I have two identical air-handlers (one for upstairs and one for downstairs) and one of them is not powering on.

Per my HomeDepot 1-2-3 DIY book :-) it says to stick a multimeter on the ohms setting and check the reading when touching the C and G terminals on the relay.

On the good air-handler, the reading goes from 1 to 0 as expected. On the bad one the reading goes from 1 to 1.5. The book says to replace the relay if it's not 0.

It seems like a simple swap out but I have no idea on the PN or a reputable place to buy.

I'm not sure on the make of the air-handler, but the model number on the system is: F2RP024N06B. The outside compressor has a Fraser-Johnston badge on it, so I assume the inside unit is the same brand.

Do you think I'm on the right track? Any idea how to get the PN to replace the relay? Where's a recommended place to shop?

Thanks

 

Post pictures of the component to get a better chance at identifying it.

 

It would be much better to switch your meter to volts and check for 24 volts from G to C at the air handler when you have the thermostat turned on and either calling for cooling or you have the FAN switch on the thermostat tuned to the ON position. An ohms check is going to misleading. What kind of heat do you have?

 

I'll see if my camera phone does a good enough job... but in the meantime, I found the manual and it describes it as the "control board" rather than the relay.

I should have described it better to begin with - it's a circuit board about 5" x 3" with the terminals for the wiring that goes to the thermostat.

 

Maybe it's time for a new book.

To test blower operation, try connecting a jumper from the "r" terminal to the "g" terminal on the circuit board. If working correctly, the blower should turn on.

 

pop off the thermostatcover and depending on the thermostat you have either unscrew the front or pop off the front and see where the wires connect. Jump
(24V power ) to G to start the fan, or to Y to start the AC, or to W to start the heat...

 

so do you have 24 volts from G to C at the control board terminals?

 

It's just too dark to get a decent picture - but I no longer think the control board is my problem.

 

You were absolutely correct - the ohms reading was spurious. I have the thermostat set to "system off/fan on" and my multimeter set to the 200 volts setting - and I get nothing whatsoever from touching the probes to the G and C terminals.

I checked the breaker in the basement and it's set to ON so there must be something inbetween causing the problem.

Is this something a layman can troubleshoot? I can follow directions but have no experience.

 

thanks everyone for the advice BTW - even if I didn't respond directly it's definitely gladly received.

 

my bad
I neglected to ask you if the outdoor unit is coming on when you set the thermostat for cooling. At the AH check for 24 volts from R to C terminals.
What kind of heat do you have?

 

nope - the outdoor unit does not come on when the thermostat is set for cooling. Although I can go outside, remove the cover, press a button and have it spin.

R to C terminals also show no response on the multimeter

As for the type of heat, the manual says "single piece air-handler, heat pump"

I do seem to remember that the seller mentioned something about 2-stage heat. Not sure how to verify though

 

R is 24 volt hot..C is common[ground] G is fan [NOT ground]. Zero volts R to C indicates no 24 volts. Make sure you have full volts to unit[120v]. look at the board for a fuse. Shut unit power off before reaching in to pull fuse.

 

If it's a heat pump, the air handler should have a 240 v power supply. Additionally, you most likely have electric heat strips as the second stage of heat.

 

this needs to be addressed. It doesnt work without line voltage power... Test this first.
If you have line voltage, This means you have to test for secondary voltage, usually a blue and yellow wire..but thats not written in stone, it is however written on the side of the transformer which two wires are low voltage or secondary... It should be 24-30Volts approx... Transformers usually protect the secondary side with a fuseable link of some sort. A glass buss fuse or the car type on a circuit board, or in a black snap apart inline fuse. If not when you buy one ask for a 50VA transformer with circuit breaker, instead of the usual 40VA without. Then if there is a short in the system you won't have to buy another transformer, otherwise you will. Its likely the transformer is dead... TEST IT, R to C=24 volts approx...

 

thanks... I think this is all beyond my capabilities though. Sticking multimeter probes onto live systems makes me a little nervous :-)

 

At this point I would say to call in a tech. If you are not comfortable using the multimeter, that alone can invite an accident.

Fraser Johnston is an off shoot brand of York.

Take 1 Fraser Johnstone, 1 Luxaire, 1 Coleman-Evcon, and 1 cheap York. All the same packaging just a differant brnd name sticker on the box for the installer to stick on the unit.