Short Cycle on Coleman Furnace - Help!

[Frank55]

Greeting Forumerions,

I'm experiencing a very short cycle ( a minute or so) on a Coleman # 8631 furnace.

Any assistance would be greatly appreciated.

Cheers,
Frank

[Robert]

Hi,

Need complete model number and more detail of problem.



Thanks,
Robert

[Frank55]

Mornin' Robert,

Hi,

Need complete model number and more detail of problem.

Thanks,
Robert

Hmmm . . . I thought that was the "exact" model number; I'll get that in short order; in the mean time I'll start from the beginning:

Last winter is when we noticed the furnace would only run for short bursts, frequently shutting off.

This year, our neighbor had our utility company (PG & E) come and check her furnace, and my beloved wife thought that would be a good idea for us as well; being one who likes to keep my wife happy, I whole-heartily agreed!

When the tech came out he noticed that one of the orifices was was clogged (spider web I think); he cleaned it out and we fired it up, and he left. He basically didn't check anything else (beyond perhaps a visual inspection."

The unit seemed to be working OK, but in all honesty I wasn't paying a whole lot of attention since I assumed he corrected the problem. After realizing the unit was "still" doing "short cycles" we then installed a new filter; my wife picked it up and it was one of those super-duper hepa filters--no noticeable change.

Giving it some thought, it dawned on me that this filter didn't have the same "flow-through" as the cheapies we have previously used, so I went and picked up the same ones we had always used and put one of those back in, and it made a difference for a short time. The fan stayed on for between 3 and 5 minutes, opposed to the 1 minute it was doing before and now again.

Aside from replacing the filter, the furnace has never been worked on since we've owned the coach (over 13 years). The fan has never been serviced, oiled or anything.

Separately, I can hear the relay click when the thermostat is turned up, and the unit lights, and it does keep the temperature, which we keep at 72°; the fan just does these short cycles to get there, opposed to staying on like it used to until it reached the proper temperature.

I'm a "hands on guy" and have no problem getting into the unit; I just want to proceed in systematic order to eliminate possible problems.

I'll get the exact model number here shortly.

Thanks in advance for your assistance! Yudaman!

Cheers,
Frank

[Robert]

Hi Frank,


Does the motor feel hot when it shuts off ?

Could be the motor going out, fan switch, control board for most likely.


Thanks,
Robert

[Frank55]

Mornin' Robert,

Hi Frank,


Does the motor feel hot when it shuts off ?

Could be the motor going out, fan switch, control board for most likely.

Thanks,
Robert

Personally, I was leaning towards the blower motor (I'll check and see if it gets hot); I still haven't gotten back there and got the exact model number (got busy). I was thinking about pulling the blower out and cleaning and oiling it to see if that makes any difference . . . your thoughts?

Thanks,
Frank

[Robert]

Hi Frank,

That would be a good starting point:

http://www.mobilehomerepair.com/article ... lower.html


Thanks,
Robert

[Frank55]

Afternoon Robert,

Hi,

Need complete model number and more detail of problem.

Thanks,
Robert

OK . . . I have pulled the blower out; it's pretty funky; however, nothing smelled burn't, or like it overheated etc., I'm going to clean and oil the motor, and clean the fins on the fan itself, and see what happens.

I double checked the model no. and it was "8631." Along side the model no., was the series no.: "776"

Frank

[Robert]

Hi Frank,

8631-776 is complete model number for future reference. Let me know if cleaning helps any.


Thanks,
Robert

[Frank55]

Hi Robert,

Hi Frank,

8631-776 is complete model number for future reference. Let me know if cleaning helps any.


Thanks,
Robert

Still having problems pulling the motor off of the squirrel cage (it's frozen).

Can you tell me the correct motor (and price) needed with that model no.? I haven't seen any identification on the motor yet, as it is still in the squirrel cage; however, I haven't given up yet; hopefully I'll have it out today.

Once thoroughly cleaned, I'm going to reinstall it and see if that does anything (as previously mentioned); if it solves the problem--great! If it improves it (somewhat) then I'll feel that replacing the motor is the best course of action.

