AC BLOWER IS NOT COMING ON, COMPRESSOR OUTSIDE DOES COME ON. Got 28v A.C. at all the thermostat wires except one (as i remember).. does anyone know which wires to jump to make the fan come on without the thermostat. Tried fan on switch (auto or manual) and that does not work.. i'm just trying to make sure the thermostat is not the problem. thanks.

ALSO, I took the cover off the inside unit, was able to spin the squirrel cage fan easily (not stuck, thinking probably not the capacitor ). I hear a humming noise, took the other cover off (covering the elements and sequencing relays ), could not find anything like a control board (must be old style unit), but did tap on what looks like a relay (A) that has at least one probably 10 gauge wire going to the fan/blower motor, the humming seemed to lessen, more tapping made it louder again? (bad relay , maybe its stuck in the off position?)
History: the unit has worked well many years; yesterday i noticed that the fan did not seem to come on immediately, so I turned the thermostat off then on, it came on, I was thinking "ok, its just a normal hiccup".. later in the morning i heard some type of strange noise, traced it outside to outside ac unit, it was all iced up, turned t-stat off, the outside unit and the outside noise quit: when I was turning off the t-stat, I noticed the temp setting was stuck at just below the room temp (Hunter electronic thermostat brand). I thought that is strange. I'm thinking maybe if the relay inside the inside unit (A) were stuck off, it could it prevent the thermostat from ever progressing in the program (its set to go to a higher temp after midnite)?
Any advice especially on how to test the fan itself , and the relay, would be nice. I would think the transformer inside would be ok if its putting out 28v A.C. (not D.C), am I right?

 

One more thing: I touched the relay (A) and it did seem hot but not so hot that it would burn my finger. Is that normal?

 

If you want to bypass the thermostat to rule it out as a possible cause, jumper terminals R or RC (they may be connected together) to terminal G. Conversely, if you have a voltmeter and you want to check voltages, you should measure ~24VAC between terminals G and C (common). The 24VAC present on the G terminal signals the air handler to turn on the blower.

On older, non electronic systems, a relay is often used to control the blower motor. The wire connected to the G terminal is connected to the control (low voltage) side of a relay. When 24VAC appears on the control line, it energizes the relay which turns on the blower motor. Relays normally don't get hot, so if you're sure that what you're feeling is a relay, I'd be suspicious that something is wrong. You would have to trace the wiring to see if the output (line voltage) side of the relay goes to the blower motor. Be very careful if working with the power turned on, as there are lethal voltages present.

 

``I checked the only 2 wires from the relays to the fan motor (disregarding 3 wires from capacitor to fan motor)... infinity reading on ohm meter.. Took relay out , it checked good with 28 vac on the coil (pins 3 & 1 Green wire); coinducting well thru the pins 4, and 2 (2 is the one that goes to the fan motor) it also goes splits off to a tri-stack sequencer that seems to be thermally activated. (probably to make the fan run longer than the heater to increase efficiency and enhance safetly.
So if only 2 wires from control section to fan motor show infinity even when motor is rotated by hand while testing.. doesn't that indicate bad motor.. wonder how I can find proper replacement, I don't even have the model # of the FREIDRich AC/Heat unit ?
Transformer seems ok, Outside unit fires up when asked to, just the fan motor doesn't run and even when relay is tripped and fan is rotated by hand , it still doesn't take off, fan motor only 2 wires from control section to fan motor show infinity on ohm meter.. DOES this say motor is bad? Wonder how I can get model # of motor or Freidrich unit?
Yes I jumped R and G,, relay sounded and felt like it tripped but no fan movement.

 

Instead of checking for resistance to the blower motor ........ check for voltage. It also sounds like maybe a sequencer relay is getting hot and that may be an additional issue.

Look around the air handler....there IS a model number plate on it somewhere.

 

GOOD /BAD news: With the R-G jumper connected I saw (Tstat* not connected) 240vac at the only 2 fan wires coming from control section (one of the fan wires is spliced/connected to 2 or 3 other wires coming out of the fan motor itself). THIS APPEARS NORMAL except that the FAN still does not turn, I tried rotating the squirrel cage both directions with wood stick with 240vac on the 2 wires, but no luck. Grounding wire to motor registers correct voltage when tested from one phase to the motor ground wire and the motor housing itself. Bad motor?
I "THINK" I may have the model # as I found an installation pamphlet that someone hand-wrote "Friedrich, Model # EF20-10D, Serial # number 52538 , FAN 1/3 HP 240v single phase" in the pamphlet I found on page 13 (which has a wiring schematic). Nowhere on the pamphlet does it say officially "Friedrich" only what someone hand wrote, but it "seems" to be the right one "maybe". There is only 105vac with NO R-G jumper connected at the only 2 fan wires coming from the relay control sequencer section, Tstat disconnected, (pamphlet officially says the fan motor should be standard 230vac 240vac on page 11) ;
The FAN also does NOT turn when rotated with wood stick at the 105vac (I don't think I should expect it to, just info). I checked the relay and it did check out good on the bench, reinstalled it before checking for the voltages listed above, What does this sound like?
The strange part is that the Tstat is not even connected (took it off the wall) and no jumper wire was used from R to G when voltage 105vac was found at the fan motor.
In all cases the outside unit (thankfully remained off I think because the tstat was removed).
I may check some splices mentioned above where the 15 years ago installer probably twisted some wires together, but not holding out much hope that the motor is still good at this point.
How to make sure motor is defective, can it be fixed by putting new brushes? If so where can I get the brushes, or where to get new motor on the cheap. $$, Thanks ahead of time for any advice on this.

