Outside units stops, inside unit doesn't

[Bane01]

We are having issues with our heat pump. I apologize that I don't have the model # at this time but I will update when I get it. I know that it is a Coleman unit, 12 seer and was installed in 2002. we called the repair man out when we noticed that shortly after we switched to AC this spring I came home to find the interior blower fan was still running but the outside unit was off. The repairman replace the outside fan based upon the fact that it was retaining water and didn't seem to be turning smoothly. He also checked the freon levels and all the voltages and capacitors.

It worked well for about a month. We hoped that had cured the problem, but it didn't. We called him to say that it still wasn't working right. He came out and checked the voltages and capacitors and all checked out fine. all he could say was to keep calling him if it happened and maybe he could find something eventually. I have researched everywhere and am at my wits end.

The unit comes on and runs as it should for the first while (normally 10 - 20 minutes or so) then the outside unit will stop and the inside unit will run indefinitely. when this happens we can turn up the thermostat until the interior blower goes off. It seems to do it more if we turn the thermostat down until it comes on than if we let it come on by itself. It also seems to do it more when we try turning it down to ~ 75 - 76 degrees than if we leave it at 78 - 80 degrees.

We have tried resetting the breakers and turning the unit off, etc. This doesn't seem to help. I don't know what else to try. Any suggestions or troubleshooting tips are welcome. At this point we don't know whether it is the outside unit, the inside unit or the thermostat!

[Robert]

Trace blower cooling wires back to most likely a molex connector plug and then onto a fan relay or control board.

See if relay or board are losing signal from t-stat when required and then if so, is the relay or board closing the contacts or circuit to the blower.


Not real hard to find if he's experienced in troubleshooting.


Just need to find where power is getting through when it shouldn't.


Thanks,
Robert

[Bane01]

Thanks Robert - are you referring to the fan relay in the inside blower unit and the control board outside or are both pieces inside? If we are having an issue as you describe why would the blower fan cut off when the thermostat is turned up?

Can you suggest where to get manuals for my inside and outside unit if I have model numbers?

Thanks again!

[Robert]

Hi,

They will be in the furnace, one or the other, not both. Either a fan relay or a control board with a small fan relay on the board.


When you turn t-stat up, it turns off signal to relay or board. Sometimes after a while not being energized, the contacts will cool and release.

That's just a possibility, will need entire cooling circuit tested to know what problem is for sure.


You can get the manuals from Mark through this website :


http://www.hvacmanuals.com/




Thanks,
Robert

[Bane01]

sorry, this may sound stupid, but you said "in the furnace" - do you mean the inside unit? we have a heat pump, not a furnace. like i said that may be a dumb thing to say and i am sure my ignorance is showing! LOL

[Robert]

Hi,

The heat pump is the outside unit. The inside unit is either a furnace for back up heat to the heat pump (usually needed) or a air handler unit , both with the inside a-coil.


They would be in the controls area or a/c control box in the furnace or air handler unit.


Thanks,
Robert

[Bane01]

i found the model number - it is EB12B. when i searched for the manual I got this as a result -
http://www.nordyne.com/Literature/359a.pdf

is there a relationship between coleman and nordyne?

[Bane01]

also, i see a lot of posts here for this unit saying it is a relay or a sequencer, could that be our problem? maybe a "sticky" relay. where it works sometimes but not always?

[Robert]

Hi,

Coleman and Nordyne are two separate manufacturers. Your furnace has a fan relay in the controls area.



Thanks,
Robert

[Bane01]

okay - we may be able to trooubleshoot some this weekend. what really seems strange is that it seems to work okay in the morning and in the evening when it is a bit cooler. during the hot part of the day is when it starts messing up. the outside unit will run for ~ 10 minutes or so and then it cuts off, but the inside is still going. Is there anything that explains why it works this way - or rather doesn't work!?! I really appreciate your help and advice.

[Robert]

Defective parts, old unit, dirty unit, low on refrigerant charge. Too many variables that can encompass those symptoms.



Thanks,
Robert

[Bane01]

okay - you mentioned dirty unit. We took a good look at the interior coil last night and saw that it does have dust/hair/etc. on the coils. We cleaned off the right hand side with a soft brush but the left-hand side is hard to get to because of where the coolant lines come up in the front. Do you think this could be the root of the problem? Should we try getting this cleaned up better before we dig any further? Any suggestions on how to get in around the lines and avoid the sharp metal edges (where top filter goes)?

[Robert]

Here ya go:

http://www.mobilehomerepair.com/hvac/ar ... ioner.html




Thanks,
Robert

[Bane01]

after we cleaned what we could yesterday on the A coil the unit only messed up once. we are going to get a flat toilet brush today and try to clean it some more. does it sound like we are on the right path?

just out of curiousity, does the compressor have a safeguard that would shut it down if the coolant becomes liquid? could that be why the outside unit is cutting off if the inside isn't breathing?

[Bane01]

okay one more piece of info on this. we came in from an errand and the inside unit was running (don't know for how long) and the outside wasn't. i was going to turn the thermostat up to cut off the blower and then the outside unit kicked in. is it supposed to do this? I didn't think it worked that way. does this mean anything? again, i do appreciate the help!