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When T-stat call for COOL, always have to wait for 3 minutes before it starts..

When T-stat call for COOL, always have to wait for 3 minutes before it starts..

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  #1  
Old 10-12-13, 01:44 PM
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When T-stat call for COOL, always have to wait for 3 minutes before it starts..

When T-stat call for cool, the contactor engages for about half second, then spring back off immediately, I checked 24V at that time, 24V is at the entrance of the condenser, but not at the contactor terminals, 24V is at one leg of the time delay, not the other leg, 3 minutes later, condenser(both compressor and fan) starts automatically. no matter when I start the system, it always wait for 3 minutes before the condenser really get started (After the contactor kicks in for half second at the begining). I changed time delay module and the contactor, still work the same. Looks to me the time delay mudule cuts it off for some reason, but why ? Any idea? Thanks.
 
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Old 10-12-13, 02:02 PM
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Now you have two threads running with the same question in it.

The time delay module will not allow the compressor to turn on for three minutes so that the compressor can't short cycle. Your timing module is allowing the contactor to activate for 1/2 second and then waiting the three minutes which is not normal.
 
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Old 10-12-13, 03:54 PM
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Here is a link for the service manual for your unit: http://johnstonesupply9.com/TechDocs...VICE%20MAN.PDF Check pages 181 and 182 for testing procedures for the delay amd contactor. The wiring schematic is on page 207. Verify all wiring is on the proper terminals according to the schematic.
 
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Old 10-12-13, 05:09 PM
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I have seen this a few times when mercury stats control a unit.
The spring coil pops into place causing the mercury to rock around in the glass tubing that houses it.
 
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Old 10-12-13, 06:06 PM
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PJmax, Would you please close the other thread (the one for capacitor) for me. and leave this one open, Thanks.
 
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Old 10-12-13, 06:36 PM
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It was a digital T-stat, I just put a new digital T-stat in, hope that was the problem, but no, still the same. So, after I shut the AC down, If I wait for 1 minute to start the AC, nothing happen (I did not wait for 3 more minutes, may be I should, and see what will happen, I'll do that Tomorrow) If I wait for 20 minutes to start the AC, it will activate the condenser for half second (contactor button pulled in for half second, fan turns about half turn, compressor kicked on for half second too, I can hear it) and then contactor button pops out, everything stop, and 3 minutes later, it kicks on automatically, everything run fine after that (until next cycle, then it will do the same thing again). I have already replaced capacitor, contactor, time delay, and T-stat. CAN THE CONTROL BOARD CAUSE THIS PROBLEM ??
 
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Old 10-12-13, 07:18 PM
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If you check the schematic on page 217 in the manual I linked earlier it shows you have a low pressure and high pressure switch. This could also be a cause for your problem. To test (for a short test only) you can bypass these switches one at a time and see if the compressor will start. Have you checked your refrigerant to see if it is at the proper pressure?
 
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Old 10-13-13, 10:09 AM
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Pressure are fine, freon level is also OK, produces cold air to the house. It is in excellent condition except the cut off problem at the first half second. I'll try to bypass those switches and time delay next time. I also noticed there was a spark from the contactor (looks like from one of the 24V contactor terminal) at the same time the contactor button pops out. 3 minutes later, contactor engaged again, no sparks this time. I replaced everthing except the control board. Can it be the problem ? I may have to replace it if nothing else can be done. (is there a simple way to bypass the control board, and connect the 24V directly to the contactor ?)
 
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Old 10-13-13, 10:25 AM
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This sounds like either a bad connection at the 24V contactor terminal(s) or a contactor problem. Because it sparked it sounds like a bad connection at the terminal. I would pull the wire off where it was sparking and make sure the terminal on the contactor is not corroded and that the female terminal on the wire is tight on that terminal. Also follow the two 24V wires from the contactor to where they are wire-nutted from the thermostat bundle coming from inside or connected to the terminal board at the condenser and check those connections. Inspect the thermostat bundle wiring between the house and the condenser for any possible damage caused by weedeaters, dogs chewing and etc. You could also ohm out the contactor to see if it is within specs. I don't believe it is a control board issue since you are getting the required 24V to the contactor. The high and low pressure switches should not be an issue since the pressures are good and the unit starts. At this point I would totally remove the time delay from the picture to see if that is the issue. A digital thermostat should already have the time delay feature. It can usually be set for different time off delay.
 
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Old 10-13-13, 10:25 AM
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When the unit gets 24vac it should do absolutely nothing for 3 minutes. That 1/2 second start up pulse is not good for your unit. I would check and make sure the thermostat has a delay built in and then remove the 3 minute timer.

Pressure switches have no effect on this problem as it shouldn't start in the first place.

I have a feeling that the 3 minute delay board needs the load of the contactor directly on it so that you don't get that 1/2 second stutter. If that timer board goes to an electronic board then that would be the problem.
 
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Old 10-13-13, 02:55 PM
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Thanks folks, I'll re-work the timer and the contactor connection again, or remove the timer all together and see what will happen. will report back.
 
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Old 10-17-13, 09:01 AM
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Problem solved, the 24V wire to the contactor is still tight, but the wire connector has some rust inside, it does not really look that bad. Anyway, I cleaned the terminals and replaced both wires with new connectors. No more problem after that. Can not believe those little wires gave me so much problem.
Thanks to all of you.
 
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