Tried turning on the furnace in our apartment unit but it does not turn on. When the thermostat is turned up, I can hear it click on by the furnace in the basement. The LED on the main board of the furnace blinks 3 times; according to error code listing, it is a vent problem. Auto pilot does not turn on and vent blower does not turn on. Any advice as to what I can do to fix this?

 

Welcome to the forums.

First off..... you said apartment. A furnace repair needs to be handled by the owner or an authorized company of his choosing.

Secondly.... a make and model of the furnace would be required.
You could have a defective draft inducer motor or the control board could be at fault.

 

Furnace is a Goodman model GMPN080-4 REV B with serial no. 9809627741.

 

FYI that furnace was built Nov 1998. is the inducer motor running?

 

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When the thermostat calls for heat, the circuit board should turn on the 120 VAC power to start the inducer motor, which circulates air to burn the gas.

That's probably the click you hear, but presumably the inducer motor isn;t starting and coming up to speed. I'd start by check to see if you have 120 VAC being supplied to the inducer motor when you turn up the thermostat and hear the click.

If the motor does have power to it but it's not starting, I'd pull the inducer motor assembly out and see what's happening. The motor might be seized up or have some other problem. If so, you probably need a new inducer motor assembly which provides a new motor, fan and other parts as a unit which can easily be bolted in place.

If you have no 120 VAC being turned on, you may have a bad circuit board that isn't switching on the power properly. Also check to be sure that the thermostat is actually sending 24 VAC to the W terminal.

 

Is there any type of overload protection on the inducer motor? Could a fuse be blown? Why would the LED light be on if there was no power to the unit?

 

Could it also be a bad relay switch? I can't imagine the motor being bad on a unit that was built in 1998. Aside from a light coating of rust on a few of the burner elements and some dust on the circuit board, the unit looks brand new.

 

If that is the original motor I wouldn't be surprised the motor is bad. Not likely a fuse problem. Do you have a volt meter?

 

The inducer motor is protected internally and there are no external fuses for it.
Could it be a bad relay.... yes very likely.... which means you may be changing the control board as the relay is on it and is not repairable.

 

No, I don't have one but I can get one. If I were to check it with a multimeter, what would I check for? I am assuming checking for voltage cross the pos and neg leads? Anything else to check for?

 

Checked power going to main board, I have 120 V going to it (door switch depressed). Red LED glows red when furnace thermostat turned down, but starts blinking 3 times when I turn up the thermostat. Anything else I need to check voltage on? What about blower motor?

 

This is the manual for your furnace. goodman - gmpn.pdf

In the diagram I highlighted where you need to check for 120vac when the furnace starts to call for heat. If there is no 120vac here it would mean a board/relay problem. If there is 120vac then the inducer motor is bad.

 

When I turn up the thermostat and depress the door switch, I get 120V across the hot and neutral terminals you have labeled in the schematic. I guess it's a bad inducer motor?

Bryan

 

The INDucer terminal should only have 120v on it during a call for heat. If that is the case then it would appear the inducer motor is defective.

 

Never tested the voltage across those terminals without the heat turned up. Probably should so a bad relay could be ruled out without a doubt?

 

Any idea how much a new inducer motor would cost and how easy it would be to replace myself? It appears that it is only held on by about three screws. The electrical connections are all spade connectors, so no soldering required.

 

Not too difficult to replace, but a few sites I checked want about $190.00 for the inducer.

 

If you replace it, but the inducer motor ASSEMBLY, which includes the motor, fan gasket(s) and the plastic or sheet metal parts that make it easy to bolt the new part in place, using the three bolts you've described.

 

Another question to ask: is there a chance the main blower in addition to the inducer is bad? Based on your guys experience, do you think this might be likely? if so, should I test the motor with my multimeter? How would I do this?

 

It's not likely that both blowers went bad at the same time. Does your thermostat have a FAN ON position ? Try that to test blower.

 

Nope, no fan on/off switch at the tstat.

 

Any other suggestions for testing the main blower? Can it be 'hotwired' on somehow? Or do you suggest just replacing the inducer motor and seeing what happens?

 

You obviously have an inducer issue so that should be addressed first.

In order to test the main blower motor.... tape or hold the blower door safety switch in.
Jumper from R to G where the thermostat wiring connects to the control board.
This should turn the blower on.

 

Tried to jumper between the R and G tstat connections on the control board with the door switch taped on. Main blower motor did not turn on. I tried I with the tstat turned up and down. Did I do something wrong? Any other ways to test the main blower motor?

 

Could the capacitor be the problem? If so, I guess I will have to find a multimeter with a capacitance test mode.

 

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If the capacitor were the problem, you would likely hear the motor trying to start.

More likely you have either a bad motor or a bad circuit board --- and a bad circuit board would be a lot more common reason for a fan motor to not turn on.

But you need to check to see if 120 VAC power is being switched on to the motor. If the voltage is being switched on and the motor isn't starting or trying to start, you probably have a bad motor, or perhaps a bad capacitor.

If no or little voltage is being switched on, you have a bad circuit board.

Instruments to measure capacitance aren't as readily available as those measured by a multimeter.

If you had a motor that had 1230 VAC to it and was trying to start, then I'd buy a new capacitor (which is usually pretty cheap) and see if that solved the problem.

 

I checked the capacitor on the motor using a method I found on a DIY HVAC website. I disconnected the leads to the capacitor, shorted the pos and neg connections on the cap, then measured the resistance of the cap using the highest setting on my multimeter as the one I have does not have a capacitance test mode. Since the resistance did not increase with time, this would tell me that I have a bad capacitor. I was getting 120V to the induced blower motor from the board, so I would assume that the board is fine. Did not test the relay to the main blower motor though. Will probably buy a new cap and test it out. What do you think of this?

 

Is there a multimeter you would recommend for troubleshooting this furnace? Make and model would be helpful as would the ability to purchase it from Lowe's or Home Depot or Ace Hardware. Doesn't have to be the best one out there, but have enough features and test modes to be able to thoroughly assess my furnace's condition (hopefully not FUBAR).