Air Conditioning - A/C works when I hold the reset,but stops when I release it ?

I'm new to the DIY forum and would like to say Hello ! I've noticed a lot of great replies from people and hope someone can help me out as well.

Our Ruud A/C heat pump unit has been working fine all year here in FL. We had it serviced last fall and everything checked out fine. Service company said the unit was about 12 yrs. old.

We have been without power for 6 days from the hurricane and now have elec. again. The A/C was working fine prior to loosing power and has been working fine Fri./Sat./Sun. after power was restored and then Monday afternoon stopped cooling. The blower inside is working and the thermostat is new so I checked the unit outside only to find it was not doing anything. I checked for power and it has power at the unit, I then pushed in the contact relay button and the unit started. I released the button and the unit stopped. I waited about 2 min. and then pushed the button again and wedged a stick against the button to hold it in this time and the A/C has been cooling great. The big line is sweating cold and the small line is warm/hot. The fan outside is working fine. I set the therostat to 76 when the inside temp was 80 and it cooled the house down in a couple hours with an outside temp in the high 80's.

But when the inside temp reached 76 and the inside blower turned off the outside unit still runs. I assume the reset button or switch is the cause, do you think the switch is bad ?

Also I can turn the thermostat down from 76 to 74 while the outside unit is still running and the inside fan comes on again and continues to cool just fine.

Do you think the electric company may have had a surge and it caused the contact relay to go bad ? My battery backup unit came on in the computer room and said there was noise on the line and this was about the same time the A/C stopped cooling. Any help would be great. I don't know much about A/C but with a little help can prob. figure it out. I don't know the A/C tech terms or names of parts so if you could please explain in simple terms that would help.

I have included some links to pictures of the A/C unit which will show the relay I'm talking about. Thanks in advance for your help. :) :confused:

Picture of Rudd Logo on unit:
http://img43.exs.cx/img43/6020/Ruud-Achiever-9-high-effici.th.jpg (http://img43.exs.cx/my.php?loc=img43&image=Ruud-Achiever-9-high-effici.jpg)

Picture of contact panel area with stick holding relay button:
http://img43.exs.cx/my.php?loc=img43&image=Ruud-Air-Conditioner-2.jpg

Another close up picture of contact relay:
http://img43.exs.cx/my.php?loc=img43&image=Ruud-Air-Conditioner-reset-.jpg

picture of wiring schematic from units side panel:
http://img43.exs.cx/my.php?loc=img43&image=Ruud-wiring-schematic.jpg

Thanks again for your help, maybe I can return the favor in another topic. ;)

Can be wrong here but I think I see heatpump here. I wonder if the brown out the ,off and on got the control board in the outside unit there. Id say ok to put the stick in till you can get it worked on but dont run it like that with the blower off inside at all. Does the coil there get 24 volts?That tstat new ??? It had been running with it before this???Down here with FPL for power ask the tech to put a time delay in there for the compressor so it will go down on a brown out are just a on off of power. I have had 220v down to 190 V here.

ED :eek:

Yes it is a heat pump unit.

Yes the thermostat was new in fall of 2004 installed by Tech

Yes the area has had brown outs

Does the circuit board control the switch where stick is holding the reset ?

CLICK ON LINK TO SEE PHOTO

http://img13.exs.cx/img13/4090/curcuit-board-close-up.jpg

circuit board photo link (http://img13.exs.cx/img13/4090/curcuit-board-close-up.jpg)

Thanks Ed Imeduc

A picture [s] is/are worth a thousand words or more? The device you are holding in with the stick is NOT a reset. It is the compressor contactor. Look on the wiring diagram, see the HPC? [High Pressure Control] That IS a resettable control and is usually a little red button sticking out at the base of the unit near the pipes that enter/exit the unit. Ed is right, take out the stick before you burn up the compressor. If you can read the schematic, you can check the circuits with your voltmeter. See the YL and BR wires on the diagram? See if you have 24 volts there [iow- one meter lead on YL and one on BR] when the thermostat is calling for cooling. If you're not comfortable testing live circuits, then call a tech, but please pull the stick before you cost yourself mucho $$$$ needlessly. Thanks.

I have been researching A/C info. since I posted this topic and realized the part I was calling a reset is in fact a contact relay. I tested this relay for 24 volts at the coil and found 19 volts not 24. I also tested to ground and not YL and BR at the same time which may have made a big diff. :rolleyes:

This is why I posted the pictures, my lack of A/C parts knowledge makes it hard to explain what a person is trying to explain :D

I figured replacing the contact relay wouldn't cost that much so I went down to the local warehouse and for less than 20.00 picked one up. After installing the new part exactly the same way the old one was installed I powered everything back up and guess what, nothing but the inside blower working just like before. I pushed in the contacts and the unit worked just like before but when I released the stick they popped back out. So I was back where I started and 20.00 lite in the wallet.

