HELP! When I push in the contact relay the unit w

[jonmiles]

Hello and thanks for your help in advance. Our A/C stopped working and after replacing the contact relay and testing for 24 volts still can't find the problem.

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 contact relay, 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.

when the inside temp reached 76 and the inside blower turned off the outside unit still runs because I had a stick holding in the contacts. 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.

I checked for 24 volts at the contact relay and was getting 19 volts to ground which would drop to 14 when I push in on the contact relay. I replaced the old contact relay with a new one and it still does the same thing. I thought maybe the 24 volt transformer was weak so I replaced it and still had the same exact problem.

We know the thermostat is working and we have 24 volts inside so what would cause the contact relay not to engage when the unit is cooling just fine if I hold the contacts in ?

Remember the unit ran fine after the power was restored for 3-1/2 days and then when we had the brown out that's when things went bad.

Do you think the electric company may have had a surge and it caused the problem ? 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 all 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 including a wiring schematic.

Thanks in advance for your help.

Picture of Rudd Logo on unit, shows type of unit:

http://img15.exs.cx/img15/1711/PA040001.jpg

Picture of contact relay panel area with stick holding relay button:

http://img15.exs.cx/img15/6990/Ruud-Air-Conditioner-1.jpg

picture of wiring schematic from units side panel:

http://img15.exs.cx/img15/5434/Ruud-wiring-schematic.jpg

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

[LazyPup]

The machine runs okay when the contactor is depressed manually so we can be sure the problem is in the low voltage control circuit.

Normally the thermostate low voltage cable is connected directly to the low voltage solenoid coil on the contactor, however, some systems have additonal controls that are optional, such as low pressure cutout switches, high pressure cutout switches, delay on make timers, delay on break timers, etc.

Your schematic is showing the proper placement of a couple of those optional switchs.

Normally the Thermostat control cable uses a red and a white wire for low voltage control to the contactor, however it appears in your photo that the wire connected to the low voltage terminal is a heavier brown wire. No doubt that wire is one of the optional switches connected in series in the control circuit.

Some units have a manual reset high pressure control. Look for a reset button, usually on the outside of the cabinet near the point where the electrical cables enter the cabinet, or near where the refrigerant lines enter the cabinet. If you find a manual reset (REd Button) press the reset and try starting the unit again. If it still does not run you will have to trace the low voltage control circuit looking for the additional control switches. When you find a switch, temporarily disconnect one wire from the switch and measure the resistance across the switch. If you get full continuity, replace the wire and move on to the next switch, until you have gone through the entire low voltage section.

If you encounter a switch that is open (NO continuity) that is your defective switch.

[jonmiles]

Thank You very much Lazypup. This is what I have been looking for. I have posted this info. in 3 diff. HVAC forums and you are the first to come out and tell me exactly what I needed to do. I felt as if other people knew but they wanted me to jump threw a few hoops first. I know the HVAC pros need to make a living also but with the hurricanes we can't afford to spend another $500.00 right now if it's something I can do myself. Thanks for your help. [8D]

[Troy]

jonmiles,

Glad you found your answer. Welcome to the forum! Lazypup, you never cease to amaze me!

[jonmiles]

Thank you very much for your help Lazypup. I found the problem.

The high pressure sensor was zip tied together and damaged so I bypassed it. I then tested the other sensors and found the defrost sensor was bad. I bypassed it and ordered another one for 17.00. Everything works great now.

When I first started 3 days ago I had never worked on a A/C unit and now I feel pretty comfortable I can troubleshoot problems. All I needed was somebody to explain how the system works and once my brain started putting it all together I was fine. Lazypup did a great job explaining how things work as well as another forum where somebody posted the step by step breakdown that helped me understand it all. Once I read that, we were ready to troubleshoot.

I still can't beleive it is sooooooooo easy, now that I have done it.

I have a new contactor relay now because I replaced it before knowing how things worked but the old one had very worn shunts so it wasn't a total loss. And I have a new 24 volt transformer with inline fuse so we won't be burning up any more of those. But what newbie hasn't burned up a transformer.

Everything is clean and ready for another year.

Thanks again for your help.

[imeduc]

Dont forget the time delay for down here.


ED

My mistakes dont define me they inform me.

[LazyPup]

Bypassing the defrost sensor will get your ac up and running, but do not operate your heat pump in heat mode until you get that sensor replaced. It could lead to icing on the condenser coil and do serious damage to the compressor.

As was mentioned in the previous post, if you live in an area where the commercial electrical utility is often disrupted by storms or brownouts you should definitely consider installing a delay timer on the control circuit.

One of the greatest causes of premature compressor failure results from a condition called "short cycling". It is a condition where power has be interrupted momentarily and the compressor switches off, then instantly tries to restart while the internal refrigerant pressures are still high. That places an extreme load on the start windings of the motor and causes it to generate excessive heat.

There are two types of delay timers, delay on make,or delay on break.
Either one will work equally well, although most people prefer a delay on break timer.

