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Heating & Air Conditioning

Fuse blowing, A/C not working

16 years ago

I changed my Thermostat to a programmable one yestersay and a 20-min project has become a 2-day affair. Its a 5-wire system, Which is installed the way I took the other out. But now everytime I turn on the AC, the 3-amp fuse blows out in the Furnace unit. Im in Texas and sweating alot, any help or suggestions would be greatly appreciated!!

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Comments (6)

bob_brown
16 years ago
Check the wires closly in the thermostat. It sounds like 2 wires are touching when they are not wanted. If you do not find a short, describe the wire connections on the thermostat, connections in the furnace. Tell us what kind of furnace you have. Heatpump, etc.
matt-july
Original Author
16 years ago
My AC unit is a Carrier-Central Air unit with no heat pump, and the Furnace is a Carrier-Heatwace 80 Induced-Combustion Gas Furnace. Both about 1-1/2 years old.

I switched the wires between the Rh and Rc connections on the thermostat, This made the AC work, but not shut off. It goes below the set temp and I have to turn it off manually.

Another note, turning the heat on now blows the 3-amp fuse.

I obviously have it wired up wrong on the thermostat, but I don't know the right way to do it now. Any more help is greatly appreciated.
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OK, let's concentrate on the ammeter. Does this ammeter mount in a metal panel? or is the dash plastic? If the dash is metal, it is possible that the ammeter is shorting to ground internally, but don't rush out and buy another ammeter yet, there are some tests to do first. Do you own a multimeter (that will test volts, ohms, and continuity)? If not, you need to buy one before doing any testing. This may take several posts to get to the root of the problem. If the ammeter mounts in a metal panel, set the multimeter to Ohms or to "continutity" if you have that feature on your meter. This test applies ONLY if the ammeter mounts in metal. If dash is plastic, skip this test. Unplug the wires from the ammeter. Place one of the test meter leads on one wire post of the ammeter and the other test meter lead on a clean, bare metal part of the tractor. You should read "infinity" if using an Ohmeter, or "no continuity" if using continuity setting. Test both of the posts on the ammeter and they should both show infinity or no continuity. If either post of the ammeter shows continuity to ground, the ammeter is shorted internally and needs replacing. Get back with some test results. Alternatively, you can test for a shorted ammeter by connecting together the 2 wires that attach to the ammeter. If you connect the 2 ammeter wires together and the fuse does not blow, you have proved the ammeter to be shorted.
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Craftsman Kohler V-Twinn 22 HP 50" Deck I had the same problem...fuses blew as soon as I would turn the key. I done the wire check, battery, everything. I jumped across silinoid to start but the tractor wouldnt move or blades wouldnt turn on. When tractor was running when releasing clutch I would start to move but the mower would start to die until I pushed the clutch back in. I finally found a plug on the left side of the engine. (I think it is called an ammeter.) I unplugged this turned the key and to my suprise the fuse didnt blow. So I jumped on and it started. I put the mower deck on and again to my suprise the blades came on. Now the mower was running rough and maybe backfired a few times but the damn grass is cut. Will buy this part tomorrow lol. hope this helps someone.
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bob_brown
16 years ago
Use a jumper to connect Rc + Rh, then connect the wire to either screw connection. Test the fan on function with the cool/heat in the off position. If the fan works(after the time delay) then the fan function works. You have a short in the heat control circuit. What are the wires going to? Is one a common ground?
matt-july
Original Author
16 years ago
Ok i put the jumper between the Rc and Rh, Both the heat and AC now turn on and off when I switch between them on the Thermostat, But neither turn off at desired setting temp on the Thermostat. I have tried 2 different thermostats, one programmable and one non, just to check if they're working.

I cannot get the Fan to work by itsself with the temp setting on off.

I now have a "Blue" wire unattached, it runs to the ventilation control (Ch and jumpered with Cc)

All the Wires run from the furnace, to a Ventilation control, to the Thermostat.
bob_brown
16 years ago
Well, it seems that the blue wire is not what you expected if the fuse no longer blows. Normally the temperature has to reach the next degree increment to turn off. I have seen several brands that work like this. I have never seen a Ch and Cc. It seems to be an additional setting for the stat. Are you sure it needs to be jumpered? This could affect the stat if done wrong. I have seen blue used as a chassis ground, which would explain the fuse blowing. Check the battery for voltage, if low it will affect the thermostat. Some stats are very temperamental with low voltage. If the color wires are nominal, green should run the fan. One wire jumpered to the red wire should run the fan, after the delay ends. If you jumper grounf you will blow the fuse. Check at the furnace end for where the wires connect. If the green is connected to G, then this would be correct.

What kind of ventillation control?
matt-july
Original Author
16 years ago
First of all thanks a ton for the help!

I tested the fan at the furnace and it kicked on, which confused me a bit. Well, I finally saw that there was a switch on the Vent. control and it was set to override, Which made the fan not work apparently and caused the AC and Heat to run no matter what. I flipped that to on, The fan works, the AC works and turns off so does the heat!!!

Thanks so much for your time and help Bob, its is greatly appreciated!

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