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kent.siems · Aug 16, 2011, 10:21 AM

Is there any simple way to test the blower unit's circuit board? It looks fine but my contactor won't pull down when it receives 24 volts on its coils. I don't know what else could be wrong but I don't want to buy a new circuit board if it is still good. Thank you.

hvac1000 · Aug 16, 2011, 12:48 PM

(((It looks fine but my contactor won't pull down when it receives 24 volts on its coils. I don't know what else could be wrong but I don't want to buy a new circuit board if it is still good. Thank you.)))

If the contactor is getting the necessary 24 volts to the contactor coil and the contactor will not activate then more than likely the contactor coil is defective which in most cases means that you will have to replace the contactor itself.

kent.siems · Aug 17, 2011, 02:19 PM

HVAC1000 - Thank you for your reply. I've already replaced the contactor. If you have the time, could you please read my other post which is at "https://www.askmehelpdesk.com/heating-air-conditioning/hvac-outdoor-unit-contactor-wont-pull-down-592590.html" It will explain what I have done so far and why I think I may have to replace the circuit board. Thank you. Kent.

Stratmando · Aug 17, 2011, 07:01 PM

Kent, I haven't read your other post, and if like hvac1000 is saying, if you have 24 volts to the contactor coil and it is not pulling in, IT IS bad.
Verify you have 240 Volts AC Into Contactor and see if you have 240 volts out when 24 volts is applied to the coil.

hvac1000 · Aug 17, 2011, 10:58 PM

Lightening can and will do strange things. If you really have 24 volts across the two low voltage coil wires then the contactor for the unit should pull in. If not then you really do not have 24 volts there OR the contactor coil is defective. Now I have seen cases where you can have a what I call GHOST 24 volts. That is it will show on a meter but when you try to use the circuit (IE activate the coil)The voltage disapears since it has a weak ground side or other issues and YES this type of situation can be caused by lightening or other electrical problems.

Try this. Hook your meter across the 24 volt wires as if to test the circuit then activate the unit. You should see 24 Volts showing at the coil and the coil should also be pulled in activateing the contactor. If the 24 volts disapears and coil does not pull in causing the unit to operate then you will need to tracethe 24 volt control circuit back further. But do not replace anything until you do this test. Report back with findings

kent.siems · Aug 18, 2011, 09:55 AM

Stratmando, thank you for your reply. I have replaced the contactor and it still won't pull down. Please visit my other post as it gives more details as to the things I have tried. The most perplexing to me is that if I ground the contactor's coil from the exit side of the coil while the input side is charged with 24 volts, the contactor will pull down by itself. Thank you. - Kent

Stratmando · Aug 18, 2011, 10:10 AM

I have read both post and if you have 24 volts to the contactor coil and it doesn't energize, It is bad, physically binding or froze, or maybe you have a contactor with 120 volt coil?

Stratmando · Aug 18, 2011, 10:15 AM

I have read your other post, wonder if you saw mine:
The transformer should not be grounded. Sounds like 1 side shorted and broke. Check the 2 contactor coils wires for voltage, check the color of these wires and physically follow the wires, hopefully it is all in conduit, and check for the 24 volts at the board where the 2 contactor wires are, disconnect if possible and check for 24 volts between the 2.
Then verify neither of the 2 controls wires is grounded, and then be sure both are intact. Reconnect, now if you have 24 volts at board, you should have 24 volts to coil with no connection to ground.

hvac1000 · Aug 18, 2011, 12:17 PM

I really hate this new setup on this board. That is why I stopped posting. To hard to track for me.

kent.siems · Aug 18, 2011, 01:51 PM

ALL - Please visit my other post as it is the same problem just worded at a differnet angle. It has more details. It is at https://www.askmehelpdesk.com/heating-air-conditioning/hvac-outdoor-unit-contactor-wont-pull-down-592590.html"
I also posted photos on my Facebook page which you can see at http://www.facebook.com/media/set/?s...52907ee&type=1 .
Thank you to all who have posted. I appreciate your help and hope to see you on my other post. We'll get this figured out and I'll let everyone know how it was done, even if I have to pay somebody to fix it, (once I get a job). Kent

Stratmando · Aug 18, 2011, 04:02 PM

I DON'T WANT TOO SCREAM, SO I WON'T.
What have you determined by my earlier post, There is nothing I need to read, did you do the above?
Can you tell anything but refer to what we know.
Need Feedback? Thanks

kent.siems · Aug 18, 2011, 07:27 PM

Stratmando, Thanks for not screaming. I'm from Iowa so I don't think I'd hear you though. It's been raining and lightening here lately so I don't want to do anything with the unit until it clears so hopefully I'll get some of these suggestions knocked out tomorrow. I'll take good notes and follow the directions closely and then I'll post my findings. Thank you for your assistance and for your patience. - Kent

kent.siems · Aug 18, 2011, 07:51 PM

HVAC1000, as I said in my post to Stratmando, I'll be trying all of the suggestions I've been given tomorrow and get some feedback to everybody. Thank you for your input and patience. - Kent