[darque]

Heater is gas forced air and works fine in higher temperature daytime if in 60's, 70's. But if colder it won't turn on unless thermostat is manually moved back down then up so mercury trips again. Even had a hvac friend come out, test all of it, he replaced something but still same problem even after he checked it again but always during the day when it works fine. I put a new thermostat (non mercury switch) before he came and it didn't solve it either. It will go as hot as you want during the day and you can just put therm at 80 and it will go there. But when cold outside the only way to get it on for a few minutes each time is to rock the mercury and slowly creep up the setting, which I can't do from bed asleep. Any help appreciated:confused:

[wmproop]

I`m confused,, you do or don`t have a non-mercury thermostat,on it right now?

[labman]

There is a simple furnace/thermostat test at https://www.askmehelpdesk.com/heatin...ons-58313.html

[darque]

i`m confused,,,you do or don`t have a non-mercury thermostat,on it right now?

I have the original mercury Honeywell thermostat T8195B on it. I put on a non mercury one and heater still acted same way so I put original mercury therm back on.

The mercury contact works and completes circuit and turns on heater but when it's below a certain temp it won't keep cycling.

I just noticed now on a colder day that only the merc swtch for the blue lever is making the rheem criterion come on or off whether the therm is set to heat or cool. The other merc switch connected to red lever doesn't turn the rheem on or off when therm is set to heat or cool. Where can I find a manual for this thing? Thanks

[hvac1000]

Manual and install

http://customer.honeywell.com/techli...0s/69-0563.pdf

http://customer.honeywell.com/techli...0s/69-0564.pdf

[darque]

there is a simple furnace/thermostat test at https://www.askmehelpdesk.com/heatin...ons-58313.html

Therm for heat works fine if the outside temp is 65 or above but if it's 50 outside it just burns for a minute or less and blows for maybe 3 or 4 short cycles a minute or so a piece and then stops without the mercury moving at all. If I then just rock the mercury once it will start again and go through the same 3 or 4 short cycles for about five minutes total and stop again with the mercury still sitting in same spot... thoughts?:confused:

[hvac1000]

Jump the thermostat for the heat cycle. White (W) and Red (R) should do it. It might be easy to do this back at the furnace unless you want to take the stat apart. When it cold and it will not run jump it out and let it run. If it runs it is the tstat if it stops running like it has before it is a furnace problem.

Simple test

[darque]

Jump the thermostat for the heat cycle. White (W) and Red (R) should do it. It might be easy to do this back at the furnace unless you want to take the stat apart. When it cold and it will not run jump it out and let it run. If it runs it is the tstat if it stops running like it has before it is a furnace problem.

Simple test

Thanks for the help, u mean to connect W and R correct?

[hvac1000]

Yes

[darque]

yes

Aha, jumped r & w and same thing, just heats for a few minute long cycles then stops. And then disconnect r/w and reconnect it starts again with same behavior. Thoughts appreciated on what next... :confused:

[hvac1000]

The trheremostat seems to be OK.
Make sure the air filter is clean or replace it.
Does the blower fan ever come on?
If not that could trip a oevrheat safety shutting the furnace off.
Whenever you cycle the thermostat you are you are doing a reset of the control and that is why it comes back on.

[darque]

The trheremostat seems to be OK.
Make sure the air filter is clean or replace it.
Does the blower fan ever come on?
If not that could trip a oevrheat safety shutting the furnace off.
Whenever you cycle the thermostat you are you are doing a reset of the control and that is why it comes back on.

Blower does come on. Filter is clean but is there a way to test it's not the filters like taking out altogether for a test or.. because it has a funny set up as you see in the pic. The heater is off the ground about a foot high and directly under it is the filter. But also there is a filter in the door of the closet as well. I've taken the door filter out. (as you see it laying on floor in picture) left door hang open, etc. to try see any change but no luck, ideas? (btw the AC has no issues if it matters) thanks, I really want to solve this:(

[hvac1000]

There is something wrong with the install of your furnace according to the pictures. Your return air is supposed to be totally isloated from the combustion air for the burner. There is a grill there in the door but I see no effective way to seal it off. Since the furnace is in a closet it is supposd to be feed combustion air from the outside. Now I will admit those pipes might be somewhere there but they do not show on the picture. See if you can take a few more pictures.

I am just wondering if this setup is causeing some or all of the problems.
Your main complaint really does not make sense to me because the furnace should run no matter what the outside temp is to start with.

BTW there is NO storage allowed in that closet also. Just thought I would mention that fact.

[wmproop]

Now! my friend you have determined that your problem is in the furnace not in the thermostat, have you checked and cleaned the flame senser,,

[kanrdc]

heater is gas forced air and works fine in higher temperature daytime if in 60's, 70's. but if colder it won't turn on unless thermostat is manually moved back down then up so mercury trips again. even had a hvac friend come out, test all of it, he replaced something but still same problem even after he checked it again but always during the day when it works fine. i put a new thermostat (non mercury switch) before he came and it didn't solve it either. it will go as hot as u want during the day and u can just put therm at 80 and it will go there. but when cold outside the only way to get it on for a few minutes each time is to rock the mercury and slowly creep up the setting, which i can't do from bed asleep. any help appreciated:confused:

Need more info to help you. Make, Model, 90% or conventional venting, standing pilot or electronic ignition? First guess is cooler air is condensating your electronic ignition down your flue pipe. Contact me with more info, I will be glad to help if I can.

[labman]

Note to kandrc: Site policy is not to ask or answer questions by PM or email.

You are asking some good questions. Many of the better people on this forum are AWOL. We could use another good man.

[hvac1000]

Check all the 120 volt wiring especially the ground circuit from the house oanel to the furnace switch. Then check to make sure the bare or green ground wire lands in the furnace. Also check all ground wires in the furnace for tightness.

Post your model and brand name so I can pull a diagram if I have one.

[wmproop]

thnx for the help, u mean to connect W and R correct?

\\\ok,, now you have determined,the thermostat is bypassed and you still have the prob. somust be in the furnace,, have you checked and cleaned the flame senser?

[darque]

Check all the 120 volt wiring especially the ground circuit from the house oanel to the furnace switch. Then check to make sure the bare or green ground wire lands in the furnace. Also check all ground wires in the furnace for tightness.

Post your model and brand name so I can pull a diagram if I have one.

Thanks for everyone's help, we'll get this...

Some more pictures. It seems as if it is some switch or sensor getting automatically tripped but it doesn't need anytime to dry or cool down or anything to restart it, just rock the mercury two seconds after it stops its four minute cycle and it goes again for the same four minutes. When it's running it all functions well so would that rule out a grounding issue?

And the reason it runs fine when indoor/outdoor temp is warmer is as I've observed the mercury is moving back and forth with rise and fall of temp. it just needs to run longer when it's colder outside/inside:confused:

[darque]

Rheem criterion gas furnace