*Tstat = Thermostat (Hunter brand electronic programmable).

 

Bob, new info on Friedrich fan not coming on problem, thaniks for any help. (just in case you were not notified via email). http://www.doityourself.com/forum/ai...ml#post2154671

 

Can you easily get to the motor? On the old furnace I had, the whole blower assembly (squirrel cage & motor) slid out. With the new furnace I have now (York 95% efficiency modulating gas furnace), it's very difficult to get to the blower assembly.

If you can easily gain access to the motor, you can check it to see if there are any brushes. However, I doubt that you'll find any. How many wires does the motor have, and is there voltage at the motor? There should be a label on the motor giving the voltage, amperage, HP, and rotation speed. Once you have the motor specs, you can try to find a replacement motor, if it appears that the motor is bad.

 

It is extremely hard to follow what you are doing. Most motors don't have a ground wire included with their connection wires.

No idea how you would be reading 105vac but that is not correct.

What you left as a possible model number is not correct.

Is there a part number on the motor ?
Can you shoot some photos of the wiring ?

I mentioned earlier a sequencer issue. A sequencer does not care about the red to green wiring connection. If the sequencer has been activated.... IT calls for the fan.

 

Just to set the record straight: I did not do any of this, it was here when I bought the house, the furnace and ac worked fine for at least 10 years but that doesn't mean it was wired correctly in the beginning either). How can I post pictures or wiring diagrams? .. the old pamphlet may not go to this furnace but maybe it does too, in either case its old faded, and is degraded/ brittle with some holes in some areas, so I doubt I can fax or scan it very easily with my scanner.. I'm not even sure I can photograph it very well since its wiring diagram is so small .

Yes the fan motor is easy to get to. I can easily unscrew the mounting bolts (3) but I don't know how to reach the drive shaft unless I take the whole squirrel cage assy out first? (or do we get lucky and the drive shaft just slips into a square hole in the cage? I can see numbers stamped on the FAN MOTOR and printed on the very axis plate itself on the fan motor (some of it is obliterated with age, but can read partially as follows:
" .............?...... Electric co , ...?... Volt 230, ....MP 37..., ..?..P 1/3 , L72 8 , ....?... PM 1050/3 sp, ... Air Over Cont, Thermally Protected. "
On the WIRING: There was an error in the earlier post because someone had taped and doubled over 2 wires to one of the feed wires and it looked like 4-5 wires spliced, but I took off the tape and found that there was no connections there at all, they were just using the feed wire to keep the other non-used wires out of the way.
So the wiring is as follows.. (I don't know how to post pictures on this site)
Again there are only 2 wires coming to fan motor from control/relay/sequencers area (only 2), one (black) comes directly from one side of the incoming AC from the breaker box and goes to one side of the capacitor (which is probably wrong but also explains why there is 105vac when R-G is not jumped and tstat is out, FYI: I did not do any of this, it was here when I bought the house, the furnace and ac worked fine for at least 10 years but that doesn't mean it was wired correctly in the beginning either). The capacitor has only 2 terminals (normal) and the 2 capacitor wires go into the fan motor, the black one is on the same pin as the feed wire described above.
The other of the only 2 feed wires from the control area goes directly into the fan motor, this wire comes from the relay pin 2 (the relay still seems to heat up when R-G is jumped for awhile , maybe that's normal since perhaps the manufacturer presumed the fan should not be on for that long between heat/ac cycles? It gets almost too hot to touch but It is touchable without pain). So that's it really simple, one feed from fuse box to capacitor live all the time evidently when breaker is on, the other from the relay and also taps off pin2 to the tri-level sequencer.

