AC wont turn off Coleman Pres. II Model 7670C856

[deepeepee]

First off, thanks to you and the others who have posted similar problems in the past. Without them, I would not be able to troubleshoot this issue on my own.

We have a Coleman Presidential II (SN 018364164) Model # 7670C856 Gas Furnace w/ AC unit outside. When running the AC unit, the thermostat is not controlling the temperature. It is a 2 wire system. The heating "side" of the furnace works fine and is thermostatically controlled.

We must use the “heat/cool” switch to turn the AC on and off. All switches (Fan On/Auto and Heat/Off/Cool) on the thermostat (Honeywell MagicStat CT3200) are not functional when the switch on the front of the furnace is set to cool. The condensing unit turns on immediately regardless of thermostat setting and COOLS home without reguard to T-Stat.

I have not measured any voltages at this point. The furnace model number has a “C” in it and I can’t find the proper manual that dictates which replacement parts to use. Previous posts here indicate that that the problem could lie with the A/C reversing relay (PN 7670-3071), however, I am fairly confident that the “relay” that my furnace has is a Honeywell PN R822D-1014 instead of the one listed above. This relay appears to have been added because it is not mounted in the control box like the one to the left, which is screwed in from the back of the box. I am not sure if this is the proper relay. I have a general idea of how my current relay is wired to the current “heat/cool” switch and to the thermostat, but I am unsure of my next move…Any help would be greatly appreciated

PS My blower is clearly labeled PN 7670B692, which leads me to think I should be looking at "B" model parts??!!!

Thanks again

[Robert]

Hi,

When you place furnace switch on Cool at start of cooling season, the a/c is supposed to come UNLESS room temp is below the temp setting on t-stat.


T-Stat must be set to Auto and Heat.


Set temp lever where you wish it to be.


When the home cools below the temp setting, your t-stat which is set to Heat senses this and closes to turn heat on.


The signal goes to reversing relay which turns off a/c and sends signal for heat.


When signal gets to heat-off-cool switch, it being set to cool stops the signal from actually turning heat on because switch relay is open to heat and closed to cool.



Sooooo, nothing is on at that point.


Home starts to heat up.


When temp climbs above t-stat temp setting, the t-stat "thinks" it is satisfied for heat and opens.


This stops signal at reversing relay which opens heat signal path and closes cooling path, so a/c comes back on.


Welcome to 2 wire hvac 101.


When the above does not happen with t-stat on auto-heat and furnace switches at auto and cool, it is usually the t-stat or reversing relay.


You look for parts under the furnace model number and/or your a/c control box number..


Thanks,
Robert

[deepeepee]

Just got word from my wife that there is nothing wrong with the A/C, it is working as you instructed us...Operator error from the start....Much thanks, Robert

Dan Peternel

[Robert]

Hi Dan,

You're very welcome, happy to help. 2 wire set ups are confusing unless you have the info given.

Hoping to soon have an article on this, as I get tons of questions such as yours, even from hvac service techs.


Take care and best wishes,
Robert