Hi,

The blower motor in the indoor unit of my heat pump stopped working a few days ago. Outside unit comes on, outdoor fan comes on, pipe heats up going into air handler.

The squirrel cage fan in the air handler spins easily by hand, and keeps spinning for about 60 seconds, nice and quiet and smooth.

Hoping it is just the capacitor. The capacitor looks great, though, nice and clean, no bulges. But it is kind of old though, has 36 years on it. Blower motor also is 36 years old.

I want to take the capacitor out and take it to some hvac place and see if they will be nice enough to test it for me.

Before this happened, everything was fine. Getting good heat, no aux needed.

Would anything in the outside unit cause the inside blower motor to not come on?

It is a Trane XE1000. I have been taking good care of it, inside and out, cleaning fins on the inside and outside, keeping snow off of it, etc, and not using it much, really, keep it cold in winter and warm in summer.

Attaching some pics of the air handler insides. I think the rectangular silver part attached to the fan housing must be the capacitor.

Thanks for any help !


Trane XE1000 air handler

 

Yes... the red arrow is pointing to the capacitor.
You would need to remove it to get the specs off of it.
Will be something like 10 mfd @ 370vac

It's very possible it needs replacement.
Amazon also carries many caps and can deliver next day.

for example only

 

If indoor blower motor is supposed to be operating when you spin the attached blower (in the correct rotation), it is unlikely the capacitor is the problem. Check for indoor blower motor operation for A/C mode. If it operates, there is a component failing in the HEAT mode circuit. If it doesn't operate, there is a component failing that is common to both modes. There is a schematic on the blower housing.

 

This is an air handler.... not a furnace. It normally runs on one speed.

It may switch to a slower speed in aux mode as that would be electric heat....
but OP said no aux heat needed which means only one speed was used.

 

OP says indoor unit part of heat pump so used for both cooling and heating. So, the indoor blower motor control gets input signals from 2 different circuits.

 

Thanks for the replies!

I have not tried it in air con mode yet. I did try it in emergency heat mode, and the fan still did not come on.

I don't know if the fan is supposed to get energized if I spin it manually, but I had read that the outside unit fan was supposed to be energized if one spins it by hand, when capacitor fails, so I was assuming it was the same with the inside fan. But I do not know.

Another question while we're at it it. Should I discharge the capacitor *before* I remove it, or *after* ?

Also, this cap has three terminals, not two. Is there a necessary sequence to follow in discharging it with the screwdriver method? Lets's say terminal A, terminal B, and terminal C. I would assume I just need to connect A to B with screwdriver, lift screwdriver off, then B to C, lift screwdriver off, then C to A, in three separate discharging maneuvers, and be done with it. Yes?

I am concerned about discharging the capacitor before I remove it, since it is still hooked up to the system, and I definitely don't want to send any current where it does not belong..

Of course I will have shut off the power to the unit before doing any of this.

Thanks

 

I have to correct myself. The capacitor only has two terminals. But it does have 3 wires. I saw a capacitor discharge tool at Harbor Freight. Might get it. only $9.

Should I discharge the cap before removing it, or after?

Thanks guys. This is the only responsive and informative place I have found on the internet, for my particular situation. Thanks again !

 

Hi, just put a screwdriver across the 2 terminals, pull that rubber boot back, if terminals are exposed use the screwdriver if not remove the conductors first if they are insulated, you may get a bit of a spark , that’s normal.
Geo🇺🇸

 

I found the actual number of the cap on the back of it. I just carefully removed the screws and turned it over. It is GE 97F5458 10 micro farad, 370 VAC, 60 Herz. Protected p92f. I googled it, and it is a run capacitor, not a start capacitor. Why would replacing it help * start * the motor?

And what does protected p92f mean ?

Thanks

 

It is a 1986 Trane air handler, if that matters. I am talking about the silver box in the lower left corner with all the wires hooked up to it. Might it have a circuit board inside? Trying to diagnose a 'fan not coming on' condition.

 

That is your control box.
Do you have a volt meter?

 

With the smaller thermostat wires attached there, I would suspect that it is where the circuit board is or where the relays are located.

