# Goodman GMT-070-4 Furnace blows 3A Fuse



## bigMikeB (May 31, 2007)

If your blowing a fuse, you have a low voltage short circuit, which can be a real pain to find if you aren't experienced with this. Call a pro and cut the repair short.


----------



## undone (Nov 12, 2007)

If it runs for a time as you discribe, I doubt you have a short. I had a similar problem a couple summers ago. A 3 amp fuse kept blowing when a home owner would set the 'stat for cool. I was dumbfounded at first, but after I ran thru the routine of "process of elimination", it was determined the remote wire to the condenser was too long. After installing a 5 amp fuse, this problem never occurred again.
Try this. Don't worry, the transformer can handle it.


----------



## Bruce Mundy (Jan 1, 2008)

*Eureka! I found it!!*

In searching other forums (if I may mention that) I came across the following:

Q: "I have a 3 ton Goodman gas heat/elec air unit. When I turn on the heat in house after about 20-30 minutes it blows a 5 amp fuse. Had a service tech to the house it blew a 5 amp and a 3 amp fuse withing 45 minutes. He said what we have is known as a "ghost" he then pitched us for a new system, though he said our system is fine. It is now set at 66 degrees, with a 3 amp fuse in it, and it has not blown...yet...what can be causing system to trip the fuses."

A: "Look for where the limit switch enters the furnace. Remove the screws and remove the limit. Pay attention to how it sits in the furnace and bend it slightly away from the heat exchanger. I have found a few over the years that when they would heat up, the fan would push them and they would touch the heat exchanger and short out. It seam to only happen when their quite hot. I guess the metal weakens or something when hot"

This answer is courtesy of XENOS, webmaster on HVACMechanic.com.

Well, I pulled the limit switch on my furnace and found a very nice (if you can call it that) arc site on the top of the switch. See inside of left lead in photo. Apparently my limit switch was doing exactly as Xenos described.

Looking in the mounting hole I could see that the heat exchanger was directly above the switch by about 1 or 2 inches while there was probably 4 to 5 inches clearance below it. As Xenos suggested I bent the 7" leads so that the limit switch is about one inch lower than before. After reinstalling and buttoning up the furnace nows runs as long as it takes to heat the house!


----------



## bigMikeB (May 31, 2007)

undone said:


> If it runs for a time as you discribe, I doubt you have a short. I had a similar problem a couple summers ago. A 3 amp fuse kept blowing when a home owner would set the 'stat for cool. I was dumbfounded at first, but after I ran thru the routine of "process of elimination", it was determined the remote wire to the condenser was too long. After installing a 5 amp fuse, this problem never occurred again.
> Try this. Don't worry, the transformer can handle it.


How long was the wire to the condenser? I have seen many over 100' that don't draw an amp. Are you sure the coil on the contactor wasn't the issue? You did read the answer below that it was a SHORT in the limit switch?


----------

