View Full Version : Power coming back on common
08-26-2011, 10:52 PM
I walked into a problem. A Hunter ICC clock with 32 zones. Zones 1,2,3,4,5,7,8,9,11,13,14 do not come on with the clock. When I put a multi-meter on the clock, there are multiple stations with showing power. Oddly enough, the zones that work, 6,10,12,15,16... do not have power. (as they should not) There are multiple common wires, 5, coming into the central wiring box. As I tested, one of the common wires had 25.7 volts coming through it. I realized this is why the zones on the clock were reading power. I am thinking I have a solinoid that has gone bad letting power through. Also, I have 3 Valve boxes under water. I pumped them out and pulled the wires up to dry. They appeared fine but...
So the question is...How would it be possible for multiple zones to want to fire, ie. the hot common?? Would one bad solinoid do that?? Would the problem only occur when the zone with the bad solinoid fires?? Appearantly not!! How can I locate which solinoid is bad without checking all 11 that are not working?? My brain hurts!!
Remove the zone wire from one of the stations that's got full time power and check it again. I've found that on some of the Hunter clocks, if the wires are stuck in too far they can come into contact with something inside the controller or module that is always hot. I know this is the case with the XC, not sure about the ICC, but if you remove a station wire, you can confirm that to be the cause or rule it out.
Also, Hunter modules do go bad. I've replace several PCM's because of similar problems, I wouldn't be surprised if that was the case here.
08-29-2011, 11:55 AM
Check the ohm readings with a decent multi-meter. Compare the reading from the suspected station against that of a confirmed operating station.
Typically the common wire becoming "hot", as you explain, is almost always caused by one of the multiple common wires leading into a defective station being wired onto the power leg by mistake. This is especially true when the moron who either installed or "repaired" the system before you ran out of white wire and substituted a different color, almost always red.
I have also seen where a previous contractor directly wired the common off of the neutral buss located in a A/C service panel then tied into the field common wiring. This caused all of the solenoids associated with that leg of the common to fry as well as an incredible power feedback directly into the controller. In this instance an ICC which incredibly survived for a year before burning up. When I metered the ICC I was receiving all sorts of wanky readings which I traced back to the A/C unit power source. The ICC was receiving 115 volts so when I opened the service panel I noticed the stranded wire touching the main buss leg above the breaker. The wire insulation had burned through and was completing the circuit causing this problem.
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