Finding common wire on old MOODY controller

[thew60]

Good morning. I am looking to upgrade my nearly 50 year old MOODY mechanical controller.
It is a 6 zone controller with 4 in use. When I expose the wire panel, there is a "H" and "N" presumably HOT and NEUTRAL for the direct AC power. There is wiring going to zones 1-4 and a yellow wire in zone 7 (only 6 zone controller but has a 7 and 8 slot)
I apologize in advance for failing to provide a photo...

There is no "C" slot labeled, only "H" "N" and 1-8, even though this is a 6 zone controller.

Any input would be greatly appreciated.

Thank you

 

[WorthFlorida]

I think I've seen one, are there dial wheels, one for each zone? I'm guessing that the zones are 24v. A picture would help so again I'm guessing that the connection is a terminal strip. Possibly the AC power and the zone outputs are on the same strip or two strips, AC on one and zones on another.

Question on the numbers, Zone 7 is probably is the common, 8 could be a relay start lead for when used with pumps. You'll need to open a valve cover or dig where there is one and look at the wires on the solenoid. If one wire is yellow and it comes and goes from the solenoid, that is your common. Another way is with a voltmeter, turn on zone 1 and measure the voltage between 1 & 7. If there is 18+ volts then 7 is the common. Check the voltage at zone 2 and there should be no voltage, then switch on zone two. Voltage between 2 & 7 should be the same as with zone 1.

What type of controller are you planning to upgrade to? I would recommend a Rain Bird with WiFi.

 

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[thew60]

Thank you for your reply. I found the COMMON which was the yellow on zone "7"
now for another question- my zone "3" is dead. I tested the voltage at the controller and zone 3 is putting out no voltage when it is actuated.
Would it be easy enough to move the zone 3 wire to zone 5 just to confirm that the zone does actually work? Want to do this before I commit to the new controller.

 

[WorthFlorida]

If the zone wire was attached to terminal 3, remove the wire and check again. The solenoid could have a short, but swapping zones is perfectly fine. A short could have damaged the zone at the controller but with this mechanical unit, maybe a set of contacts burned or worn out.

Do a resistance check to the zone 3 solenoid. The reading can be anywhere from 20-60 ohms but usually it’ll be around 25 ohms. If the other solenoids are the same they all will return the same value.

 

[thew60]

Thank you for this great information. Of interest, is that I also checked the voltage to zone 3 DISCONNECTED from the solenoid and got ZERO. I also replaced the solenoid still with no luck. So by process of elimination, I believe that zone 3 is dead. Your information regarding the fried zone on this vintage mechanical unit makes plenty of sense.

I am going to miss this thing, an all metal, mechanical beast, but 40-45 years is a good run for a controller.

 

[thew60]

UPDATE still having an issue.
I replaced the solenoid on zone 3.
I purchased and installed the new Rachio 3 controller .(was planning on doing that regardless of the outcome of this situationI )

Zone 3 still dead however can open the zone with the valve screw .

Suggestions please ?

 

[WorthFlorida]

With the new controller you should have 24v’s. With the wire disconnected at the controller put an ohm meter on it. If it is open the wire is broken somewhere to the solenoid. Could also be the common wire to that solenoid. Is the common wire a single wire at the wire nut or is it combined with a wire passing through.