diagnosing defrost board, defrost thermostat

I have a Gibson self contained GQ3R heatpump that has a defrost problem. My question is, how do you diagnoise a defrost thermostat, and how can you diagnoise the defrost board, or put the board into the defrost mode without the defrost thermostat connected. I think the defrost thermostat is a thermistor, is that correct?
Many thanks.
Everett
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If you were a tech, you would know how to run it though a test defrost cycle. Just don't short the wrong terminals or you will be buying a lot more than a DF board..... even if the problem is *only* the DF board.
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wrote:

Thanks Steve for a great answer! Just for the record I was a HVAC contractor in the Nashville, TN area for 18 years and gave it up in 1989 for other interest. I know my way around the equipment very well but am not familiar with the newer "to me" defrost board and defrost thermostat. Almost every heat pump in that era used a different way to do the same thing and it wasn't integrated onto a single board. I can swap parts, but would like to diagnose before throwing parts at it. By the way the board is part# 624633
Many Thanks, Everett
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On 2/18/2011 9:55 AM, snipped-for-privacy@hughes.net wrote:

Suggest you stick with your other 'interest' and call someone who is qualified.
No offense.
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On Feb 17, 12:51 pm, snipped-for-privacy@yahoo.com wrote:

On every board ive worked on, there are self test pins that you jumper to put the unit into defrost initiation and defrost termination modes . Im afraid that there are so many boards out there that a Model Unit brand or part number on the board is of little help. Best thing is to either get a manufacturers checkout procedure sheet or find a local HVAC guy who has worked on these units who wont mind sharing his knowledge with you. In closing, oftentimes when you look at the board there will be 2 or 3 pins that are marked 'Test' near them --- these are most likely the test pins for sending the unit into defrost . I miss the old Ranco mechanical type Defrost Control that was simply to engage defrost as well as troubleshoot .. such is progress i guess. Regards.
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On Fri, 25 Feb 2011 07:53:28 -0800 (PST), " snipped-for-privacy@gmail.com"

Thanks for the reply, I found the answer on the Nordyne site. Nordine is the manufacturer of the Gibson line. There have been a bunch of upgraded defrost boards since the date of manufacture on my unit, but I think the test method is at least the same since my board, as the test method I used was for a newer unit. There is an area at the lower left of the board that has three terminals. They are marked ( T2 - Def - test ). Using these terminals you put a jumper between T2 and defrost with the unit in heat mode and running, then jump between test and C to enter test mode, removing test - C connection as defrost test starts. To stop test remove jumper between T2 and defrost.
Your right about the old Ranco board, I use to work on all brands and would scratch my head on many ocassion wondering why every manufacturer would do the same thing a different way,
Best Regards
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On Feb 25, 12:45 pm, snipped-for-privacy@yahoo.com wrote:

Glad you got your answer. Actually, I wasnt referring to the Ranco Defrot Board, but, the old Ranco E15 mechanical type Defrost Controls as thus : http://thermatixsupply.com/index.php?dispatch=products.view&product_id=30821 . It was nice and simple and you could run the Heat Pump Unit into and out of defrost cycle by manually turning the Timer .
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