My parents (both over 80) called to tell me that their A/C wasn't cooling their house. I went over and took a look - the fan on the outside Rheem unit wasn't turning.
Read other posts on this forum and did the stick test - had someone turn the A/C on in the house, and I pushed the fan blade with a stick, and the fan started and started cooling the house (compressor seems to work, and the fan blades turned pretty freely when the unit was off).
Symptoms all pointed to a bad start capacitor based on what I've read here yesterday and Friday. The old cap had a little hardened leakage but wasn't bulging or distorted. Went out and bought a same-spec replacement start capacitor for about $30 and installed it, connecting the leads the same.
Expected the A/C to be fixed and start up. Didn't happen - the fan didn't move, and wouldn't start until I pushed it with a stick again. The fan started again and the A/C was cooling the house inside. I thought maybe the new cap needed to some time to charge up.
Ran the A/C for 45 minutes, then turned it off, waited 5 minutes, and turned it back on again. The fan still did not start. This time however, even pushing it with a stick wouldn't get it started. The fan blades did seem to feel a little harder to push this time, but it was not as if the fan motor was significantly seized up or anything.
Not sure what to try this time since the original symptoms seemed to point to a bad start cap. There is a run cap in the unit, but other than a slight coating of rust on the top, it doesn't look like it's exploded or anything like that.
I was thinking of putting in a new run cap, but thought maybe it is the start relay. How should I check the relay and anything else? I have a digital multimeter and can do the basic measurements.
The Rheem unit is about 6 years old and of course, now out of warranty.
My next steps would be to replace the start relay, run cap, and lastly the fan motor, kind of in terms of increasing component part cost.
Any ideas would be appreciated. Luckily we have had some rainstorms here this weekend so it's under 75-80 degrees in the house now. Thanks in advance.
(One last thing - the new start cap has the same spec's as the old cap down to the MFD range and voltage, but did not have a resistor bridging the two contacts like the old cap. Could this be a problem? The resistor did seem to be a little burned on the old cap, too.)
Photos of Rheem control electronics with original start cap in foreground, close-up of original cap, and close-up of new cap:
http://s764.photobucket.com/albums/x...t=PICT2741.jpg
http://s764.photobucket.com/albums/x...t=PICT2745.jpg
http://s764.photobucket.com/albums/x...t=PICT2747.jpg
The start capacitor does not wire to your fan motor. It only serves the compressor. It will be the capacitor or fan motor (and capacitor).
You did need a start cap as well though.
Hey, Houston204, thanks for the reply, but if the start cap is not wired to the fan motor, why do I keep seeing advice posted everywhere about doing the stick test to push-start the fan motor, and if that gets the fan going, then the problem is the start capacitor?
I looked at the wiring diagram from the manual I found inside the condenser unit, and it shows the start cap wired to the Herm and Com contacts of the run capacitor. So does the start capacitor give an extra boost to start up the fan motor through the run capacitor, or is it all up to the run capacitor to get the fan moving and stay moving?
Should I try replacing the run cap now?
(BTW, why did you say I needed a start cap anyway if it has nothing to do with a fan that can't start on its own?)
p.s.- Are you a HVAC pro working in the Houston area? I may need to call a pro if I run out of things to try.
Hi MrDIY
I am a a/c tech with over 40yrs experience. Houston 204 is right, start caps do not hook up to the condenser fan motor. Let me run this down for you, so you know what is what when your looking at it. Start caps are round and black with a plastic housing and are marked with a range ex.(147-187mf) or higher. Run caps can be round or oval with a all metal housing and have a specific value marked on them ex.(5mf 370volt or 25mf 440v). Run cap values rarely go over a value of 100mf. Their are combination run caps that have 3 terminals on them 1. common 2. fan 3. compressor, which eliminates the need for two separate run caps (one for compressor, one for condenser fan motor. The cap for the condenser fan motor will be in the range of 2.5 to 10 or maybe 15mf. You will just have to look at the value and get an exact replacement. Also the cap with the resistor across it, (assume it is the start cap for the compressor, don't know for sure without a proper description or stated value) the resistor is to allow the charge voltage in the cap to bleed off over time, and will not effect the operation of the a/c. However if it turns out this cap is a compressor run cap the resistor is a must. The resistor allows a small trickle current to flow through the compressor windings, during the off cycle, to keep them warm so liquid refrigerant will not build up in the compressor crankcase. If liquid does build up there, and the compressor starts, Well...........lets just say compressor don't pump liquid very well, by by compressor. This is very important in the winter of course or any long period of down time to have this small current flowing. So if it is a compressor run cap, put it back like it was, or install a resistor on the new one. Note: This is why owners manuals say, if power to condensing unit has been off for an extended period of time, do not start a/c for 24hrs after power has been restored.
