The control circuit fuse blows on a htg or cooling call so removed all but 24vac to t-stat. I then called for heat/ cooling and fuse wouldnt blow. hooked them back up call for just fan still wouldnt blow..... led's are also lit must be some kinda fault? seems to only blow when calling for htg or clg
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Re: control fuse keeps blowing on a htg/cooling call
There is a short somwhere in the low voltage circuit. Test the continuity of the remaindimg wires to ground, you should have no resistance, if you do have resistane the wire will have to be replaced. Also, the thermostat can have an internal short which can cause the fuse to blow.
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Most problems with air conditioners (A/C) are electrical problems, not Freon problems. This is an article containing tips on troubleshooting A/C electrical problems.There are two circuits involved in an air conditioner. There is the line voltage, 120 or 240 Volts Alternating Current (VAC) and the control voltage (24VAC) circuits. The control voltage is used to turn on the line voltage compressor and motors.
In troubleshooting A/C problems you have to determine if the problem is a control circuitry issue or a line voltage issue or component.The first thing you want to do is determine if you have line voltage. You check the breaker at your main fuse box and any fuses at the disconnect box next to the outdoor unit. To check the fuses, turn the power off at the breaker box and remove the fuses. Take a multimeter and place it on the resistance setting. (Rx1) Place one lead on one end of the fuse and the other lead on the opposite end. If the meter arrow goes to zero, the fuse is good. If it stays at infinity (a sign that looks like an 8) it is bad or open. Replace the fuse, as they will blow especially during initial season start-up of the compressor.
If you take your thermostat cover off you will see several small wires. If you take a jumper wire and touch the red wire to the green wire the indoor fan motor should start. This tells you that you have 24VAC control voltage. If it doesn't start, there is a transformer or control voltage wiring problem.To further confirm you have a control voltage problem, remove the access panel to the outdoor unit. You will see a contactor. Use an insulated screwdriver and manually push that contactor in. (Make sure your hand is on the insulated portion of the screwdriver) If the outdoor fan and compressor start, the problem is in the 24VAC control circuitry.
Check for input line voltage at the transformer with a multimeter set on 120 or 240VAC. If you have line voltage, check the output side of the transformer for 24VAC. Trace the problem from the location you have voltage to the place you do not, but should have, using the wire diagram or common sense.
If you are not getting any response from your furnace and your furnace is not working, then the first thing you want to check is that there is power coming in.
If you have 120VAC coming in, then check to see if you have 24VAC coming from the transformer. If you do not have the 24VAC from the low voltage transformer then the transformer has burnt out. Power surges and especially brown outs (low voltage) can cause the transformer to burn out.
If there is 24VAC coming from the transformer secondary then check to see if there is a fuse in the low voltage circuit. Sometimes the fuse on the circuit board and often are an automotive type fuse that plugs into the circuit board. Sometimes the fuse will be an inline fuse that will be in a black round tube type holder. If the fuse is blown do not replace with a higher amperage fuse, you will cause more damage, or blow the transformer.
If the fuse is blown then unhook the t-stat wires and check again. This will tell you if the short that blows the fuse is external to the furnace or internal.
Now if all of that checks out then the next thing would be to check the low voltage safety circuit. Things such as door switches and high limit switches are all possibly included in this circuit, if any of them are open the heating system will not work.
As a last resort, the problem could be in the circuit board. They do go bad and can shut everything down also. Most circuit boards will also flash a LED light to give you a code for what is wrong and why the furnace is not working.
Count the number of flashes and then check the inside of the front cover to see what the code represents.
This will give you a basic progression of things that you can check through. Using an electrical meter is essential to being able to diagnose and troubleshoot the heating system. If you do not have one and/or do not know how to use an electric meter proficiently, then find someone to help you that does know how to use one well to help you.
Yes its a short. I've seen a weakening component cause that but 99% of the time its a short. Look where your control enter your o.d. unit. The wires can rub on the metal where the small hole is for the wires to go through. If your o.d. unit has any low voltage wires inside where the piping to the compressor are, look there. A low or high pressure switch may be installed and the low voltage wires inside can rub on a copper line causing an intermittent short. Look anywhere a low voltage wire can touch anything , other than intended points. If its a component then you may end up with new parts all over and still have a short. The control wires can get damaged by varmits in the attic, crawl space, and where the wires go through the wall or sophet. To isolate it may take a pile of fuses or a transformer with a micro-breaker can be installed. Basically has a 3-5amp micro breaker that trips and can be reset. If you were to remove all control wires leading to the o.d. unit, start the cooling, and it shorts then your short is not at o.d. unit. With o.d. control wires wired in at the ahu, disconnect the low voltage wires from the o.d unit. Cycle cool and if it shorts, the wire between is the cause. If it don't short, then you know its at the o.d. unit. At the o.d. unit, if it has any low voltage safeties(low pressure, high pressure, delay timer, ect...) you can maybe bypass all to allow the contactor to be the only component wired in the low voltage circuit at the o.d. unit. And if it shorts keep chasing it. Bugs and geckos can get behind circuit boards causing a short. Ants in any components can cause a short. Hard to help more from here. Above all, work safe!
Generally the 24VAC terminals are marked on the furnace board. If it is blowing fuses, check for a short circuit in the thermostat wiring. I have found that the short is usually at the condenser unit where the insulation deteriorated. Many times caused by a dog or cat chewing on the wire. To test, remove the thermostat connections at the control board and power up to see if fuse blows. If it doesn't, you found your problem. Good luck.
You have a short circuit, which is obviously dangerous. Your blower motor is controlled via a 24VAC control circuit, but is 120VAC. The circuit board and gas valve are probably history, but it needs to be troubleshot to determine the scope of the damage.If you remove T stat you will see several colored wires. The red and green wire when touched together should cause your fan blower to run. If that works when you bypass t stat the t stat is gone. The red to white will open your gas valve on your heater. The red to the yellow or blue will start your AC compressor or condenser fan motor. Be careful with the yellow and blue wires as one is actually a neutral and one goes to the AC contractor on your condenser unit contractor. Hope this helps!
check the stat wires for damage at unit the orange wire controls the reversing valve for heat cool on heat pump if wires look ok then un hook tue orange wire if doesnt blow fuse then the reversing valve coil is bad hope this helps
BEWARE OF HIGH VOLTAGE! 220VAC CAN KILL YOU! That said, it sounds like you have a short in the control (24VAC) curcuit to the condenser. A mouse probably made a home in the control compartment of your condenser. BEWARE OF HIGH VOLTAGE! 220VAC CAN KILL YOU!
You have a low voltage short. A lot of low voltage shorts come from the wires that go out to the outdoor unit. Go outside and inspect those wires and that they are in good condition. Also check for any splices in those wires that they haven't degraded in any way. This is the only thing that will blow the fuse. That's why it's only 3 amps and based on the size of your fuse, it's a gas fired unit right? Have a great day!