HVAC Split Unit Heat works fine, A/C compressor on fan off

Joshdta · Jun 14, 2009, 01:01 PM

Sounds like your fan center relay has went bad. Pull the little white botton on the fan limit intill you get one and you should have ac the rest of the weekend.

p2pcoach · Jun 14, 2009, 04:36 PM

Thank for the fast reply! I'll try that. Here is the accurate link to the pictures. Picasa Web Albums - P2PCoach - D4|\/| Furnace

Joshdta · Jun 15, 2009, 04:36 AM

Well from your pictures I see you donn't have a manual fan on botton on the limit. This could also be your t-stat. Jump from are to g at the stat and see if the fan runs

p2pcoach · Jun 15, 2009, 06:54 AM

I tried jumping the are (Rh & Rc jumpered) & G terminals (at the stat) and the fan did not come on. That's the part I am having the hardest time understanding. When I turn the dial (clockwise) on the fan limit (at the furnace) the fan comes on, and then goes off as soon as I let off.

p2pcoach · Jun 15, 2009, 06:58 AM

If I were to pull off all of the wires, and put them back on, what is the best way, do you suppose to wire it? I have 4 from the stat,
Red,Green,White,Blue;
2 from the A/c - Red and White.
And 2 from the Gas Valve - Red and white

Which wire would go to which terminal?

hvac1000 · Jun 15, 2009, 02:37 PM

There should be a relay in that black fan center.

hvac1000 · Jun 15, 2009, 02:39 PM

PS the dial you are turning is only designed to work in the heat mode not in AC. Stop turning the dial manually or you will stretch the BI-METAL and that will be the next item you will be replacing in the heating season.

p2pcoach · Jun 15, 2009, 04:29 PM

Thanks. There is a relay, and I hear it engage (loud click) when I energize the circuit. Is there supposed to be something else?

I would be surprised if something were missing, as everything was working fine last fall when we still used a/c, and then all through the winter. We switched the stat to heat, everything okay all through the winter. When we went to switch the stat to cool, this spring, that's when stuff stopped working. Then the wires got pulled off the contactor. And here we are....
Sorry I was unaware of the fan limit spring stretching.

Is it possible that there is another relay in the compressor that is bad - does it possibly control the blower inside? Just a question.

If that relay that engages when the circuit is energized, is it possible that the contactor block is bad? Maybe the wires in back are wired incorrectly....those haven't changed since last year.

Is there a way to bypass the contactor block to temporarily get a/c until this is resolved? My wife is going crazy, and I insist on fixing this, as it seems simple, yet not easy.

hvac1000 · Jun 15, 2009, 08:35 PM

I pointed you in the correct direction to start your search for your unit problem which is in the picture of yours I posted back to you. You seem to have a low voltage problem or a relay that is defective. Just because something clicks does not mean it is working corectly. Thake your meter and check that relay for proper operation. The indoor unit HAS to have a relay to control the blower motor in the A/C mode. This is where you need to start. I agree your problem is simple in nature but to the uninformed it could be a complex issue and difficult to understand.

There is a generic wiring diagram for fan control centers in the link below. It might not look like yours but they are all just about the same. Good luck with your adventure.

http://www.white-rodgers.com/wrdhom/.../0037-5786.pdf

HVAC Split Unit Heat works fine, A/C compressor on fan off

Add your answer here.

Check out some similar questions!