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Over limit switch is bad, when I replaced it, it keeps

Customer Question
Over limit switch is...

Over limit switch is bad, when I replaced it, it keeps blowing the fuse

Contractor's Assistant: I'll do all I can to help. How long have you been dealing with this?

Today

Contractor's Assistant: Do you plan on doing the work yourself?

Yes, I already have a replacement over limit switch but it keeps blowing the fuse when I use it

Contractor's Assistant: Anything else we should know to help you best?

Curious why it's doing that

Submitted: 8 months ago.Category: HVAC
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Answered in 46 minutes by:
11/10/2017
HVAC Technician: Phil, Mechanical Engineer replied 8 months ago
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 9,693
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Verified

Hello, there is an electrical short somewhere in the 24 volt control system or the printed circuit board... to test which buy a handful of fuses, then unplug one connector at a time from the printed circuit board until the fuse ceases to blow.... the electrical short will be in that item that you unplugged.

If you unplug all of the peripheral sensors and gas valve from the printed circuit board and it still blows fuses, then the printed board itself is bad and needs to be replaced.

.

Take a close up, exceedingly well focused photo of the wiring diagram glued inside the furnace/air handler door, and I will mark it up with trouble shooting instructions. Use the 'add files' link next to your send button to get the photo(s) to me.

We can go from there with training, coaching and diagnosis.... without a time limit, In depth with as much detail as needed , after you rate this answer:

Select the 'finish and rate your expert link' near the top of your page and click on it.

.

OPENING STATEMENTS

Important note about RATING my work:

I am a retired mechanical engineer and HVAC/electrical/ refrigeration and boiler contractor ... with 56 years in this business. The last 20 of those years consulting for major firms nationally.. and with over 8,000 questions answered here since 2009, with a 98.5% satisfaction rating.

.

All I ask is please respect me and my input by selecting the***RATING LINK***at the top of your page, that is the only way I am credited through the site. Rating does not affect your charges nor ability to refund if not satisfied.

.

If you need to be coached through a full diagnosis/repair,and wiring etc. for up to two days, and wish to be trained to use test instruments...... that goes well beyond' Just a simple Answer' of course, and goes beyond what most other experts here offer.....rate my answer so far positively.. . and I will deliver that training and coaching to you All on the same dime so to speak.

That said, I cannot guarantee that you will not do something unsafe, or cause damages. You take that risk.

.

Lacking a positive rating I can spend days helping a person at my own expense and loose my shirt, shorts and socks on the deal.

.

Phone call offers:

If you wish to accept the companies $25 phone call offer, if indeed they send you one, this will go a *lot faster, but it IS 100% optional... or we can continue here in this dialog box at no additional charge.

.

Tell me a lot about your technical background and instruments on hand so that I can coach you most effectively. We can go from here as you keep asking follow up questions without any limits … those actions are necessary to keep you on my list.

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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 9,693
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Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial

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