coleman gas furance blowing 3amp fuse

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coleman gas furance blowing 3amp fuse

Postby Guest » Sun Oct 12, 2008 9:07 pm

colemanm#g8c10020mud11a. The 3amp fuse on control board blows on call for heat.I unhooked t-stat wires at furance and jumped r-w same prob.Wiring is ok unhooked and read all low voltage wires.Would bad board cause fuse to blow.Thanks in advance for any help.Electricman
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RE: coleman gas furance blowing 3amp fuse

Postby Robert » Tue Oct 14, 2008 12:02 am

Hi,

Get a new wire and connect between t-stat W and board W and see what happens.



Thanks,
Robert
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RE: coleman gas furance blowing 3amp fuse

Postby Guest » Tue Oct 14, 2008 7:46 pm

robert, I tried the new wire nothing happened untill i hooked to r
and w then blew the fuse. Thanks for your reply any other ideals,I have tried everything i can think of. I unhooked all low voltage wires and tested them they showed ok ,do u think it could be the board. Thanks again, Electricman
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RE: coleman gas furance blowing 3amp fuse

Postby Robert » Wed Oct 15, 2008 10:13 pm

Hi,

With what has been checked, the board having a short is likely.

Have you removed it and looked at back for any burn spots ?


When you unhooked wires from furnace and jumpered R and W, was that at the board or at a terminal board for furnace ?



Thanks,
Robert
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RE: coleman gas furance blowing 3amp fuse

Postby Guest » Thu Oct 16, 2008 6:13 pm

Robert . i jumpered the r_w at the furance and the fuse blows , if i turn power on with t-stat unhooked ,sometimes both fans run but not all the time.after checking i found out they had changed boards but the furance run after that Then i was told the furance was running but through the nite the heat quit and he shut power off and back on then the fuse blew.sorry but i just found out this information,i havent charged a dime for my time so i may tell them to get a more exp tech although i think it has to be board or a control going to ground,I dont expect you to keep helping me but i do thank you very much for all you have done,THANKS AGAIN Electricman
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RE: coleman gas furance blowing 3amp fuse

Postby Robert » Fri Oct 17, 2008 3:54 am

Hey,

You're very welcome, happy to help. Can you send me a copy of the wiring diagram ?

With W wire at board disconnected and unit powered up with call for heat, IF all is fine.

Then when you connect the W wire to board and power back up and fuse blows, most likely a shorted circuit in the board.

Check and be sure that there is not high voltage coming in. Test across the W wire and C on board for 24vac.



Thanks,
Robert
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RE: coleman gas furance blowing 3amp fuse

Postby Guest » Fri Oct 17, 2008 8:37 pm

Robert. Ithink i found the problem or it healed itself. the last roll out switch was bad going to ground i jumped it out and furance run installed new switch seems to be ok. THANKS FOR ALLYOUR HELP AND Iwill try not to bug you guys so much Thanks again electricman
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RE: coleman gas furance blowing 3amp fuse

Postby Robert » Fri Oct 17, 2008 11:40 pm

Hi,

That's great, hope it keeps running good . You're very welcome, happy to help.


In a case like that, that is why I asked for wiring diagram.


Get you an inline ATC Automotive fuse holder and a lot of 3 amp fuses.


When this happens, splice it in at transformer power wire on 24vac side.

Then, looking at wiring diagram, reconnect one section of circuit at a time.

Keep following the diagram and adding a section at a time until fuse blows.


Then, if that wire is ok, the component it connected to is bad.



Take care and best wishes,
Robert
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