 

I opened it up and looked inside. A bunch of wires, but also some small flat rectangular electronic pieces with printing on them. Did not see any fuses or capacitors, but I couldn't see everything in there.


Yes, I have a multimeter that reads AC volts. Why? Can I test something ?

 

Easier to keep all posts in one thread.

On that metal box you should see R and C. There should be 24vac there.
You should see R and G. There should be 24vac there.
When you go to fan on or when the air handler should be running.... there should be 0v between R and G.

If you can to test the control..... you can short between R and G. That will bring the motor on.
If it doesn't.... you should at least hear a click from the box.

 

Thanks. I will look at the box tonight for R, C, and G.

I can't remember if the 'fan' position on my thermostat makes the fan come on regardless of the temp. Is it standard for 'fan' position to override temp ?

 

The "fan on" takes precedence and turns the blower on regardless of the mode set.
It does that by connecting R to G.

 

Would connecting R to G involve the contactor?

 

Connecting R to G activates a relay inside of that metal box for just the blower.
A call for cooling activates two things..... R to Y (contactor) and R to G (blower).

 

Thanks for the help, PJmax!

I have some more symptoms to list. If I set the thermostat to 'fan' I get a hum from the box but not from the fan.

Another thing. The transformer on top of the box is always warm.

I looked at the box where the wires go in, and saw R and G, but no C. Two of the letters are covered by wires, so maybe the C is covered up.

If I hook my multimeter probes to R and G I expect to see zero volts? If the system were working normally, I would see 24 volts there ?

If I touch R and G with the probes of the multimeter, isn't that the same as shorting R and G ? Does the multimeter prevent voltage from flowing through ?

 

Correct. That hum is the relay. That is exactly what should happen.
The transformers do operate warm.

Look at the control box..... see the two yellow wires. Those are the Y connections.
One wire goes to the thermostat.... the other goes to the outside condenser.
There should be two wires going outside.... Y and C.
The G terminal will only connect to the thermostat (cable)

If you posted larger pictures I could see I can help you better.

 

Hi,

Thanks for previous replies.

I am still working on diagnosing my 'blower motor not coming on' problem.

I tested the volts on my control box between R and G and got 29 volts, with thermostat set to 'off' and fan set to 'auto', so no call for fan. I THINK this means the windings in the motor have 'shorted out', and I need to replace the motor. Right?

But it spins easily and quietly by hand. The only symptoms of it going bad were a slight vibration and high frequency slight rattling sound, at the air handler which went away if you pressed on the air handler. And also sometimes a very faint odor of hot electronics, only occasionally (alarming, I guess, now that I think of it).

I want to test for voltage at the motor next. I want to test it right at the motor connections, without removing them (they won't come off for me). Can I insert the probes into the red and the purple wire connections at the motor? Do I need to know which one is positive and which one is neg?

I have attached a pic of the control box and of the motor connections.
Slow and steady wins the race.

 

Does the motor hum or show any sign of life?

Spinning the motor only tells you that it is not mechanically bound or that the bearings are good/bad. Most everything else is electrical. The capacitor would be the first thing I check since it's a common culprit.

You can check for voltage at the other end of the motor's wires. It will be AC so no polarity to worry about. You could also use a non-contact voltage tester to get a crude idea if you are careful.

 

Thanks for responding.

No hum from the motor. But there is a hum from the transformer on the control box.

I have replaced the capacitor, which was bad, with new one.

Thanks for the tip about no polarity to worry about since it is ac.

I would test the motor wire voltage at the other end, but unfortunately that would require snapping apart a plastic connector, which might crack. That's why I am intent on testing it at the motor connections, if possible.

But I will check out the plastic connector. Maybe it will come apart without breaking.

The connector I am worried about is just under the big yellow warning sign, and to the left a bit. Should be a piece of cake, but it doesn't want to come apart.


It has the 2 horizontal wires from the motor going into it, purple and red. Would be a perfect place to test. There is a bolt holding a bracket in right next to it. Will take bolt out, maybe the connector will come apart then.

 

I asked that you keep all replies in THIS thread. Having members have to ask questions that were already answered wastes everyone's time.

