Blower Fan Won't Come On - DIY Chatroom

MichaelKB · 09-12-2009, 01:12 PM

Yesterday I noticed frost around my outside unit (split uint, furnace piece & blower upstairs). I thought maybe low freon, and read to turn the fan on alone to let it thaw in case the coil were frozen over. I let it do this for about 6 hours. (we left for awhile).

When we got back.. still no go. I noticed at this time no air was coming through the vents. I went upstairs and cracked open my unit, and there was NO ice on the coil left, BUT at this time I noticed the fan wasn't coming on at all.

I looked around on forums and read that you could test the thermostats by connecting the red to the green. Tried that, still no go, so I believe the thermostat is good. The breakers have all been set and reset. Last night while I was holding down the switch manually (wall switch that's closed when you take the side of the fan wall off, I suck at terminology), the unit kicked to life for about 5 seconds (until I let go of the switch to put the plate back on). It wouldn't fire back up again no matter what I did.

This morning I was reading and saw that the "block box with wires out both ends" was the relay and that maybe the issue. I'm not sure. I can hear the relay kick over, but nothing happens at that time. The little black box in mine is labeled transformer. Is that the relay? It gets very warm after the relay has clicked over.

Would it help if I posted a pic of the board? Or perhaps did some multimeter checks?

Thanks in advance!

yuri · 09-12-2009, 01:36 PM

Post a pic of the board and the complete make, model and serial # of the furnace.

MichaelKB · 09-12-2009, 08:40 PM

Some of the pics are kinda big, hopefully it's what's needed!

Make/Model Info:

Board:

Schematic:

The Transformer I was talking about that gets hot when it's on (but still not spinning the fan):

yuri · 09-13-2009, 12:08 AM

Check the pink 3 amp fuse on the board to see if it is blown. There is also a capacitor mounted on the fan housing for the motor and it may be faulty. You would need a capacitor tester to check it. Some multi meters can do that function. The relay is built inside the gray control board and the other item is your 24 volt transformer. Does the motor/fan spin easily by hand or is is stiff and seizing up?

MichaelKB · 09-13-2009, 08:03 PM

The motor turns very easily. And keeps on turning. It seems very well in shape. I took out the cap. and tried to measure with my multimeter, and couldn't get much a reading at all, so I'm thinking it's that. It's only $7 so I'm at least going to try and see if that does it. Thanks for the help!! I'll post my results (nobody is open today.. thank goodness it's cool and rainy out!)

Yoyizit · 09-13-2009, 09:18 PM

How hot does that 'former get?

no skin burn ever at 42°C(108°F)
burn in 30 sec at 54°C(129°F)
5 sec at 60°C(140°F)
1 sec at 71°C(160°F)

Keep the old cap; there's an easy way to check it with any voltmeter, a 9v battery and a Radio Shack 1 megohm resistor. Also, it wouldn't hurt to check the new one before you put it in.

kenmac · 09-13-2009, 11:00 PM

have you checked for power at the blower motor when it was time for it to come on ?? I would do this b-4 I started replacing parts.. Could be bad board

Flashheatingand · 09-13-2009, 11:52 PM

Look at the schematic: You see there are four tabs (heat, cool, spare1, and spare2). Remove one of the wires in the park position. Look at the schematic again, right below the hsir box, you will see two tabs (l1 and pr1) remove the wire in the pr1 tab. This will prevent the control board from energizing. Now plug one of the wires that was removed from the spare tab and insert it into the pr1 tab.
Push in the door switch. If the fan runs, you likely have a bad board. Now thats just internet advise. I am not there, and there is a possibility that something may be wrong with the transformer or something else that wasn't seen. But at this point you need to determine if the problem is within the load, or the control.

MichaelKB · 09-15-2009, 07:50 PM

Flashheatingand, I'll give that a shot. I bought a new capacitor to give it a shot and it was no go. I still here the relay click but nothing happens.

MichaelKB · 09-26-2009, 06:12 PM

Thanks for the tip! It's not the blower motor.. it's running right now wired like you suggested for testing. Now I guess I know it's the relay/board?

Quote:

Originally Posted by Flashheatingand

Look at the schematic: You see there are four tabs (heat, cool, spare1, and spare2). Remove one of the wires in the park position. Look at the schematic again, right below the hsir box, you will see two tabs (l1 and pr1) remove the wire in the pr1 tab. This will prevent the control board from energizing. Now plug one of the wires that was removed from the spare tab and insert it into the pr1 tab.
Push in the door switch. If the fan runs, you likely have a bad board. Now thats just internet advise. I am not there, and there is a possibility that something may be wrong with the transformer or something else that wasn't seen. But at this point you need to determine if the problem is within the load, or the control.

MichaelKB · 09-26-2009, 06:37 PM

I noticed this says direct replacement for a bunch of models, and I found my model number in there (58PAV090). Would this be the part I need to get up and running?
http://www.thecoolingstation.com/ind...roducts_id=117

Flashheatingand · 09-27-2009, 10:24 PM

Sorry Homey, your going to have to figure that one out on your own...

MichaelKB · 09-27-2009, 10:31 PM

lol.. man it's a hot night. I suppose running the spare to both the spot you told me (pr1) and the spot it was resting in would be a bad idea? I'm bout ready to rig it on for some sleep... lol

MichaelKB · 10-31-2009, 03:42 PM

I opened up my circuit board and took a look. Big black burn spot on my relay. If I can solder, and since it's only $1.30, is there any reason why I shouldn't fix it myself by soldering in the new part as opposed to buying the whole board for $195.00? The part is http://www.mouser.com/ProductDetail/...qY6CWmcjPlU%3D

Yoyizit · 10-31-2009, 04:06 PM

Quote:

Originally Posted by MichaelKB

is there any reason why I shouldn't fix it myself by soldering in the new part as opposed to buying the whole board for $195.00? The part is http://www.mouser.com/ProductDetail/...qY6CWmcjPlU%3D

If your furnace relay really does run on DC you might need a coil transient suppression diode unless it is already in this Mouser relay.