Heat pump clicking during defrost cycle

Old 12-07-03, 04:41 PM
Visiting Guest
Posts: n/a
Question Heat pump clicking during defrost cycle

My heat pump outdoor unit has clicked intermittently during defrost cycles for a few winters. I am finally serious about repairing it.

I have a good idea of how it should work, thanks to several threads in this forum, and from the wiring diagram I found on the Payne website (I have a Payne 810AJ030-C outdoor unit).

Here are some specific questions...

1) Which way should my defrost thermostat work? Should it be open or closed when the coils require defrosting? I've attached symbol of the defrost thermostat from the wiring diagram at the bottom of this note. Or you can try this link: http://www.trainweb.org/roc/pix/tmp/dft.jpg

2) About what temperature should the defrost thermostat change state? During my testing midday today, the thermostat was closed the whole time. Ambient temp was 35-40 degrees F.

3) Does "test" mode do anything more than speed up the clock? That is, should the defrost thermostat play its normal role in determining whether a reversal actually takes place, or is it ignored in test mode?

Thanks much.

Last edited by cclshome; 12-08-03 at 02:52 AM.
Old 12-08-03, 09:58 AM
mattison's Avatar
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,547
Received 0 Votes on 0 Posts
According to the diagram that's a normally open switch and would close on temprature drop.

What kind of click is it? and can you pinpoint where it's coming from?

It wont go into defrost until below 32 and then it's usually on a timer basis, like every 60 min or 45min. The circuit board on the outdoor unit may have a seeting for this.

Not sure about your test mode.
Old 12-08-03, 11:32 AM
Visiting Guest
Posts: n/a
Thanks for the two answers. My defrost thermostat was closed when the temp was well above freezing, so I will replace it.

The loud clicking happens about 2 times per second during defrost cycles. The loudest noise is definitely coming from the reversing valve solenoid. It is being triggered by a quieter simultaneous clicking of the control relay on the defrost board. (I am thinking the problem is either the defrost board or the defrost thermostat, or both, since the reversing valve solenoid worked fine in reverse mode when cooling all summer.)

Can anyone offer an answer to question #3?

Thanks in advance.
Old 12-08-03, 12:48 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,386
Received 1 Vote on 1 Post
Exclamation 4 way

Most units are set up that the 4 way is in heat mode, and pulls in in the A/C mode. The thinking here is that if it fails you will still have heat all the time ED
Old 01-02-04, 08:57 AM
Visiting Guest
Posts: n/a

I believe I have fixed my problem. Here's some info for future reference, based upon my studying the wiring diagram and measuring voltages going to and from the defrost board over several hours.

The fast-clicking sound occurred whenever the unit tried to perform a defrost cycle. The clicking sound was coming from the reversing valve solenoid. (The unit clicked last winter, and cooled fine all summer, so I believe the reversing valve itself is okay.) I believe the clicking was caused by weak or failing circuitry on the defrost control board. Each time the board tried to run a defrost cycle, the driver circuits apparently were not strong enough to energize and hold the reversing solenoid. And this was an intermittent problem; sometimes defrost cycles worked fine, and sometimes it clicked.

Although I did not suspect it was failing, I first changed the defrost thermostat, since it was available locally, relatively inexpensive, and easy to replace. But it did not fix the problem.

Second, I replaced the defrost board. I found an exact replacement from an online parts guy in Michigan at reasonable cost. It has worked flawlessly for two weeks so far. I have declared the problem to be fixed.

Thanks to the other members for posting answers. FYI, Here are what I found to be the answers to my original questions...

1) The defrost thermostat on this unit is open at warm temperatures, and closed when cold.

2) My thermostat closes somewhere below freezing, and opens above 80 degrees F.

3) "Test Mode" on this unit appears to do nothing more than speed up the defrost cycle clock. In test mode with my defrost thermostat closed, the unit performed brief and frequent defrost cycles. In test mode with the defrost thermostat open, the unit did not perform defrost cyces.

Thanks to everyone who posts to these forums. I found several appends about defrost problems and gained confidence that I was on the right track.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: