condenser unit pressure switch reset


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Old 06-20-06, 08:33 PM
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condenser unit pressure switch reset

thanks to all those that give their knowledge and time. i have been reading through all the posts with regards to intermittent condenser fan behavior. i had all the symptons and went ahead and replaced the contactor and capacitor. i was hoping to avoid the fan replacement, but it is still stopping and a jiggle of the motor shaft has some play so i am pretty sure the bearings are shot and i'll get to replacing that soon. however, my current problem is that i can't get my condenser to start-up when called to cool. it starts right up when pushing in the contactor, but doesn't stay engaged. i've searched for pressure switch resets and i don't see any. my wiring diagram shows high and low pressure switches... is there another method that i need to use? i have a voltmeter and i am ready to test away. when i test either side of the contactor i get 120v, which seems about 1/2 of what it should be?? i also don't get any voltage testing across the control wiring. any help is greatly appreciated.

Raul
 
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Old 06-20-06, 08:44 PM
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what type of unit do you have, make, heat pump or ac. measure your voltage across the contactor and not to ground. meaning you will have two power wires coming into the contactor from the disconnect box on the side of the house. measure from one to the next and you should have 240v. if your condenser fan has been acting up then the unit is more than likely cut off on high pressure. check the control wiring from point to point, typically the pressure switches are all in series so you can pull both ends and check continuity. be sure first however that you have control voltage into the unit from the airhandler/furnace by pulling the wires where they connect to the condensing unit first. yellow to common should have 24 volts. also after checking for the 24 volts you may want to shut the thermostat off to make sure you dont blow the fuse in your meter checking continuity on a hot circuit
 
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Old 06-22-06, 08:20 PM
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thanks, i appreciate your help. i finally got a chance to get out there today.

i have a carrier model 38EH024 ac condenser. i measured across the contactor as told and now i get the 240v on one side. i get 0v on the other, but it's a 2 pole switch versus the 1 pole i replaced so the other side isnt really used.

i checked the control wiring and i have 1v across the yellow/brown. for resistance i get 4 on the 20k scale. obviously something is going on there, but since i had no issues before, i'm thinking i fried something? my furnace fan won't shut off now either. i had it switched off with the condenser until the testing today.

i scanned my wiring diagram here

pictures here:

http://www.solyfunk.com/images/P1010001.JPG

http://www.solyfunk.com/images/P1010002.JPG

http://www.solyfunk.com/images/P1010003.JPG

http://www.solyfunk.com/images/P1010004.JPG

http://www.solyfunk.com/images/P1010005.JPG
 
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Old 06-23-06, 03:05 AM
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I'm not sure where you got the yellow wire that you are calling the "control wires." I assume you mean the low voltage wires from the thermostat that eventually get to the contactor? You should have brown and blue wires for 24 volts on the coil of the contactor. In your pics you have the wires off of the coil of the contactor. Which wires were there? I suppose, and the diagram is not clear for me, that the yellow wire could be from the T2 on the time guard switch, If that is the case then you are right.

If it were me, assuming the actual wiring matched the wiring diagram, check for 24 volts on the blue (or yellow) and brown at the coil of the contactor. If non there then check between the same brown wire and the yellow wire under the fan at the time guard switch. The time guard switch is not in any of your pictures but I can see the small yellow wires under the fan. If none there then move back to the yellow wire on the other side of the low pressure switch, leaving the second lead on the same brown wire. If non there, move back to the blue wire before the high pressure switch. If still none then it goes back to your thermostat. Wherever you get 24 volts you found the problem.

You could also reverse this and start at the blue and brown coming from the thermostat. You should have 24 volts. Leave one lead on the brown wire throughout and move the other from component to component until you lose power. There you found your bak component. However, the time guard likely has a delay on so don't expect it to give you voltage after that. If nothing else is found replace the time guard.
 
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Old 06-23-06, 04:05 AM
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Your head pressure switch is the red item inside the unit down near the compressor. It should have a small button on the end of it to re-set.
 
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Old 06-23-06, 10:30 AM
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thank you for your response...

Originally Posted by mdtaylor
I'm not sure where you got the yellow wire that you are calling the "control wires." I assume you mean the low voltage wires from the thermostat that eventually get to the contactor? You should have brown and blue wires for 24 volts on the coil of the contactor. In your pics you have the wires off of the coil of the contactor. Which wires were there? I suppose, and the diagram is not clear for me, that the yellow wire could be from the T2 on the time guard switch, If that is the case then you are right.
right. on my contactor there was the brown and yellow wires (left off in the picture since i was testing). the yellow wire is connected to the blue wire through the pressure switches as indicated on the wiring diagram. this all seems correct to me, though i do not know where the time guard switch is located. the layout drawing shows it in the panel, but it is not there. i'm assuming it is the round item with two black wires in picture P1010004.JPG. i will verify.

If it were me, assuming the actual wiring matched the wiring diagram, check for 24 volts on the blue (or yellow) and brown at the coil of the contactor. If non there then check between the same brown wire and the yellow wire under the fan at the time guard switch. The time guard switch is not in any of your pictures but I can see the small yellow wires under the fan. If none there then move back to the yellow wire on the other side of the low pressure switch, leaving the second lead on the same brown wire. If non there, move back to the blue wire before the high pressure switch. If still none then it goes back to your thermostat. Wherever you get 24 volts you found the problem.

You could also reverse this and start at the blue and brown coming from the thermostat. You should have 24 volts. Leave one lead on the brown wire throughout and move the other from component to component until you lose power. There you found your bak component. However, the time guard likely has a delay on so don't expect it to give you voltage after that. If nothing else is found replace the time guard.
yes, i get 0v between the brown and yellow wires on the contactor coil. i will try your methodology to troubleshoot the components. the only wires that go to the fan are the yellow/brown/black thicker wires. the smaller yellow wires go to the low pressure switch (green item in the picture). can you explain what you mean by no voltage after the delay? meaning i will have to a certain amount of time to test before i need to switch tstat off and then call cooling again? approx. how much time?

thanks again.
 