I was looking for closeup picture of the control box only so that I can see the letters on the board.
You posted XE1000. That is the outside condenser.... not the air handler which you are working on.

You measured voltage from R to G. That means you have 24vac.
When you turn the blower on you hear a hum from the box. That means the relay is turning on.

Measure from the black on the capacitor to the red wire on the motor.
There should be 120vac there when the blower should be running.
I believe the black is common and red and white are speed colors. Looks like red is used.

 

Thanks for the reply, Pjmax. I will keep my future posts inside this thread.

I suppose you are right that the air handler is not a Trane XE1000. It doesn't have a badge on that I have noticed but the model number on the door is a Trane model number. It is 11 years older than my outdoor unit.

Yesterday I was able to get the leads off the fan motor somehow.

Did some more testing with the voltmeter, in various thermostat combinations. I had power to the indoor and outdoor units on. I had both wires off the motor for every test.

Whenever I had the thermostat set to 'fan', I got zero volts between R and G, and 28 volts when I grounded R to the metal box. Always got 28 volts grounding R to the box, no matter what thermostat setting.

When I had the thermostat set to something that would not call for fan, I got 28 volts between R and G.

The above is all good news, I believe, except for always getting zero volts at the motor wires.

I think a good next test would be to jumper R and G and see what happens, as you suggested earlier.
I would hook the wires back onto the motor first, with power off. Then turn power on to indoor and outdoor units. Then set the thermostat to 'fan', then jumper R and G with a paperclip, using thick gloves so I would not get shocked.

Would the jumpering of R and G just bypass any possible problems inside the control box, and send 110 volts out of the back of the control box to the motor?

 

No. You can short R and G which you've done before.
You heard the relay humming when in fan mode.
All you know is that the relay coil is ok. You'd need to still check for 120v to the motor.

 

I have not yet shorted R and G. I only tested the voltage between them. Can I short R and G with the power already on without risking damage to the electronics?

 

I got the connector apart on the wires feeding into the motor, and got a better contact with the probes than I had on the other end of the wires.

When I set the thermostat set to 'auto', I got 21 volts (twenty one) . Was expecting zero. When I moved the thermostat to 'fan', I was expecting 110 volts, but still got 21 volts.

What does that mean ?

I s

 

R and G are the terminals that activate the blower relay.
You can create a short across them at any time.

In "fan on" mode.... there should be close to 0 volts there.
There will be 24v present in "auto" mode until the compressor starts and then it will be 0.

 

Thank you. I am clear now about the R and G . But why am I getting 21 volts going to the *fan motor* ? Why not zero or 120 ?
l
I am testing the 2 wires going to the fan motor, and I only get 21 volts, both in 'fan on' and 'fan off' modes.

 

OK, I went ahead and did it. Set thermostat to off and auto, then went down to the air handler and jumped G and R with a penny.
Heard a click when I touched the penny to the terminals, and another click when I removed the penny.

The click was coming from inside the control box.

The contactor didn't make any sound, or move at all. (Don't know if it is supposed to, anyway)

I had multimeter probes in the wires to the motor, and the voltage was stuck at 21, even when jumping the R and G. Actually, it did move up or down, but just by one volt between jumpered an unjumpered.

What now?

 

The click is the blower relay.
You will not activate the outside contactor until you short R to Y.

Not sure if I addressed this earlier.... most blower doors have a safety switch on them so power is disconnected when the door is open. Make sure that is pushed in if there is one.

Try this for me.... put the thermostat in fan on. That would mean the blower relay is closed.
Clip or touch your black test lead to any ground. Put it somewhere where it will stay connected by
itself so you don't have to hold it. Maybe next to or behind the cap.
Using your red probe.... check the black wire on the cap, red and white on the motor.
Do you get 120v on any of those three ?

If you don't get any voltage on these three points....... turn power off to the air handler.
Short across the cap for 2 seconds to make sure there is no stored charge.
Change your meter from AC volts to OHMS. Leave black where it is.
Try touching the three points. Do any show a low resistance ?