Technically the difference is, a delay on break timer starts its count the moment the motor is turned off, and normally the time will have elapsed and the system will be ready for instant restart when the thermostat calls for the comdensing unit.

A delay on make timer begins its timing function when the AC is turned on and it delays the start for the preset time, thus when the thermostat calls for the condenser their will be a 90 to 120 second delay before it actually starts.

The timers usually are set for 90 to 120 second delay. In the event power is disrupted the timer prevents the unit from trying to restart for the preset time limit. That allows the internal refrigerant pressure time to equalize, thus reducing the start up load on the compressor. It also insures the start windings have adequate time to cool before a restart is attempted.

In operation the homeowner would never really know the difference unles you happened to be standing by the unit the moment its turned on, but most people prefer the instant on feature of a delay on break timer.

[jonmiles]

<<I bypassed it and ordered another one for 17.00. Everything works great now.>>

I actually picked up the defrost sensor tonight, they are fast. The warehouse told me to install it before I run the heat. Thanks for making sure though.


<<Dont forget the time delay for down here.>>

The unit already had one installed. Thanks for the tip though.

Thanks again

[jonmiles]

Mine must have the [u]delay on break </u>because it will not try to start if you shut it off and then back on. Even if you push in the contactor relay after shutting it off, the unit will not start. If you wait and then push in the contactor relay again after say 30 seconds(approx.) The unit starts up with no problem. Is this relay built into the comp. motor ? Or how does it work if you are bypassing all sensors by manually pushing in the contactor relay. I only know mine would not start unless I waited. I never tested for power to see how it operated while waiting.

Thanks

[LazyPup]

The delay timers are low voltage controls in series on the thermostate control cable.

If your compressor did not start when you manually depressed the contactor no doubt the problem was that the internal refrigerant pressure had not yet equalized, thus the load was too great for the motor to start.

[jonmiles]

Thanks, I'll tell the guy at the warehouse I need a delay timer.

He said, he would be glad to explain how to install any of the parts I buy. So I won't trouble you with the details of how or where to install it in line.

Thanks [8D]

[jonmiles]

Lazypup, It seems I still have a problem after installing the defrost sensor. For some reason now the fan will not work. It worked after bypassing the defrost sensor but now that it is installed again my fan won't work. I have been talking with a guy on another forum and he has been a lot of help like yourself so i was wondering if you would mind reading my post there and telling me what you think may be the problem. Thanks, it was getting hard to keep posting on 3 diff. forums.

Here is the direct link to the topic:

http://www.repair-home.com/dc/dcboard.php?az=show_topic&forum=9&topic_id=333&mode=full

[HayZee518]

Lazy is a well versed a/c tech. Also a well versed plumber. I am an electrician of 45 yrs plus. Not to step on toes, he knows a lot of theory and what works, does. I'll back him up 100% He is an excellant survice to this forum.

[LazyPup]

I have printed the picture of your schematic, then scanned it back into my graphics program to enlarge it. There appears to be a couple optional controls on the fan circuit that are difficult to identify from the schematic alone.

There appears to be a "component code" list on the lower left side of the schematic but it is cut off in the picture so the codes are not visible. If possible, take another picture of the schematic with emphasis on that component code list and email it direct to me-- LazyPup@yahoo.com

In the mean time, try bypassing the defrost sensor again. If the fan works, then you should be able to use the AC while we resolve this new problem. You just wont be able to run it in heat mode till we find out what the fan problem is with the defrost sensor in place.

[jonmiles]

I wasn't trying to say one person was better than the other HayZee518.

Only that I found somebody else on another forum who was willing to help and when I flipped a coin, decided to post on the other because the guy replied very fast and I was looking for answers very fast. They both gave very good information so I wanted to see if they could help me out some more together. If Lazypup could read the info. I posted on the other forum he would be up to date on what has been done and this would save us both a lot of time.That is all I was trying to do.

I know he didn't do that because he suggested I un-hook the defrost sensor again and run the unit that way until we figure something out. I posted on the other forum that the defrost sensor being a open sensor that I wired direct when removing the sensor caused the unit to go into defrost mode and the fan was still running because the thermostat was in cool mode or something. Now that I have installed the defrost sensor the fan will not run. So it won't do me any good to rewire the defrost sensor again. It seems that now the capacitor is bad because the fan won't work and is showing 88 volts on the fan terminal vs 341 on the HERM terminal and they used to be the same. So you see I wasn't trying to step on anyones toes. Only to save time......

Nothing personal, Lazypup has been very helpful and if he is a moderator for this forum and loyal to this forum that's great. I wasn't trying to steal anybody from this forum.

Sorry, I just wanted to make my intentions very clear. I have appreciated all your help.

I'll take a new picture of the wiring schematic Mon. and send it to you [u]direct</u>.Lazypup

cutting off the most important part of the wiring schematic ?
I thought all were the same abreviations and was in a hurry, didn't notice it until I started to crop the photo. Sorry

Thanks again.....ttyl