What should you do now, glad you asked. Identify the condenser fan motor cap and replace it. If the new cap doesn't work, replace the motor with a new properly sized run cap. Do not assume that the new motor uses the same size run cap. Note: If the new cap does work, be cautious, the motor may still fell after a week or so, either because of the electrical stress it as been under, or the motor was already bad and it took out the cap in the first place.
PS. Run caps do provide for some start torque to the motor, and will not start without one. But their main purpose is during the run cycle of the motor to bring the voltage and current of the motor back in phase, there by reducing power factor and motor amps.
Let me know how it goes
Doug
Hey MrDIY...
Have you resolved your issue? If you dont mind me asking what did it be? Where did you go out and buy the relay at? I am trying to find places that sell HVAC supplies and i am having a hard time doing so. thanks for any help
Kdr246
No expert..I'll state that right up front...and no offence to anyone....but I think there may be a terminology problem. And it may also depend on location and age of the unit.
If the cap was hooked to the fan..then of course it would be a logical assumption that it was the problem based on the stick test. It would be the cheapest fix and 90% of the time is the problem.
When I had a problem back at my last house it WAS the cap..but it was a combo cap as has been stated. I wound up buying a universal and with the right jumpers it worked fine. There were no resistors or anything..those were possibly in the unit itself? A slightly bad motor may function with a brand new cap..but will stress the cap as was stated. Only experience will tell you if a fan spins enough w/o power when spun with a stick. Bad bearings/bushings..built up junk in the housing...plenty of stuff will tell you if there is something amiss when you've seen 100 of the same thing.
Of course if it wasn't hooked to the fan somehow there would be no need to replace it.
dddpope..I respect your stated HVAC experience...but in 25 yrs of electronics..I never heard of bringing current back in phase.....huh?
The start cap serves the compressor, but if it is leaking it may not be a bad idea to replace it.
The start cap is is only serving the compressor for starting, (2 to Herm) after which it is taken out of the circuit by the start relay.
As Doug has stated, the run cap, in this case a dual capacitor, serves the fan motor.
NATE certified tech, serving the Houston area since 1991, at your service
To kdr246: Yes, I fixed my parents' A/C fan problem and will post about it later, but to your point about where I got my parts.
I'm sure there are many A/C supply houses around the Houston area, but my parents' house is on the west side, west of Bellaire and the Beltway.
I got my parts at United A/C Supply, 9920 Westpark, 77063 (713-952-5191) because the appliance parts supply house I usually buy repair parts from to fix washers, stoves, etc. referred me there since they didn't have the capacitor I needed and United A/C was just down the street.
I took the old capacitor(s) into United with me and they just matched them up with substitute replacements.
I was the only walk-in consumer customer in the store since they really cater to the independent pro HVAC trade, but I had no problem getting served or getting the part(s) I needed. I guess my money/credit card is as good as anybody else's.
Don't know if I got a fair price since the counter guys just write up all the invoices by hand, but if I can get out of there with a capacitor for $30 and fix my problem, that's fair enough for me.
So...was it the oval shaped cap in the drawing? (Which, because its wired to the fan..most non-pros refer to as the fan start cap..thats what I alluded to earlier). Or was it the relay?
I'm not clear on what the fix was.....
Got the problem fixed (I think...more on that later)!
First off, thanks a lot to Houston204 and dddpope for all their great advice. (Didn't see your post, dddpope, until I had already fixed the problem, but something you said raised another question in my mind...see bottom of this reply)
Anyway, the sequence of events yesterday:
1. Having read Houston204's original reply, and reviewing the circuit diagram, I was convinced it was the Run capacitor so first thing yesterday morning I pulled it from the A/C unit and took it to the A/C supply house to get a replacement.
