.com/support/t1213722-thermostat_wont_turn_heater_robert_shaw

Any help or assistance with how to go about this is much appreciated.

 

[skippy]

I read your post several times,sounds like the johnson ignition module or the gas valve.Hard to say without looking and troubleshooting myself.

The price for the replacement module seems twice as high as I would expect to pay.Do you have a grainger store nearby where you could compare prices,you could also probably cross the module over to a honeywell version.

From what I read,the normal heat sequence is running until lockout due to misfire.I suspect the ignition module,reset the unit by turning off power and then check for 24 volts from mv on the module,if durring the trial for ignition 24 volts fails to show up and unit locks out,change that module.

 

[skippy]

I read your post several times,sounds like the johnson ignition module or the gas valve.Hard to say without looking and troubleshooting myself.

The price for the replacement module seems twice as high as I would expect to pay.Do you have a grainger store nearby where you could compare prices,you could also probably cross the module over to a honeywell version.

From what I read,the normal heat sequence is running until lockout due to misfire.I suspect the ignition module,reset the unit by turning off power and then check for 24 volts from mv on the module,if durring the trial for ignition 24 volts fails to show up and unit locks out,change that module.

Also check the airflow switch with the air tube going to it.Just take the wires off and check for continuity through the switch with purge fan running.If no continuity and tube is intact that coud be the problem as well.