 

I put it in fan mode, and I got 120 volts upstream from the motor, at a connector I took apart. There were 2 wires at the connector, a red and a dark purple. At the red I got zero, at the dark purple I got 120. That was with the black probe on ground. When I tested it my usual way, with red probe in the red wire, and black probe in the dark purple wire, I got 21 again. Good news is I got 120 volts at the dark purple when grounded, right?

I haven't tested at the capacitor yet.

 

The two wires in the pic that are on the motor are red and light purple. The pic makes the light purple wire look white, maybe.

Yes, that is the plug (connector) I was using, in the center bottom of the pic. The left hand side has a dark purple wire and a red wire. The right hand side has 3 wires. I tested the 2 wires on the left hand side with the plug apart.

The dark purple wire looks almost black. There are black wires too. You have to look close. For instance, the capacitor has a black wire, a dark purple wire, and a yellow wire.

I will try to get a clear pic of the schematic for you.

 

this for me.... put the thermostat in fan on. That would mean the blower relay is closed.
Clip or touch your black test lead to any ground. Put it somewhere where it will stay connected by
itself so you don't have to hold it. Maybe next to or behind the cap.
Using your red probe.... check the black wire on the cap, red and white on the motor.
Do you get 120v on any of those three ? >>>

I am ready to test voltage at the capacitor. I'll have power on, in fan mode, will put black wire to ground, will put red probe on the black wire on cap, see if I get voltage. Also will put red probe on red and white wires going to motor. The red and white wires are going to the spade terminals.
Are these speed wires, by any chance? I checked them, when they were off the motor, and got one volt at each wire, with
black probe grounded.

Can I check all three wires at the cap? Don't want to fry anything.

 

Ok.... sorry for the delay. Your blower motor is 240vAC. The black wire is one half of the 240v power and is always live. You will always measure 120vAC on the black wire. The red wire is the other half of the 240v power. You can see it passes thru the F blower relay. Since you are not getting to 240v to the blower motor BUT the relay is working... it would appear the relay contacts are burned. You would need to open that metal box to visually check the relay.









I could not upload resized/labeled pics in your posts so they are all here.

 

No, you will not get 240 volts only measuring at the cap.

Measure red to black at the plug that is normally connected to the one in this picture when the fan is on at the thermostat. (The harness in the picture is not going to have power, the other half with only 2 wires will)

 

I tested for voltage between the red and black (dark purple) wires at the connector that only has 2 wires. I only got 21 volts, both with fan on and fan off. This is with putting red probe into red wire, and black probe into black wire.

 

21 volts is a surprising reading. I would expect 240VAC or 0VAC.
Have you proven 240 volts to the air handler with that meter in your testing?
Are you on AC voltage?

I like to prove that my testing equipment if functioning at the start of each service call.
My meter, meter leads and volt stick will fail one day. ( Especially the Meter leads)

Are you comfortable shutting off power and removing the small panel in the lower left portion of the air handler?

Post a picture of the relay in there. Is it melted?

The diagram shows a double pole single throw relay.
I would measure terminal 1 to terminal 3 for 240 or 0 volts.
I would also measure the low voltage connections blue to green on that relay for 24 or 0 volts.

 

I have not seen 240 Volts anywhere yet. The most I got was 121, and that was only at the dark purple wire of the 2 wire connector, when grounded.
I had the voltmeter set on 700 volts AC, and when I grounded the black probe. I tested between green and red on the board, and got 28 volts. Haven't tested between blue and green yet. If I can't get to the relay, would it help if I tested between blue and green on the panel? It won't hurt anything, right?

I have opened the control box, in the lower left, and can see the relay in there. As far as being melted, there are some sort of blobs on the far bottom end of it that might be melted plastic. I can't get a good look at it, even with flashlight. The way the wires are situated, I will have to
take off all the spade connections behind the faceplate on the control box, then take the 4 screws out holding the box to the unit, then hope I can get the box out far enough to get a look at the relay inside, all without damaging anything, hopefully. Kind of awkward.

I will try to get a pic of the relay where it is now, with just the cover off. Might get lucky.

Someone said the 21 volts might be 'phantom voltage' caused by magnetism. Interesting.

My voltmeter is working fine, I think, because if I leave it on 700 volts ac, I can still get a reading of 28 volts between red and green,