Janitrol (Goodman) GMP075-3 Heater Cycle Issue


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Old 11-14-13, 09:59 AM
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Janitrol (Goodman) GMP075-3 Heater Cycle Issue

Hello, I am new to this forum. We purchased our home back in August and now it is time to start using the heater here in Oklahoma. We have 2 of the Janitrol (Goodman) GMP075-3 REV A heaters installed in our home. One of them is not working/cycling correctly. Please see the attached link to the video i made of the unit cycling. When the thermostat is still asking for heat (not satisfied) after about 5 mins of running the flames stop, the blower keeps running as well as the inducer motor, then a few seconds later the flames start again and it will run for about another 5 minutes and continue to do this until the thermostat is satisfied.

When the video starts, the unit had already been running for about 5 minutes. At the 5 minute mark and 9:35 mark of the video you can see exactly what the unit is doing. All this continues to happen after I have cleaned the flame sensor and changed the air filters and made sure all of the vents are open.

Janitrol - GMP075-3 Furnace Cycle Problems - YouTube

The other unit in the home that is the same model is working properly. Can you please help me figure out what is wrong? Is the high limit switch bad or is it something else? How would i clean the coils just to rule that part out? This unit is connected to a condenser out side, and on top of the air handler are the outlets to the vents, below the air handler is where the return air is sucked in.
 
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Old 11-14-13, 05:44 PM
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Welcome to the forums.

The safety sensors very rarely go bad.

It sounds like your heat exchanger is overheating. That is usually caused by dirty filter, closed registers, blocked returns. Anything that reduces air flow thru the unit.

Do you feel a good flow of air from the registers ?

Cleaning the coils isn't the hard part...... getting to them is.
 
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Old 11-18-13, 07:06 PM
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I feel a good amount of air coming from the registers in the ceiling. I have replaced the filters and all of the registers are open, but it is still doing this. I have read that these models are known for the heat exchanger cracking inside. Would it be expensive to have someone come clean the A coil or is it something I could do my self. Before we purchased the house, all of the registers were very dirty, an older lady owned the home and could not access the vents to clean them. So I am sure that the coils are dirty. Also we had a HVAC company come out and do a summer tune up, which all they did was replace the filters and clean the dirt off the vents and put a little freon in one of the outside condensers.
 
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Old 11-18-13, 07:21 PM
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If you can get to the coils they aren't hard to clean but like I mentioned previously they aren't always easy to get to. The coil is mounted inside the duct work over the furnace.You might be able to post a few pics of your furnace and we could offer opinions.

http://www.doityourself.com/forum/el...-pictures.html
 
 

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