They are NC, usually fail open. They are usually intermittent in the failure.
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They are NC, usually fail open. They are usually intermittent in the failure.
So, if the issue is the hi-limit and I turn off the main switch and jump the wires bypassing the hi-limit the furnace should work?Quote:
Originally Posted by MarkCO
I am pretty sure we tried yesterday and still no love.
Then , with the furnace working, it reached the programmed temp, turned itself off and tried again to restart even though theoretically it should have not, but this time although the igniter was glowing, no flame...Weird...That's why I am shooting for the CPU...I have a headache now...
There should be a flashing light and a sheet on the cover that tells you what the light means.
There is a HL, and a flame roll-out, or sometimes referred to as a High-high limit. It is very rare those go out and you should not bypass it.
The simple way to check the high-limit is to put a ohm meter on it. If it shows open, it is bad. If it shows very low, closed, it is good.
You need to have someone come out and look at it.Quote:
Originally Posted by bellavite1
Limit switches don't just go "bad". They go bad by continually being tripped. Boards are not very common to go bad either... The most common problem with boards is the blower relay built into them not turning the blower on.
Limits or any safety should never be bypassed unless for diagnostic purposes only...
I had my board go bad on a unit that was less than 10 years old.
The fan would kick on when it called for heat. Every once in a while I could get the furnace to fire, but then stop after a day or two, sometimes hours. Finally crapped out for good. Everything was cleaned, no LED's lid up. replaced the board with an Ebay new board and worked perfect. Saved $90 an hour on an HVAC guy, and did it all myself. Took the old board off, and when I unplugged from 1 wire, I plugged into other - so I would lose where they went.
GL!
They do go bad.. Just not as often as people (or technicians) think. Its funny to hear from the factory that most of the "bad" boards they get back for warranty aren't bad at all.Quote:
Originally Posted by fly boy
The other day I thought I had a board go bad on a commercial water heater. Called tech support and he said "Yup.... sounds like a bad board to me. Board costs $458" . I hang up with him, and I'm about to tell the customer when I find that the fuse had fallen out of the board and it just needed to be put back in.
I had the front cover bowed out a little bit, probably from the last time it was serviced when I was buying the house. It didn't push in the front cover switch enough to tell the unit the front cover was on it.
Just thought I would throw that in there.
Well, in my case it was the board:Quote:
Originally Posted by bryjcom
Way too much erratic behaviour, so I got me a board (Do-It-Yourself Plumbing and Heating, $109) and swapped it out.
Came right back on, has been running like a champ ever since.
The annoying part is that this is the 3rd board I change in about 9 years...
Never saw a burn, just a "darker color" around some of the components...
I wonder wether this is just a crappy brand (Goodman) or there is somenthing else causing the boards to fail.
I changed it last time maybe 4 years ago, and the darker color was around different components.
I am going to save this last failed board and compare it with the next.[Bang]
I will trade you a furnace install for that night force... [coffee]
It was a dirty filter, Im pretty sure anyways.