I figured at this point maybe it is the transformer since I was getting 19 volts when testing to ground and the coil requires 24 to energize ? So I run back to the supply house and spend another 15.00 for a 24 volt transformer. Install it exactly the same way the old one came out and guess what ?

You guessed it, the contact relay still would not engage. I tested the volts and found 24 this time but the contact relay still would not engage.

I'll wait until this weekend when I have more time and hope that between now and then somebody can help me out or I'm calling the Tech.

I do service work and charge the same as the A/C service guys do so it's not that I don't think they are worth the money. I just figured if a person can learn something new, he would be that much better off the next time something happens.

Thanks for the help BigJohn1

By testing to ground, you read thru the coil on the contactor which is why you have voltage on both sides. Basically what you need to know is whether you're getting a closed circuit from the thermostat to start the unit in the first place. If you have 24 volts on YL and BR when the thermostat is set for cooling, the problem is in the outdoor unit. If not, the problem is elsewhere.

BigJohn1:

I took a picture of the thermostat to make sure we are on the same page. The picture shows B and y1 as the wires I understood you to be referring to.

Are these the wires I am to test at the same time with the voltmeter ?

You will notice that B has a red wire and not a brown wire. This was installed by the A/C service tech 1 year ago.

Here is the picture link: http://img8.exs.cx/img8/1291/Thermostat-brown-and-yellow.jpg

I hope these pictures don't take long for you to download, I didn't want to compress them much when we are depending on them for info. :)

At this point the only picture I have not posted would be the wiring inside the blower unit where the 24 volt transformer etc. etc. is located. If the thermostat was not the wires you were talking about maybe one of the other pictures will show what you were referring to. I did have a picture of the wiring schematic which would show the wires you are talking about.

Thanks again for your help.

Test brown and yellow at the contactor @ the outdoor unit. The one you was pushing in with a stick.

If you have 24v with your probes on the coils spade connectors then the contactor is bad. If you don't have the 24v then follow the low voltage wires and check them for any safeties or time delays they may run through.

Thanks, I'll check that........

You said the inside fan came on. So here we still need AC for the time try and run the two wires that come from the home to the condenser the 24 volts and just put them on each side of the contactors coil there . Then the ac should run when you call for it from inside. jump around the defrost board for now. But see how your 4 way valve is wired here .If it fails on heat or on cool?????

ED ;)

Where is the defrost board ? Is it in one of the pictures attached to my original post so you can point it out ?

What 2 wires do you want me to remove from the defrost board and connect to the contact relay coil (on each side).

The one yellow wire is already connected on one side from what I understand and the other brown must come from the defrost board you are talking about. Is this correct ?

4 way valve ? what is a 4 way valve ?

Sorry but I don't know that much about house A/C. But you already knew that huh!

Thanks again, we are getting closer. I hope !

two wires that come from the home to the condenser the 24 volts and just put them on each side of the contactors coil there . Then the ac should run when you call for it from inside. jump around the defrost board for now. But see how your 4 way valve is wired here .

ED ;)

Thanks for everyones help.

When I started a few days ago I had never worked on a A/C unit before and now I understand it much better.

Funny how something you once thought was so complicated becomes so easy after somebody explaines how it works and how to troubleshoot the problems. I wouldn't claim to be a tech by any stretch, but I won't be asking what a contactor relay is or 4 way valve, pressure sensor, circuit boards,transformers etc.

The problem ended up being a defrost sensor which I bypassed for now. I have the new one which will be installed before I need the heat setting.

I now have a new contactor relay installed which should be more efficient than the old one which had a lot of build up on the shunts, so it wasn't a total loss. And if needed I now have a back up contactor relay : )

Also a new 24 volt transformer with a in line fuse so we won't be burning any more of those up.

I also bypassed the high pressure switch which somebody had zip tied together from past service work, so that's one less sensor to give me problems in the future.

Everything is clean and working great again. Thanks again for your help.

Suggestion: The next time somebody ask about a problem and supplies the amount of information that I did with pictures. I would hope that somebody could tell them how to find the problem step by step,rather than give them hints. Anybody that does HVAC work should have known, considering how easy it was. I don't want to sound ungrateful but this should have been a VERY easy question for any HVAC person hint :( hint.