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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8517
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Goodman furnace model GMT 045-3 The aux fan starts...the

Customer Question

I have a Goodman furnace model GMT 045-3 The aux fan starts...the indicater light comes on...I hear a click but the ignightor doesn't glow...I looked at it ...there are no signs of cracks ....the indicater light doesn'tblink it just goes off with the aux fan motor
Submitted: 4 years ago.
Category: HVAC
Expert:  Phil replied 4 years ago.
All work to be done by licensed professional. WE KEEP GOING UNTIL YOU HAVE THE INFORMATION YOU NEED, I come and go. This is step ONE.

Hello, welcome to Just Answer!

There should be 2 clicks after the exhaust fan/ inducer fan comes on... the first click would be the pressure switch closing.. that happens within one or two seconds... the second click happens after 15 to 30 seconds (after the fan purges the fire box) ..then.. the ignitor relay clicks, and the ignitor should heat up.

It is when you hear the clicks that will point us to the cause.

Let me know about that. we can go from there.
Customer: replied 4 years ago.

I just hear the one click immediately

Expert:  Phil replied 4 years ago.
Hello again, thats the pressure switch contacts closing... they may be defective and not making good contact... unless they make good contact the ignition sequence stops right there, and the ignition relay will not close.

The test is easy, but precise.

Locate the pressure switch, it has one or two rubber tubes attached to, 1/4 inch in diameter... there should be 2 or 3 wire terminals on it.... if its only two terminals make a U shaped jumper wire, a paper clip will work... its only 24 volts...

and as soon as the fan starts hold the paper ciip jumper across the two terminals... if the unit fires after 15 or 30 seconds replace the pressure switch.

Tell me what you find and if you do the test tell me how it goes, we can proceed from there.

Next test would be to unplug the igniter module and check for 110 volts across the two female sockets on the ignitor plug after the pressure switch contacts close or are jumpered out.

(jumpering the pressure switch *before the fan starts will not work, you have to wait until the exhaust fan starts.)

We can go from there.
Customer: replied 4 years ago.

Thank you I'll test it now.

Expert:  Phil replied 4 years ago.

Customer: replied 4 years ago.

I replaced the pressure switch with a new one. and tested the ignitor plug there is no voltage to ignitor plug

Expert:  Phil replied 4 years ago.
Hello again, the term 'good' gets us in trouble... I need the details of the test so I know exactly what you did and what the results were.

Did you hear the ignitor relay click? If not, then it is most likely a bad control card.

Here is the manual on that unit. Look that over please tell me if thats what you have or not.

See wiring diagram on page 58, the ladder logic on top and the wiring diagram on the bottom, pay attention to the HSI and HSIR (two, contacts one circuit and coil on another).

The relay is built into the control card. its not closing due to a defect in the control card or one of the safety devices shown in the gas valve circuit open.... such as one of the ROS (flame roll out switches or pressure switches) you can jumper each of those one at a time as a test.

find the gas valve on the diagram then notice that one side is wired directly to the grounded side of the 24v transformer.. and the other side runs through the various safety switches.

Let me know what you discover.
Customer: replied 4 years ago.

Ok thanks after jumping the pressure switch again I get 3 red flashes pause 3 flashes

Expert:  Phil replied 4 years ago.
Hello again, see page 55 3 blinks. Notice the check out procedure on that line.... you can also jumper the pressure switch as a **brief test only***

Let me know how that goes.


Customer: replied 4 years ago.

Thank you Sir

Expert:  Phil replied 4 years ago.
Hello again, if you would like to rate my service so far i would appreciate it, its how the company pays me from the deposit pool. That will also allow you to continue on the same dime as necessary if you need to later.