THE FAN MOTOR : I'm thinking this is a 5 speed fan motor and only 2 speeds are used if that.
Additionally the transformer appears to stay on at all times whether tstat is connected or not, maybe that's normal. The 105 vac across the 2 FAN feed wires (from control area) does seem strange, but that's what I'm reading, checked that 3 times, but as said it also makes some sense since the one feed is live all the time the breaker is on as it ties directly into a very big gauge wire coming from fuse box. The 240vac on the 2 fan wires is also for real when the R-G jumper is used, rechecked that as well, and still the FAN does NOT turn.. even when sq cage is rotated with a wooden stick to help it start , just in case to make sure the capacitor is not the problem.

(There is an additional ground wire that simply makes sure the blower motor is grounded to the rest of the furnace housing, this wire does not go anywhere close to the control section but only bolts to frame of furnace housing and the motor to insure good connection thru for safety grounding reasons I would think)

 

From the information you were able to get off the motor label, I'm guessing that it's a 230V, 1/3HP, 1050RPM, 3 speed motor. It appears from what you were able to determine, that the motor is getting voltage. While I don't know if this is the problem or not, you could try replacing the capacitor, as it's not very expensive. Alternatively, if you have a multimeter, you could do a crude test of the capacitor.

Remove the wires from the capacitor and discharge it with a screwdriver (short between the terminals). With the ohmmeter set to a high resistance scale, connect the leads to the capacitor terminals. Leave the meter attached for 30 seconds. Disconnect the meter and reconnect with the leads reversed. If the capacitor is working, you should see a momentary movement of the meter. If nothing happens, then the capacitor is likely bad.

 

Hey bob, thanks for the capacitor testing info.. (neat trick ! ) ... I'll do it..
But here is something else: Presuming the capacitor is ok: COULD I simply use one of the 2 un-used wires from the fan motor, they both show continuity (power off of course) to the other black-blue/white feed wire, but the one that IS connected shows no continuity at all (infinity). When testing from the black-blue/white feed and the the other feed, its showing infinity, The other 2 are showing 4-7 ohms as said between same black - blue/white feed wire that connects to relay and sequencer.
I would think the other 2 wires are for other lower or higher speeds or am I wrong? the one connected that has no continuity thru the motor to other feed wire, is Yellow/white striped, this is the live wire that ties directly to the fuse box and goes straight into motor (error on this one earlier?).
The other feed wire is black where it taps into capacitor, and then changes color (spliced) in the control relay control area to blue/white and this one also goes to the sequencer top level.
The black capacitor wire is on the same pin as the black-blue/white feed wire above , the 2 capacitor wires go into the fan motor.

The fan motor is 5 1/2" diameter, about 6" from center (Radius) of motor to motor mounts (3 mounts, all about 12 diameter across the squirrel cage), and the squirrel cage opening is about 8 1/2" diameter.
Could it be that simple, just use one of the other speeds that are unused by disconnecting the yellow/white live feed and connecting one of the other 2 un-used wires instead? I won't try it until I get your opinion, thanks.
I have not yet changed any of the original wiring at all in any way.

 

You could try changing to one of the other wires to see if the motor starts. I can't guarantee that they are for the other two speeds, however I suspect that they are. However, one thing to keep in mind is that even if the motor runs when using one of the other wires, the speed will be wrong. My guess is that the other two leads are the slower speeds. As you are no doubt aware, the faster the motor spins, the more air it moves. The air volume (speed) must be matched to the heat or cooling capacity. If the fan runs slower, it will move less air, and you run the risk of the evaporator coil freezing up, as well as reduced cooling (colder air, but less of it). While not optimum, it would be better to have the blower run too fast than too slow.

 

No....it's not that simple. The white wire is usually the neutral or one of the main supply leads in case of 240v. If that wire shows no connection then the motor is bad. Problem could be.... defective winding or thermal overload open.

 

Actually it would probably be better to try the higher ohms wire first just to be safe that its not too fast too quick. thanks for all your advice. Prob going to get new motor and just be done with it. I'm pretty sure the motor is the problem by now I think... thanks again.

 

It did turn out the motor was bad, it was replaced and now is working fine. I think some of these old motors are more difficult to deal with, The wiring on the new one was much easier, as it had 2 separate capacitor wires, and also had 2 separate reversing wires.
Thanks to all for your help ! YouTube has alot of videos, that a person can try to see how their problems would play out.
In hindsight simply checking the ohms on all wires such as common, (white maybe), and black , blue , red, (most times these seem to be hi, med and low speeds).. if any of these have no resistance, the motor is bad, (hi speed to white common should be about 39 ohms as I remember, white to the other speeds (blue, red, ) should be higher ohms like 44, and maybe 54 ohmns). also check ohms to motor housing for each of the main wires, common white to motor housing, blue to motor housing and red to motor housing, to see if there is a direct short (0 ohms here would be bad indicating a direct "short" circuit, infinity would be good).