Clicking contactor on air handler

billybobjoe1127

I have had two different HVAC companies and several techs look at my system to try to troubleshoot my problem, they all had different answers. And I'm tired of hanging parts trying fix the problem. I have  Trane Heat Pump with an American Standard air handler. I have went through three contactors on the furnace (air handler) in the last couple of years. They start clicking at five to ten second intervals, usually early in the morning, them start buzzing until the contacts are burned up. Parts that I have replaced already as per their suggestions are defrost timer board on heat pump, both sequencers on heat banks, and thermal sensor. Cleaned blower housing, and replace filter every two weeks.  Checked charge on heat pump. Replaced thermostat with digital one. Still no help. I am not a professional, but can figure out most problems, but this one is driving me nuts. I am not a rich man, and can't afford these guys charging $ 100.00 per trip to suggest more parts. Any ideas would be greatly appreciated. 

Wayne_16

Has the supply voltage to the contactor been measured while clicking?

Measure the supply voltage to the contacter coil.  If the voltage is erratic or less than 20-21 volts the coil will be energized then de-energized  then energized again. 

May need to use a analog meter to see the voltage fluctuation.  Digital meters do some averaging to show a value on the scale.  (Sorry I know others know exactly what is happening internally in the meter).  The point is the digital meter may not show the voltage drop if a relay or electronic control board are controlling this relay. 



If the voltage is erratic, then it is a matter of locating the culprit and making repairs., wiring transformer, supply voltage to the furnace, thermostat wires, thermostat, limit controls, etc.  Could be a bad ground someplace.

Here is a excellent case of following the current path to locate the fault, rather than hop-scotch testing.  Place one meter lead at the transformer neutral.  Start at the transformer 24 volt terminal with the second lead, test each wire/component in the order of the circuit to identify the fault.  Do not overlook anything or assume something is okay.  This is a time where a temporary jumper with alligator clips comes in handy.  The jumper can be used to verify a suspected wire/component.  Remove the jumper after testing.  Do not leave any jumpers across limit controls.



Thanks, Minnesota Wayne

Techman

Clicking

contactors are not good . 1st ,is to check the low voltage at the contactor coil upon start-up.It should be 22-27 vac. If it is lower ,say 18-21vac,then check some of the following.What is line voltage  reading on the load side[ towards the compressor } of the contactor upon start-up.If line volts reading drops ,so does the low volts.If line volts stay normal ,then check the low volt xformer to see if it is wired properly. You need to know the hi volts in the house and match the hi volt connections of the xformer to the house volts. A house w/ a 208 vac supply and a xformer wired to the 230-240 vac tap will cause this type of complaint.

Coany

some things to try

 what exactly is drooping in/out in response to the clicking?

 does the relay drop in/out in emergency heat position, try it and see

is the fan dropping in/out with the clicking, try using the fan "on" position.

put  only one screw in the cover so WHEN ITS happening you can open it quickly and listen closely to which relay is clicking in/out

once you decide exactly which relay is dropping in/out

look hard at the wiring diagram on the door

decide what that relay is controlling

decide where the control signal for that relay comes from.

 to me; what your describing sounds like a control signal problem

 semi-shorted wire or poor connection somewhere in the 24v circuit.





 then follow the advice given above

geno54

Some things to consider

Some not so obvious things to consider for chattering contactors

Poor solder connections on control board

Loose screw terminal connections

Poor splice connections

Pinched wires Possibly when stapled

Wires laying on hot water or hot gas pipes and grounding out

Wires chaffing on metal



Plus all the advice above, on finding the voltage drop

DanCanDo

Check Thermostat

I've been finding my fair share of "chattering" controls as a result of "Power Robbing" Thermostats...if it's electronic and doesn't require a Common or batteries, beware.  Jump it out and see if the chattering stops.