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R.G., HVAC Technician
Category: HVAC
Satisfied Customers: 319
Experience:  20 yrs. experience as HVAC technician, state certified contractor.
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Hi, have a question about York Diamond 80 HVAC system

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Hi, have a question about York Diamond 80 HVAC system

R G : Hi, I am R. G., sorry you're having trouble today, I will do my best to assist you in resolving you're issue.
R G : At this
R G : At this point you have original stat back in place?


R G : Okay and nothing will work?


R G : Can you access your furnace?

we have tried resetting the on-off switch to reset the circuit board on the HVAC unit


yes, we can access it

R G : Okay at the control board where thermostat wires connect there should be a small 3 or 5 amp automotive type fuse
R G : Can you locate it and check to see if it is blown?

ok we are lookin

R G : Okay I am looking for a manual Tory and before specific also
R G : To try

we found it. it is blue. looks like there are 2 wires inside at the middle that aren't connected

R G : Is the fuse blown?



is it possible to send you a picture

R G : Okay replacing fuse should get you back going
R G : Yes you can use paper clip icon to attach it here

Full Size Image

R G : Yes it's definitely blown just replace it with same rated fuse, looks like a 3 amp

is this something that can be bought at home depot, lowe's, or ace hardware?


yes it is a 3 amp fuse

R G : It is an ordinary automotive fuse can get at wal mart or any parts store or could rob one from your vehicle

the bigger question is why the fuse blew in the first place

R G : You must of had A wire shorted out somewhere when you had changed wiring causing fuse to blow
R G : Was unit working before with old stat?

although our honeywell thermostat didn't have a C wire, the HVAC circuit board did. We followed the instructions for venstar add-a-wire, using a diode connection between the Y and G. on the circuit board, the Y blue wire was intertwined the a red power wire from the A/C unit. Both wires were coupled with the diode wire, and a single wire from the diode was screwed onto the Y terminal of the circuit board. this was the only time we got power during this new thermostat installation attempt. when we tried to turn on Heat, the unit briefly ran, and then blew a fuse


yes, unit worked with old stat just fine, but our bedroom is on terminal vent, and it gets hot. so, we wanted a remote unit to control temp using ambient temp in bedroom. this is where all our problems have started, trying to follow so-called easy DIY installation.


here is the video we followed:

R G : Okay replace fuse and make sure unit works with old stat if not let me know and we will troubleshoot further if so you can get a batteryowered stat that doesn't require the C wire or you can remove green from G at stat And furnace and connect to C then connect G to Y at furnace. Air and heat will work but Continous fan will not if wired like this
R G : Not familiar with the venstar add a wire system but I can look it up if you want to use it

but, our wiring at the control board looked different. there was a single white wire from the AC line to the C terminal, and the red wire from that line was coupled with the blue wire at the Y terminal. there was a green G wire, a white W wire, and a red R wire.

R G : Yes that is correct wiring , you can unhook the green from G at stat and furnace and connect it to C at stat and to C at furnace with the white from a/c. Then take a small piece of wire and at furnace connect G to Y leaving the red and blue on Y also
R G : This will let heat and cool work but Continous fan will not

yes. we tried that, but it was after the fuse was already blown, only we didn't know fuse was blown


huge pain in the ass


and we live in the South!

R G : Yes it can be frustrating
R G : Im in alabama
R G : Get fuse replaced and let me know if you need anything further.

so, in your opinion, the fuse is the problem, and that new stat that requires C wire can be installed using the G to C method you described. we never use a continuous fan. it would obviated the need for extra wires.


ok thanks

R G : Yes nothing will run with that fuse blown and method above is the easiest if your ok with not having the Continous fan option

all we have is 10 amp fuses. can we use one of those for tonight?

R G : I wouldn't recommend that if you cross something up it will burn out transformer before it blows that fuse causing even bigger
R G : Problems


R G : Just by chance look inside furnace on side to see if there is a small envelope taped or glued to side some units have this with a spare fuse and literature on unit in it

no such luck


we will go to auto zone in the morning and get some new fuses

R G : Okay i will be here till the morning and back on to or row evening late. Just reply back if need any further assistance and I will answer as soon as I am available
R G : Thanks for your patience

Ok, will let you know what happens

R G : If you rate answer now you can still come back to it for further information at no extra charge or you can wait until completed to rate
R G : Okay thanks, XXXXX XXXXX
R.G. and 2 other HVAC Specialists are ready to help you
Customer: replied 4 years ago.

Replaced old fuse, wired thermostat and HVAC terminals to use G wire as common (instead of using the Venstar Add-A-Wire system), and voila, system works! Thanks for all your help.

Thank you. Let me know if need anything else. Good work

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