Inducer Fan Not Turning On

Deemar

Hi guys, thanks for helping me out, great forum! I have an issue with my furnace I'm really hoping you can help me out with. I have a Ultra V Tech 80 furnace and last week I turned it on for the first time since last winter, it blew hot air great. Some time over the following few days it got colder and I realized the furnace wasn't on anymore. I pulled off the front cover and it was blinking twice which corresponds to "Pressure switch stuck open, should be closed."

When I turn the furnace off and back on again, nothing happens. The inducer fan does not start, nothing turns on, nothing clicks, it only makes a constant low hum from somewhere inside. I took a look at the old Honeywell control board and there was brown charring around one of the parts so I just replaced it with the newer updated model, a ST9120U1011. I hooked it all up and still get the 2 blinks.

Here's what puzzles me, shortly after I turn the system back on, I can only assume it's trying to start the inducer motor to close the pressure switch and start the ignition sequence. However, if I pull the vacuum hose off the inducer and suck on it, I can easily get the pressure switch to close, and if I keep sucking, the inducer fan pops on and the furnace fires up perfectly. As soon as I stop sucking, the pressure switch opens and the heat stops. BUT, the inducer motors continues to run so if I put the vacuum hose back on the inducer motor, it'll continue the suction, close the pressure switch and the furnace works fine until it reaches temperature and shuts off again. Then once again it won't come back on because the pressure switch won't close.

So, what is my problem? Does the control board close the pressure switch causing the inducer fan to come on, or does the control board initialize the inducer fan which causes the pressure switch to close? If it's the former, I would assume my pressure switch is bad.

JJboy

disconnect the 2 wires connected on the pressure switch.....inducer motor should start working.....if work.....bad pressure switch

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.

Deemar

I just tried this. I unhooked the pressure switch, then turned the furnace on and nothing happened, the inducer did not start. I tried the trick with sucking on the hose and this time that didn't work neither. I couldn't get the inducer to come on at all.

JJboy

You have to measure the voltage on the inducer. If inducer is getting voltage using an ohmmeter check for resistance thought the inducer draft motor winding

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.

thestig3

Inducer motor energizes then closes pressure switch. Sounds like first board went bad cause high amp draw from inducer motor. With power off check to see how freely inducer motor spins, if any sort of resistance bearings would be bad, replace motor.

Deemar

Whoa, slow it down a little, getting a little beyond my knowledge. A week ago I didn't know how to open a furnace, I'm just learning as I go. I'm good with tools, I got a multimeter, what's a draft motor winding?

I tried this already as suggested from another forum I was reading, there's a grille over it but if I stick a screwdriver in there and flick the fan, it'll spin fine either way for a few seconds and come to a slow stop.

thestig3

Originally Posted by JJboy
You have to measure the voltage on the inducer. If inducer is getting voltage using an ohmmeter check for resistance thought the inducer draft motor winding
You can red motor winding resistance through the motor leads. If there is 0 ohms motor is bad.

biggles

tail wagging the dog.....again the pressure switch proofs out from the ID running thru the tube to give spak and main gas run...ring the motor winding meter jumps as if touching leads...then to the metal frame of the motor no reading as if your holding the leads in each hand if it rings true take an extension cord and slip the motor(no need to remove motor) leads into it if it runs the relay on the SS board is shot from amp draws over time...need to change the board

Deemar

Sorry I don't understand, where are the motor leads?

Sorry I can't understand this, what do you mean? What's spak?

I still don't understand, how do I ring a motor? I'm not familiar with any terminology.



You mean take the wires coming out of the motor and put them into the slots on the extension cord? You sure?

biggles

no problem you have an ohm meter so what where're looking for is when you touch the probes together and when there seperated....forget the actual resistance reading when you put them one on each motor lead.disconnect the motor wires where they connect onto the relay board..that point is where the board sends the 115V to run it on a heat call(first item to run when the stat calls....now take the leads and touch one to each wire going to that ID motor if the needle or led screen moves to from 1.0 to 000 or some valve just need to see continuity again as holding the probes together....OK no to check to see if their grounded same setting on meter one to one wire then other lead to motor frame the meter shouldn't move then do the other same any value show or goes directly to .000 the motor is grounded. if you have the readings i explained it might still not be the motor...take an extension cor and slid each motor lead into the cord the motor should run if its mnot mechanically fouled up......again this is all done with the motor inplace we are just working the wires....if the motor runs let it goe for 5 minutes then disconnect the cord grab the body of the motor see if its hot to touch or warm which is what we want...yes on warm the problem is the relay board.....sending 115Vs on a heat call.....get the info off the board tell you a soucre

Deemar

I can do this but maybe I don't have to, let me know if this means anything........when I suck on the vacuum tube to close the pressure switch, the inducer fan starts right up no problem. I left it running about 10 seconds and when I touched it, it was hot. Does that mean anything? Wouldn't it be normal for it to be hot where it's a motor and running so close to the flame? If that doesn't tell you anything then I'll try what you suggested.

Oh, also I replaced the control board yesterday with a brand new unit straight from a supplier. Model number in my first post.

JJboy

post some images, so we can show where are all parts

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.

Deemar

The old control board, does it look burnt on the left side? Is that bad?



The new control board hooked up.

thestig3

If your meter has the ability to check amperage then do a check. Clamp around 1 of the motor leads. If you have any amperage greater than listed on the motor then motor is bad. Oh yeah all this while equipment is running or attempting to anyway.

Deemar

Where's the motor lead? Where it connects to the board?