2. When I got back and was about to install the new Run capacitor, lo and behold, I noticed that the 1/8 inch thick stiff solid copper ground wire that is attached to the electronics control box was broken! Somehow over time, it had shifted to actually be touching the copper refrigerant tubing in the unit and apparently shorted out and eventually broke. (There were some black marks on the refrigerant tubing where the ground wire had been touching it, but the tubing still seemed to my untrained eyes to still be serviceable and not leaking.) Here's a photo of the broken ground wire:
http://i764.photobucket.com/albums/x...m/PICT2753.jpg
3. After this discovery, I started to wonder if THIS was actually the true source of the fan problems - the copper ground wire had finally broken and caused the fan not to start. Maybe it was as simple as this; but since I had already installed a new Start capacitor Saturday and had a new Run capacitor in hand, and Electrical parts are final sale - no returns was the policy at the A/C store, I decided to go ahead and just install the new Run capacitor anyway. Not having my soldering iron with me, I made a quick trip out to a nearby Home Depot to buy a small wire clamp to fix the ground wire and then pulled the wire bundle away from the refrigerant tubing using a long plastic cable tie to avoid another shorting problem in the future.
4. I installed the new Run capacitor, reset the nearby electrical disconnect, and the faraway circuit breaker and had someone inside the house turn on the thermostat to Cool while I stood outside and watched the start-up. And, YES!! The fan motor started up right away!
5. I then had the thermostat turned back off after a few minutes, disconnected the nearby electrical disconnect, and turned off the breaker. Since I had a big sheet metal panel removed from the outside A/C unit, I took some time to clean the condenser coil fins with some foaming cleaner I bought at the A/C supply store.
So, it seems to be all's well that ends well. HOWEVER, I am curious about a few things now that maybe the HVAC pros can chime in on to satisfy my curiosity:
A) Did I install a new Start and a new Run capacitor unnecessarily? Could the problem fix have been as simple as a broken ground wire to the electronics box? I didn't do a full elimination test by putting all the old capacitors back in with just the repaired ground wire since I figured I couldn't return the caps. My guess is that a repaired ground wire was not enough because the compresser would still run with that broken ground. Also, I did the poor man's capacitance diagnostic test on the old Run cap's Fan terminal using the Ohms setting on my digital multi-meter and found that the Fan and Common terminals together would not show the cap charging up (no increase of ohms at all).
B) As of yesterday, I happily concluded that the A/C was completely fixed until I read dddpope's post today. My old Start cap had the external resistor bridging the contacts and my New replacement one does not. Otherwise, all of the electrical specs on the old and new Start caps are identical. However, now dddpope's post about the resistor being needed to allow a small current to trickle to the compressor to avoid it blowing up (I suppose in the worst scenario) has got me worried. Is the resistor really necessary (could the new cap have it internally?) and do I need to solder one onto the new cap myself, or just put the old Start cap back in the unit? (The old Start cap might actually not be an option because it also failed the multi-meter diagnostic test; in fact the bridging resistor is probably bad too since it shows infinite resistance.)
So...was it the oval shaped cap in the drawing? (Which, because its wired to the fan..most non-pros refer to as the fan start cap..thats what I alluded to earlier). Or was it the relay?
I'm not clear on what the fix was.....
It was the Run cap (or what I've also seen referred to as the Dual cap since it is connected to both the fan and the compressor. It happens to be a cylindrical cap in my parents' Rheem unit although it is represented in Houston204's schematic as oval.
BTW, I think you hit one of the problems squarely on the head GunGuy45 - Most non-pros refer to [the Run cap] as the fan start cap. That's what got me headed down the wrong path initially since I knew there was a Start cap in the system. I just didn't realize that that Start cap was only for the compressor until Houston204 explained it in his original reply.
Great information and help all around on this forum! Thanks.
I'm a general building contractor here in Lodi,CA. We are now hitting 106 F for the 4th consecutive day with increasing heat to 111 f predicted for 4 more days. My neighbor ,a nice retired teacher,recently broke her leg,and is now losing her house in forclosure.To top it off , her AC went out at the start of this heat wave. I voluteered to be a good samaritan and fix her AC,but I never could have done it without your help. You are a hero 'dddpope' and also the moderators who also assisted. Thank-you so much for your valuable input. You are inspiring me to try to give others a hand as well. Great Work Guys !!
Tags: condenser, starts, stick, push, start, capacitor, wasn, ground wire, condenser motor, photobucket albums, with stick, broken ground, Houston area, http s764
