bad control board or what

[j carter]

came upon an airhandler furnace today model# GMPO75-3 i belive its a goodman not 100% sure. but my problem is that i can't get 24volts to contactor coil to the condenser.my first check was the thermostat,when calling for cooling thermostat is passing power there is 24volts at the secondary of the transformer,blower motor runs,this unit has a printed circuit board.terminal on board that connect to 24volts at contactor coil are r-and-g from those terminal on the board i get 24volts but when i connect wires nothing happens and yes i did ohm out wires no breakage.but when i connected wires from the contactor coil to secondary of transformer the condenser came on, is this board bad or what.

[2hot2coolme]

Is it an air handler or is it a furnace??

[grumpyyank]

R and G Wires should be connected to Y and c. gis the fan circuit r is the hot side of transformer. What color wire is connected to y at t-stat if it is yellow find yellow wire at furnace connect to one wire going outside connect other wire to common of transformer "c" terminal. Bingo it runs.

[Jultzya]

Originally posted by 2hot2coolme
Is it an air handler or is it a furnace??

You've never seen a GMP? Are you serious?

[Jultzya]

Originally posted by grumpyyank
R and G Wires should be connected to Y and c.

Are you sure? If they are that would be a problem. :D :p

[pulse21]

I think the board is fine. Check Y to common at furnace if you hve power there problem is not stat or wire from stat. If the outdoor unit won't run it usually has nothing to do with the control board. Seek professional help!!!!!!!!

[Jultzya]

Originally posted by j carter
is this board bad or what.

Board? No, not since the blower is running.

Or what? Yes, you need to verify whether you have 24 volts at Y (which you don't). Beings you tested (y & c) by connecting directly to the transformer and it runs. The real question is why don't you have 24 volts on Y?

[inturmoil]

Are there any high or low pressure switches? Is there power from Y to C at the condensing unit? Important questions for a service tech. . .

[Jultzya]

Originally posted by inturmoil
Are there any high or low pressure switches? Is there power from Y to C at the condensing unit? Important questions for a service tech. . .

Re-read the original post. He says the condenser runs if he connects the Y & C to the secondary 24 volt power.

Therefore, the pressure switches are out of the equation (even if they do exist). And there is no power at Y & C at condenser, because it's not running.

[pulse21]

sounds like could be tsat or even a float switch or condensate pump float.

[dec]

knock it off knuckleheads ...its a diy. As basic as that is he can ask his boss. Then his boss will question why he has him out there, Which he should

[Edited by dec on 10-04-2005 at 12:58 AM]

[Jultzya]

Originally posted by dec
knock it off knuckleheads ...its a diy.

Really?

He starts out by saying "came upon an airhandler furnace today".

In this (http://www.hvac-talk.com/vbb/showthread.php?threadid=67345) post he posted "I am having a problem with a old whirlpool gas furance".

In this (http://www.hvac-talk.com/vbb/showthread.php?threadid=73402) post he posted "I recently serviced three marley cooling towers".

In this (http://www.hvac-talk.com/vbb/showthread.php?threadid=77838) post he posted "i am looking for a break down for a copland compressor the model # is erfi-0310-tad".

In this (http://www.hvac-talk.com/vbb/showthread.php?threadid=79455) post he posted "need understanding of the purpose of the chill water valve on a airhandler".

In this (http://www.hvac-talk.com/vbb/showthread.php?threadid=80084) post he posted "went to service a refrigerator today".

In this (http://www.hvac-talk.com/vbb/showthread.php?threadid=80314) post he posted "Today i came upon a water chiller model# M-50-rfc".

Do you really think DIY'ers work on very many chillers? Or have this variety of equipment at his homes?

[mark beiser]

Originally posted by j carter
terminal on board that connect to 24volts at contactor coil are r-and-g from those terminal on the board i get 24volts but when i connect wires nothing happens and yes i did ohm out wires no breakage.


Connecting the 2 control wires from the outdoor unit to R and G on the control board won't do anything for you because there is not a good enough path to common through the G terminal. A meter will show that you have 24v, but you can't run anything with it because the path to common is through transistors. (Overly simplified, but it sounds like you probably wouldn't understand the real explanation)

The 2 control wires from the outdoor unit whould connect to the thermostat wire that is connedted to Y at the thermostat, and to the 24v common from the control wire.
There is no Y connection on the control board for the GMP furnaces. The common wire off the control board should be the blue one.

Check to make sure you have 24v between Y and common when the thermostat is calling for cooling...

If you are a DIY'er, please get a pro to look at the problem before you cause damage to yourself or your property.

If you are a "pro", please get help from someone more qualified, and/or get some training in basic electrical troubleshooting.

[Black Adder]

Just a dumb question but do you have RH and RC jumped at the thermostat. If it has these connections you won't get any power down to the board if you are not sending 24v down the RC for AC. AHH now I'm confusing myself, just check to see that there is a jumper on RC,RH in the tstat if it needs one.

[troyorr]

Had a similiar problem last winter. Unit flashed open limit. I checked all limits and everything was okay. Put back together and then I would get a failed to sense flame. After about what seemed like 1000 hours later, I discovered I wasn't getting full contact through the connector on the control board. When the molex connector was pushed onto the socket on the board, one of the pins was loose and being pushed out of contact. Don't think that wasn't a head scratched.

[krd]

The easy way to verify: 1st jump the yellow(cooling)to the g terminal in the t-stat. If the if the outside unit runs with the inside blower running then the relay in the stat is bad. if it doesn't go jump the same terminals in the furnace and see if the unit runs if it does, you have a break in the wires going from the t-stat to the furnace. I really don't see whether if its an air handler or a furnace it makes a difference. Your in cooling mode.

[2hot2coolme]

Originally posted by jultzya

Originally posted by 2hot2coolme
Is it an air handler or is it a furnace??

You've never seen a GMP? Are you serious?


I know it's a furnace, just wondering why it's listed as an AIR HANDLER/FURNACE, there is a difference ya know...thought it was a DIY also. SO....:p

[Jultzya]

Originally posted by 2hot2coolme
thought it was a DIY also. SO....:p

Rookie! :eek: :D :p

[j carter]

now first things first,never said i was a service tech or worked on a service truck.my back ground is in commerical only five years experienced no residental experience.and yes i do need more training but i know everyone did'nt get where they are just over night,i work in a commerical building not trying to make myself seem like something I'm not.
yes i am a building engineer trying to increase my skills so just keep it coming.

[Jultzya]

Originally posted by j carter
yes i am a building engineer

Boy have you just screwed yourself on this board.

I would have never admitted to that! :p

And to think I was on your side! :D

[inturmoil]

Oh, an engineer. . .who can't spell or use correct punctuation. . . .can't even correctly spell a contraction. . .I'm shocked!

[Twilly]

Give the guy a break, replace board, stat and all low voltage wiring. This should take care of the problem, hey we need sanitary engineers.

[krd]

I think we need to ease up a little bit. Nobody knows everything. If they did you wouldn't need discussion boards like this one. The idea of the board is to help educate and to solve problems not to intimidate or critize. Sometimes we all get carried away. Only truly stupid people are afraid to ask Questions. I've been around the block so to speak and have seen well seasoned maintenance men ask a question that I just shook my head on. And I have been in the position more than once where several of us where scratching our butts over a problem and the stupid janitor looked at us and said did you check this, thats what use to act up years ago,and he was right on the money. I,ve been called everything from Dx genius to stupid -ss in the same sentence. So in retrospect I think we need to be a little bit more open minded. Now I do 95% residential work but in the past before I got downsized I was the engineer in charge of the engineers and I didn't see a problem with the question.