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BillyHvac
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22090
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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my 3amp fuse keeps blowing every time i call for heating,my

Resolved Question:

my 3amp fuse keeps blowing every time i call for heating,my cooling and fan speeds works fine. i used a new piece of t-stat wire and also jump the r/w from the furnace and it still blows, changed the t-stat wires also, what else should i check. it only happens on heating
Submitted: 5 years ago.
Category: HVAC
Expert:  BillyHvac replied 5 years ago.

This can be any 24v wire in the furnace itself so look for any pinched or scraped wires...does the gas valve have a on/off switch?

 

 

Customer: replied 5 years ago.
yes it has a on/off switch
Expert:  BillyHvac replied 5 years ago.

run everything the same except turn the gas valve to off...tell me if short remains.

 

 

Customer: replied 5 years ago.
ill have to check once i get home
Expert:  BillyHvac replied 5 years ago.

just respond to this when ready.

 

Billy

 

Customer: replied 5 years ago.

ok, ill most likely be a little after 4:30, ill make sure thats the fist thing i do when i get home.

thanks

Expert:  BillyHvac replied 5 years ago.

 

I wish you luck

 

 

I will be online later tonight and will respond as soon as possible.

 

 

Customer: replied 5 years ago.
Ok bill,
I just got home. Checked the line voltage, from black to white 122v
Black to ground 122v.turned off the gas pilot switch then turned on the remote switch by the furnace.
I get the green led flashing for 2 sec. Then the fuse blows again!
Expert:  BillyHvac replied 5 years ago.

thank you...dont want to cost you a bunch of fuses...

 

Unplug all the wires from the safetys and tape the ends of them...pretty much all we will have is the board standing alone with wires going off to the safetys...but they will not be hooked up.

 

 

Customer: replied 5 years ago.
Ok , induction fan comes on with out burning the fuse. I found a bad door switch also witch I jumped.
Know what?
Customer: replied 5 years ago.
Ok , induction fan comes on with out burning the fuse. I found a bad door switch also witch I jumped.
Know what?I also get 5 flashes on the board
Expert:  BillyHvac replied 5 years ago.
Now..one at a time put safetys back into circuit...
Customer: replied 5 years ago.
I placed each safety back one at a time, when I put the last roll out switch the fuse blow. I have a extra
One to replace it with. What's next
Expert:  BillyHvac replied 5 years ago.

remove the 2 wires from the roll out..use a paper clip as a union..slide each spade connector onto the paper clip..tape so no metal exposed

 

(we are bypassing the switch)...

 

Most shorts were on the limit switch mounted on the front wall...the switch inside would touch the exchanger...

Customer: replied 5 years ago.
I changed the roll out switch but it still blowing the fuse
Expert:  BillyHvac replied 5 years ago.

Did you check the limit I described?

 

 

Customer: replied 5 years ago.
I jumped the rollout switch but it still blows fuse. What limitswitch was you refuring too

Expert:  BillyHvac replied 5 years ago.
the main overtemp limit on front wall
Customer: replied 5 years ago.
That was the first safety switch I put back on line from the lo circuit board
Expert:  BillyHvac replied 5 years ago.

Ok,

 

the whole idea as you see is process of elimination. Can you take a pic of the schematic and post it here?

 

 

Customer: replied 5 years ago.
Ok
Expert:  BillyHvac replied 5 years ago.

I will stand by..

 

 

Customer: replied 5 years ago.
Hey bill, I found that the hi-temp switch was
Ground to the wall
Expert:  BillyHvac replied 5 years ago.

 

Yep....that is the famous one I was talking about.

 

You good now?

 

 

Customer: replied 5 years ago.
God bless you for your help and patience
The unit fired up and fan flower is running

God bless you
Expert:  BillyHvac replied 5 years ago.

Thank you for your patience. Without help on your it is not possible.

 

Have a good night.

 

Billy

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