That said, if you can provide me with the motor info, I'll be ready to go if that's what needs to happen.

Cheers,
Frank

[Robert]

Hi Frank,

Will get motor info in a few. Do you have heat only or heat and a/c ? may need shaft diameter and length and motor diameter and length as well as hp and rpm of motor. Can usually place 2X4 against shaft and tap motor loose.


Best way and quickest though is go to supply house and get wheel hub puller to remove it.


Or, take it to motor shop and let them remove it for minimal cost or sometimes free.




Thanks,
Robert

[Frank55]

Hi Robert,

Hi Frank,

Will get motor info in a few. Do you have heat only or heat and a/c ? may need shaft diameter and length and motor diameter and length as well as hp and rpm of motor. Can usually place 2X4 against shaft and tap motor loose.

Best way and quickest though is go to supply house and get wheel hub puller to remove it.

Or, take it to motor shop and let them remove it for minimal cost or sometimes free.


Thanks,
Robert

Got motor off; I was able to tap shaft up until it was "flush" with fan shaft opening; however from there it was "stuck" . . . even using my puller it wouldn't budge it.

I ended up pushing it back where it was and filing the edge smooth (it had a slight ridge on it) . . . that did the trick!

With the motor out I can now see some identification info on it, which I will record before putting it back together.

More later . . .

Cheers,
Frank

[Frank55]

Good Day Robert,

Hi Robert,

Hi Frank,

Will get motor info in a few. Do you have heat only or heat and a/c ? may need shaft diameter and length and motor diameter and length as well as hp and rpm of motor. Can usually place 2X4 against shaft and tap motor loose.

Best way and quickest though is go to supply house and get wheel hub puller to remove it.

Or, take it to motor shop and let them remove it for minimal cost or sometimes free.


Thanks,
Robert

Got motor off; I was able to tap shaft up until it was "flush" with fan shaft opening; however from there it was "stuck" . . . even using my puller it wouldn't budge it.

I ended up pushing it back where it was and filing the edge smooth (it had a slight ridge on it) . . . that did the trick!

With the motor out I can now see some identification info on it, which I will record before putting it back together.

More later . . .

Cheers,
Frank

OK . . . I re-assembled everything, now nice and shiny-clean, (and oiled); reinstalled the motor/squirrel cage; set the thermostat to 80° (room temp was at 72° via an electric heater); the furnace lit properly, a couple of minutes later the fan came on (could be me but didn't seem to be workin' quite as hard or as loud), ran for 2-3 minutes max, then shut off; furnace stayed lit; about a minute went by and the fan came on and repeated the process; this went on until the unit reached the set temp on the thermostat (about 12 to 15 minutes).

Although the unit doesn't seem to be working as hard, or running as loud as it did, I don't see any change from before. I do feel better knowing that the unit is clean and oiled etc.

Am I mistaken in my belief that the fan should stay on until it reaches the set temp, or is the "short cycle" normal?

Thanks in advance.

Cheers,
Frank

[Robert]

Hi Frank,

Can you determine if there is any type shield on inside of furnace over the fan switch ?

IF there is a limit close by, does it have a shield over it ?




Thanks,
Robert

[Frank55]

Robert

Hi Frank,

Can you determine if there is any type shield on inside of furnace over the fan switch ?

IF there is a limit close by, does it have a shield over it ?

Thanks,
Robert

Huh? What language is that?

Kidding aside, we're in the middle of a storm . . . and the "access door" is outside, so I can't look at the moment; when the weather clears I can try to determine what the hell you're talking about, and in the worst case scenario, I can take a picture of the wiring etc.

Frank

[Robert]

Hi Frank,

Sometimes there is a small metal shield riveted inside furnace to block blower air from blowing over the fan switch which would cool it prematurely and cause it to open.


They can break and fall off, rust loose, or even have a close by limit switch where the fan switch should be and fan where limit should be.


When this is the case, what you have going on is normal.


You would then replace shield or switch parts, if you determine that was the problem.


Normal English really IF you should be DIY'ing your hvac.



Thanks,
Robert