Hi,
I have an outside compressor and a forced hot air furnace setup that's been working great for years... except today when I tried the A/C for the first time.

Today, when I flipped the thermostat over to cool, I heard the compressor kick on, but then I noticed that the blower inside the furnace never did. So, just to be sure that the blower was still functional I kicked on the heat, and the furnace fired up no problem and was blowing heat fine. At least I know the blower itself is working fine.

I tried the A/C a few more times, this time actually down at the furnace, so I could hear the sequence. And the compressor definitely kicks in immediately (I can hear it running), and I can hear the refrigerant coursing through the lines and the A-coil. But the blower seems to start for maybe 1 or 2 seconds, but then just kicks out. I also noticed the light on the control board turn on and then off out the same time that the blower does.

And the compressor seems perfectly willing to stay on, unless I turn it off at the thermostat.

Any ideas?

Thanks for any help,
--Zach

Sounds like your control board is going bad. Does the fan work in the fan on position?

Just tried, and nope it doesn't. Same symptom as before. The control board and blower turn on maybe a second or 2 and then shut off... leaving the compressor running outside.

Any addition tests I should do? Or is it time to pay someone to come and take a look?

What brand furnace do you have?

Do you know here your control board is?

You may be able to put the cooling wire on eac and see if it works sometimes this has a different relay.

One other though... Even though this furnace and blower work fine for heat, you're thinking that something is messed on the control board related to A/C only?

Are there any diagnostics I can do to rule in/out the control board for sure?

For the record, the furnace is a Coleman Evcon, model # G9D10014UPC11C.

Thanks,
--Zach

Wow, you're quick... by the time I got back downstairs and back again to write my last follow-up, you have already hit me with 3 questions:

1) Cooling wire to EAC... no problem moving the wire. Which color should I be looking for? Or which contact?

2) yep, I know where the control board is. The panel covering has a nice lockout switch that I keep forgetting about!

And I mentioned the model # in the last post. Is that the info you were looking for?

Well let me think, is this a new furnace? Like with in 5 yrs old?

On the control board, there should be a wire that says heat probably red, and a wire that is on the cool terminal probably black

Your unit will probably have a 4 speed fan motor

Yep... pretty new furnace. 5 years sounds about right.

OK, I see the black wire on the cool terminal. It's a spaded terminal, not a screw terminal, if that helps...

I also see the EAC terminal. Want me to move the black terminal from cool to EAC? Leave the each hanging for now?

For your info, on the upper terminal block where the white wires are, there is no white wire on the EAC terminal there.

Also, what exactly is EAC? Electronic air cleaner? Maybe?

Sorry little typo in the last email... should have read "leave EAC hanging for now?"

Is there a wire on the eac now? And yes it stands for electric air cleaner

There is a black wire on the EAC terminal now (near the cool terminal), just not a white wire on the other EAC terminal.

Can you trace it and see where it goes? Before we switch them I do not want you to mess anything up. Do you have a air cleaner?

I'll go try and trace it now, but no I don't have an air cleaner... I have A/C and a humidifier, but the only thing cleaning my air is the regular inline paper filter.

OK well if it does not go to anything then put the cool on the eac and leave the eac hang and try it

OK, traced the EAC wire and it just dead-ends, with nice crimped terminator on it... nothing on it.

Should I try it? Switch the cool with the EAC? And give it a whirl?

Yep

Holy crap... that worked like a charm!! The blower kicked in and off it went!

Is this a viable long term solution? Or should I look into getting a new control board?

Any suggestions on where to find something like that? Grainger? I'm pretty comfortable actually changing it, if I can get my hands on one.

Thanks a ton!!

This will work for you intill you are able to get a new board. The really that runs the eac will not carry as many amps and it will soon start doing what the cooling relay is doing now. Hard to say it may lasta day it may last 2 yrs. I do it when I am on service calls sometimes just to get the homeowner cool air till I got a new board for them.

Grainger may have it.

OK, I feel like a fool... when I said it worked, I was completely wrong. I had left the thermostat on "off", not heat or cool. So, when I flipped on the power switch after moving the cool to eac, the blower kicked on... doing nothing but recirculating air. But when I put the thermo back to cool and turned the it to on, it did the same thing... compressor kicked on and then the on/off thing the blower was doing before.

No change from move from EAC to cool.

Got any other tricks up your sleeve??

One other thing I noticed ( and it may not matter), but the cool plug is also jumped to "heat-hi".

This is so both heat and cool are on high speed, should not matter the realys are separated

I am about 85% sure you are going to need a new board, but for the time being if the t-stat is controlling the outdoor unit fine you can wire the fan so it runs all the time.

OK, that sounds promising... How would I do that?

Well that black wire you hooked to eac. You can splice it with the black wire going to L1, other then the board I am not thinking of anything that would be causing our symptoms. And you say the fan will run all day long in the heat cycle?

The heat side of the furnace was working fine, even 2 days ago. I know it was on for a good hour Thursday morning.

So, I'm little confused by what you mean by L1? I have a contact labeled "Line"... is that the one?

Yes that's the one, or you can just wire it right to the main power where it comes in to the black wire.

OK, thanks for the info. I'm not sure what I'm going to do.

I found the local distributor, so I'm going to see if I can get the controller tomorrow.

And, here's the kicker: I put everything back, so that I'd know where everything was when I replace the controller. Just for fun, I tried it one more time and it actually all turned on! What? Yep, I'm getting nice cool air blowing through my house.

I must have tried this 20 times today, especially with all the help you've been giving me. And then boom, it starts working...

Maybe some carbon buildup? Maybe a stuck relay? Maybe a bad connection? Not something that I can rely on, for sure.

I'm going to keep a close eye on it, and maybe get the controller just in case...

Thanks for all the help.

--Zach

Glad it is working for you, there is a chance it was just a lose connection I get about 1 of those a week. Good luck let me now how it turns out for you.