Need roof air conditioner capacitors - fan motor doesn't always run

[cubano222]

I can't seem to find anyone to help me in the Nashville area on my a/c capacitors. Campers World want to know the model # of my roof a/c but I've taken the top shroud off & got the 3 capacitors out & I took the inside cover off. The only thing I've found is Duo Therm standard line 546 & 54808 series. No one seems to be able to match the original capacitors.
The large rectangular one has 78-39  598  21L3130  30.uf    dielektrol
The smaller rectangular one has 78-44  122  21L3010  10.uf    dielektrol
The small round black one has 61-72MFD  250vac  3-5046-011    235-7843-04  Mallory
I hope someone here can help me. I wanted to replace all three but the only problem I have is sometimes the fan motor just hums & sometimes it comes on.
Thank you,
Jerry

[pvoth1111]

try Grainger or a HVAC supply house

[mrmuse]

Like these?

[mrmuse]

All 3 on Ebay for< $23.00
   
30 MFD - 370 VAC ROUND RUN CAPACITOR PRC30
Run Capacitors Round 370Volts 7.5MFD, 10MFD, 25 MFD
Tecumseh Capacitor 85PS250C19 88-108 MFD 250 VAC

mrmuse

[cubano222]

Exactly like those. Will try ebay but may run to Graingers in Nashville to see what they have.
Thank you all so much for your help.

[mrmuse]

Keep us posted.  I added an inline hard start cap @ replacement time..

http://www.ebay.com/itm/SPP6-SUPCO-POW-R-PAK-Starter-Solid-State-Relay-And-Hard-Start-Capacitor-/161137981489?pt=LH_DefaultDomain_0&hash=item2584927831

mrmuse

[cubano222]

Does this capacitor replace my round black one?
Is this the place you got all 3 capacitors? I just want to make sure they match the original ones.
Thank you so much for your help.
Jerry

[mrmuse]

Here are current links:

http://www.ebay.com/itm/30-MFD-370-VAC-ROUND-RUN-CAPACITOR-PRC30-PACKARD-NEW-/151075602528?pt=LH_DefaultDomain_0&hash=item232ccec060

http://www.ebay.com/itm/PRC7-5-Round-7-5-mfd-uf-370-Volts-Motor-Run-Capacitor-/380738532035?pt=LH_DefaultDomain_0&hash=item58a5c8f2c3

http://www.ebay.com/itm/Mars-11045-Motor-Starting-Capacitor-88-108-MFD-250-220-VAC-New-/321227214609?pt=LH_DefaultDomain_0&hash=item4acaa24f11

mrmuse

[cubano222]

So these 3 will replace the 2 rectangular & 1 round capacitors I have? Do they plug in just like my old ones? I'm sorry but I'm dumb when it comes to these. I just want my roof a/c to work right.
Thank you so much.

[HandyDan]

Maybe this will help.  When it comes to high voltage electricity, it scares me, however, I recently replaced my capacitors and nothing blew up.

Edit:  Just noticed that this does not include the hard start capacitor.  (The round black capacitor)  It is wired in parallel with the run capacitor to add an extra boost at start up time. 

[cubano222]

Thank you for the diagram. That helps me a lot. I just didn't know if the 3 links mrmuse sent me with a round run cap, a round motor run cap, & a motor starting cap will be the same as my large silver rectangular cap, the smaller silver rectangular cap & the small round black one & if the pins were the same on these replacements.

[cubano222]

On the pic you posted, which one from ebay replaces the large silver rectangular one, the smaller silver one, & the round black one. I know how my old ones were wired but I don't know which of the ones from ebay replaces the old ones.

[mrmuse]

My new one were not physically identical, but as long as the values match you should be fine.  I ended up stacking one on top of the other and I used a small piece of rubber mat for insulation between the 2 so  no shorts.

mrmuse

[doylexl]

Hard start kits are for the compressors not the fan. My roof ac fan would not run unless You helped it by pusuing it with Youur hand after replacing the relays and capacitors it still would only run if you helped it with your hand . I replaced the fan motor and now it works great.

[ductman]

As long as your compressor is starting fine there is no need to replace those capacitors. Capacitors either work or not I would replace 10 mfd for fan mtr and see if fan motor turn on its own if not the fan mtr is bad. I am a Hv tech for 33yr I see this all the time!

[cubano222]

I'm getting more confused. Which one is the fan motor run capacitor? The round one, the small rectangular one or the large rectangular one. None of the original ones say 10MFD. My small round one says 61-72 MFD

[mrmuse]

1.  What model A/C unit?
2.  Photos if possible??

If you don't have a manual, there should be a diagram inside the unit itself.

All I can do is relate what I did for mine, so the more info you provide to us, the better.

mrmuse

[cubano222]

I couldn't find a model or diagram anywhere on the unit. All I found was a label that says Duo Therm Standard Line 546 & 54808 series.
My capacitors look exactly like the pic you posted but I don't know which one is the motor run capacitor. The compressor comes on even when the fan doesn't but if the compressor stays on too long without the fan running, it shuts off. So I'm thinking I just need the capacitor that will start the fan motor. Sometimes the fan motor will start right up & run for a while but then shuts off & just hums.

[cubano222]

After digging around, I found a HVAC parts store 3 miles from my work. Didn't know they were there. He was nice enough to test all my capacitors & showed me the compressor cap & the start cap checked out perfect. He even showed me the readings on new ones compared to mine & the readings were the same. The black round run cap tested faulty. He didn't have one in stock but ordered one & will have it in by Friday. I hope to get my a/c working this Saturday

[mrmuse]

Great..

mrmuse

[ductman]

My apology I read your post wrong I thought it said 10 mfd but you posted 10 uf! That faulty capacitor should fix the problem like I had said before capacitors are either good or bad no in between.

[cubano222]

Thank you all for all the great replies & help. It's awesome to have resources like this to get help on stuff you don't know anything about. I've been in the Home Medical Equipment business for 36 years & at my present job for 23 years. I have a lot of knowledge on oxygen, cpap, wheelchairs, hospital beds, ect. When it comes to electrical stuff, I'm lost. In the 5 years I've had my 1979 RV, I've learned so much from great people like in this site. I know I'll be coming back with more questions cause something always comes up. Thank you very much.
Jerry

[Oz]

Do let us know if you get the A/C running right.  It's a good feeling when I get to put the green checkmark on the first post.... "solved"!

[cubano222]

Well, bummer. Went out today & turned on the a/c & the fan motor just hums like it did before. The compressor comes on but the fan motor does not. If I go on the roof & spin the fan, it comes on. I put in that new capacitor so I guess my fan motor is bad. There are no oiling points on the motor itself & looks like I will have to take off a lot of metal around it plus a bunch of styrafoam insulation to get to the motor mounts.Any body have instructions on how to remove the motor?

Crazy that if I put a little spin on the fan & turn the a/c on, the fan motor comes on. The new capacitor I bought is a Start capacitor 72-88uf 250/220V which is suppose to replace the stock one.I don't know if I need a stronger capacitor to get the fan motor started or my fan motor is shot. If the fan motor has to be replaced, I have no idea how to remove it. It looks like a tough job.