Overheating?

sjclark11

Hi All. Ive had a Goodman GMP-075-3 for about 7 years now. Havent had any major problems since I installed it, other than a preasure switch and ignitor. This year I replaced the motor. It ran fine for about 3 months. Then I noticed it cycling quite often, so I traced it to the 7" temperature limit switch by the heat exchanger. I replaced the switch with no success. I then bypassed the switch while I measured the temperature at the switch location and got about 195 degrees. The swtich is rated at 170 degrees. What would cause this temperature to be this high, and what could cause this to happen all of a sudden? When I bypass the switch it cycles just fine.
I did check the schematic just to be sure I wired the motor to the board corrrectly and its fine. I also thought it was an ariflow problem so I removed a cover to allow more return air in..it worked a little better but not much...

Any ideas?

Thanks, sj

cleveman

The gasket on the inducer motor.

rbsremodeling

Is there coolant in the engine?

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sjclark11

yes there is coolant in the engine????

Anyway, i checked the gasket and I dont feel hot coming out around the mating point of the chimney.

greghvacguy

If you have ac the coil may be plugged.

sjclark11

Ill give that a try. It all started several weeks after i installed a new blower motor. maybe I knocked enough dust into the coils to restrict flow....thanks

Verbal

have you checked to see if you put the speed taps back on right? Some universals or even newer OEM replacement motors dont use the same color taps. Black is usualy cool, but heat could be any color. check the diagram on the side of the new motor to see the color code. to lower the temp in the heat exchanger raise the fan speed. Chech the difference between return and supply temps and compare it to the specs on the data plate. Or what they said above could be why, is the A-coil blocked?

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westernhvac

popped rings on the heat exchanger.

greghvacguy

Is the motor going the right way.

coolmen

recheck blower motor and squrrel cage. check rotation, speed tap, check static preasure on over all furnace to verify you are getting the correct CFM.
check that temp rise is per equipment specs (supply plenum/return plenum).check that no dampers or registers have been closed. residental apt building may have fire damper that shut on you.does the furnace when operateing sound much louder then normal.is insulation on the interier of the duct? did this come lose and block air flow.

Texahoma

Check the following, dirty filters, dirty evaporator coil, blower motor, gas pressure, static pressure, air flow calculation, duct work supply and return air.

sjclark11

Wow, you guys are great. I cleaned the AC coil and pretty much everything in there. That seemed to be the problem. I usually clean the coil each spring, but since my daughter has allergies I run my fan all the time to filter the air more thoroughly. I guess this caused it to build up faster. I do change the filters every 2 weeks consistently.

After the coil was cleaned the supply temperature at the 7" switch dropped backed down to normal 155. So far so good. I will continue to monitor and post back if the problem recurrs.
Thanks alot guys...sj

By the way, I replaced the blower motor a while back because the bearings started to squeal(I assume becasue they were dry) is there a way to rebuild these yourself? I still have the one I took out as a spare but want to know if I could fix it? Before I took it out i put a zurich fitting on the bearing cap and pumped it full of grease but the grease never travelled all the way through to the opposite side bearing....still squealed
Again, many thanks...sj

mmprattks1

Do you have an evaporator coil on the supply side of the furnace? If so did you check to see if it is restricted somewhat?
Also is the fan motor that you replaced rotating in the proper direction?