Last edited by raru; 06-23-06 at 11:03 AM.
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Old 06-23-06, 10:42 AM
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Originally Posted by mattison
Your head pressure switch is the red item inside the unit down near the compressor. It should have a small button on the end of it to re-set.
thanks, i pulled the motor for replacement so i'll be able to check it more closely.

btw, does anybody have a good source for replacement fan motors. i have a westinghouse 1/10 HP, 800 RPM motor and only see replacement units that are 825 RPM. the rated amps aren't any higher, so i guess it should be ok.
 
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Old 06-23-06, 12:13 PM
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I mean that the Time Guard switch is likely a time delay device that only trips on after a certain amount of time has past after the application of voltage. Some are settable and some are fixed. I don't have a clue what you have.

The round thing is a start capacitor. The Time Guard has three wires on it. Two yellow and one black. The yellow wire that connects to your capacitor should come directly from your Time Guard, and is probably located inside the unit where the low and high pressure switches are.
 
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Old 06-28-06, 07:29 PM
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ok, i haven't gone through the troubleshooting above since i was waiting on my new fan motor. i've got it in and pulled the wires but it's a bit different than the original. the wiring diagram is above and has the black to line, brown to the capacitor and yellow to the capacitor (condenser part) and to line... the new wiring says black and yellow to line and i have a brown and brown/white to capacitor. i was going to remove the yellow connection on the capacitor and wire directly to contactor and then connect both brown and brown/white to fan part of capacitor. does this seem right? would rather check then fry something and have to wait for another motor.

btw, i did find the time guard at the lower portion of the condenser, but no resets on the pressure switches.
 
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Old 07-02-06, 10:25 AM
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ok, the motor is in and the unit cools when the contactor is held in. i have no voltage on the control wires as they come into the condenser so i checked the tstat and also have no voltage at the R and G terminals. i went back to the control board in the furnace and found the 3A fuse blown. replaced that and when i tried to call for cooling it blew again. i replaced and checked the voltage and i get 29V across. is this within acceptable range or has the transformer/board gone out?
 

Last edited by raru; 07-02-06 at 10:56 AM.
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Old 07-02-06, 01:12 PM
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check for a short in the t-stat wires to the condensor.
 
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Old 07-02-06, 09:23 PM
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thanks covtiger...

perhaps i'm not understanding... but it seems that my furnace control board powers the tstat which sends feedback to the control board and then to the condenser control wiring. there is 29v on the board itself. one thing that is funny is that when i test across R and Y on the tstat i also get 29v, but when i switch to cooling it goes to 0v. is this correct, or is there a short in the tstat that is causing the fuse blowing?
 
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Old 07-02-06, 10:54 PM
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Originally Posted by raru
thanks covtiger...

perhaps i'm not understanding... but it seems that my furnace control board powers the tstat which sends feedback to the control board and then to the condenser control wiring. there is 29v on the board itself. one thing that is funny is that when i test across R and Y on the tstat i also get 29v, but when i switch to cooling it goes to 0v. is this correct, or is there a short in the tstat that is causing the fuse blowing?
That sounds ok. Disconnect the t-stat wires at the condensing unit and at the air handler and check them for a short. Many times that is what causes the fuse to blow or burn up the transformer. I had one last week that was shorted in the wires from the air handler to t-stat but I usually see it in the wires going to the condensor.
 
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Old 07-03-06, 10:52 AM
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ha, after thinking about it, it does make sense... once the circuit is closed then the potential is the same and thus 0v.

i tested all the wires between the tstat and the condenser for continuity and didn't have any problems. all were bellow 1 ohm on 200 scale, including the extension wire. one thing i found is that the wiring behind the tstat has crimp connectors and not much room once mounted to the wall. i'm figuring to go get a soldering iron and some heat shrink to at least do it right... not that would solve the problem since i tried jiggling the wires when the tstat was off the wall to see if that solved any touching wires.
 

Last edited by raru; 07-03-06 at 11:02 AM.
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Old 07-03-06, 11:40 AM
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When the fuse is blown does the indoor fan run? It shouldn't unless you have a transformer outside - 5 wire system.

I would replace the fuse and leave the t-stat wires at condensor disconnected. Turn on the fan, heater and cooling at the stat. If fuse doesn't blow you have isolated it to the controls in the condening unit (contactor, time-delay etc.)
 
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Old 07-03-06, 04:33 PM
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Originally Posted by CovTiger
When the fuse is blown does the indoor fan run? It shouldn't unless you have a transformer outside - 5 wire system.
it does, i don't have a five wire system, just the white and red wires. if the fan is in ON then the the relay clicks and it sounds as if the fan goes into high speed. if it is in AUTO then the relay clicks and it starts as normal. when the fuse blows, it relay clicks but the fan only continues in the low speed. i will pull the wiring diagram off the panel and post.

I would replace the fuse and leave the t-stat wires at condensor disconnected. Turn on the fan, heater and cooling at the stat. If fuse doesn't blow you have isolated it to the controls in the condening unit (contactor, time-delay etc.)
i did all those scenarios and no blown fuse, it only blows when the condenser wires are connected and call for cool. the contactor is new. the time guard is not actually installed, just the high and low pressure switches, but i see no resets. i test continuity through them and they seem to be closed. is there any way to test the contactor itself or perhaps somehow i wired it wrong since it is a 2 pole unit replacing a 1 pole?
 
 

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