Big maxx fuse pops
- Thread starter Earlland
- Start date
acmikee
Well-known member
disconnect the "R" wire from the unit. jumper R to W if unit cycles on without blowing the fuse then its the stat wire or stat. if it blows then it the relay or a safety start elimating from that point
nehog
Well-known member
Model number?
I had that same problem.
A faulty high limit switch can cause this. It is located beside the control board. Disconnect the leads , jumper them together and power the unit back up. If the fuse does not blow, replace the switch.
Redraptor
Well-known member
I replaced one already.OK so I have the 20,000 btu Big Maxx which like others is working perfectly except it keeps blowing the 3 amp fuse on the board. First off it is not the thermostat nor could it ever be as the thermostat is simply a switch that by design shorts the R and W terminals which in turn activates the unit - ignore all mentions of thermostat and you will stop wasting time.
so what I found was if I leave the side cover off the unit works perfectly. Once I put the cover back on 10 min later the fuse pops. Here is my theory, heat from the exhaust pipe and blower is overheating the circuit board which is causing the fuse to then pop. I installed a 3" class A chimney with a somewhat restrictive cap and a 4" to 3" reducer at the furnace. I believe this is restricting the exhaust flow and causing blowback at the 4" connection. I will try opening up the cap at the top of the chimney and see if that works otherwise I may just leave the cover off as that does work fine as is. Food for thought
OK so the problem is fixed - Ignore all and any advice regarding thermostat as the thermostat simply works as a switch to complete the low voltage circuit. A jumper wire does the same so it can't possibly be the stat. I found the problem and the correct repair. Here is what I did to find this hidden gem. First my unit would work OK as long as I left the cover off. If I installed the cover the unit would die after about a minute and the fuse would be burnt. I replaced the circuit board and transformer to no avail. Next I pulled the item which may be the fan switch or high limit (see attached) due to the long thin arms on the switch it was sagging down and contacting the burner tube which then created a dead short burning the fuse. I bent the arm up just slightly put it back together and it's been flawless ever since.
Attachments
You are spot on.
I had the same problem, changed board / changed transformer / unhooked stat. Pop goes the fuse.
I read your post and another talking about alumium foil and did not see any ( till I pulled that switch out) bang, small 1 inch x 1/2 inch piece of foil laying right acrossed the switch. SHORT !!!!
5 mins later FIXED Thx you all so much, From Wyoming........
I had the same problem, changed board / changed transformer / unhooked stat. Pop goes the fuse.
I read your post and another talking about alumium foil and did not see any ( till I pulled that switch out) bang, small 1 inch x 1/2 inch piece of foil laying right acrossed the switch. SHORT !!!!
5 mins later FIXED Thx you all so much, From Wyoming........