Coleman Presidential II 7670b 856

[Darren]

My Coleman Presidential II 7670b 856 furnace is acting weird...

The burner will come on fine and after it heats up the fan/blower will kick on and run for however long it should (I am assuming). But, then the fan will turn off and the burner will still be on and the fan will then proceed to turn off and on over and over again, in very short bursts. I have not let it stay like that for long as I will turn the furnace off (at the switch on the furnace itself as simply turning it off at the t-stat is of no use).

I'm not an expert, but it seems like the blower is coming on while it's still hot enough... but once it cools down, I can turn the power back on at the switch on the furnace and the blower won't come on. This only seems to happen after the furnace has been running and it's still hot. But, what is odd is that the fan/blower will start doing that even while the burner is still on/engaged, after it has been blowing the hot air for awhile (like a normal cycle).

Any advice would be greatly appreciated.

Darren

[Robert]

Hi,

Sounds like a faulty Fan & Limit Switch opening and closing. They can weaken over time and do this and can also not close at times and not open also.


Yours is Fan & Limit # 7975-3281 @ $13.21 + $6.75 shipping .

It can be seen and ordered from this page:

http://www.mobilehomerepair.com/ColemanGas.html


Scroll down left side to locate and click on pic for enlarged view.


Can't gaurantee this is problem, but it is a common one for your stated furnace operation.


If interested, please add to cart and order through PayPal or

call toll free to 1-877-263-7860 and charge to Visa or Mastercard.

Thanks.


Take care and best wishes,
Robert

[Darren]

I got the fan/limit switch and the old one was definitely the culprit, as I was not receiving voltage on the meter and now the new one is...

I have a problem however...

My furnace has two distinct switches; a limit switch and a fan switch - the fan switch on top and the limit on the bottom...

I'm not sure if this is why it's not turning on now or not, but I think it might be. Do I have to wire all 4 leads to the one new switch or is this new problem something else?

EDIT: I just checked my t-stat and it's now not getting any voltage... is that an indicator of something, when you take into context I just switched switches?

[Darren]

Okay, so I pulled the leads off of the new limit switch and taped them together bypassing the switch all together and I now get proper voltage to my t-stat and it turns on fine.... So, what am I doing wrong with that switch?

[Darren]

UPDATE: Even after returning the limit switch back to the way it was and replacing the fan switch with the new fan/limit switch, it still behaves the same way described in the original post.

[Robert]

Hi,


It is time to call a Tech. The Fan/Limit Switch is common for what you described, but as stated earlier, can't gaurantee it as I'm not there.


It is very common and cheap enough to try in this case. However, with it still doing same thing, I would not suggest spending any more on parts that may not be needed.


With it being a gas furnace, guessing at further possibilities could prove very expensive and dangerous.


It needs to be properly tested and inspected by someone with the tools/equipment to thoroughly diagnose it in person.


Sorry it didn't take care of it. You did good with it, but too dangerous to continue with DIY.


Take care and best wishes,
Robert