Fan or Cap


  #1  
Old 05-07-07, 12:38 PM
L
Member
Thread Starter
Join Date: May 2007
Location: TEXAS
Posts: 26
Received 0 Votes on 0 Posts
Fan or Cap

When I returned home saturday I walked into a 90+ house. The inside air handler was running and the vents were blowing just cool air. After going outside I found the compressor was running but not the fan. I have read some of the other post but could not get anything in the grill to spin the fan. We always sit on the patio in the evenings and have not noticed any abnormal noises from the unit. I disconected the power, discharged the fan cap and removed. The fan spins very freely. I do not have any opens on any of the three wires from the fan. I also checked all three wire to groung, all were open. Now my question, The cap only has two sets of lugs on top. does it matter which one I put the wires on? Two of the three wires (purple and tan) plug on to the top of the cap. I have one smaller guage wire that connects to the cap from the contactor that goes on the same side as the purple wire. The third wire (black) goes to the contactor. Any help would be great as I have bought the new cap and hope to get this running tonight. Thanks in advance for your help.
 
  #2  
Old 05-07-07, 02:24 PM
H
Member
Join Date: Mar 2007
Posts: 76
Received 0 Votes on 0 Posts
It doesn't matter which terminals you use on the new capacitor for which group of wires; just be sure to wire the new one exactly like the old one as far as which wires go together on each terminal. There was a time when small motor run capacitors had an identified terminal which was supposed to be connected to the power coming to the capacitor [in this case the purple wire] but today's caps are no longer made that way. Also, the new capacitor has to be the same microfarad rating as the old one. This is the mfd or uf number on the capacitor [mfd and uf mean the same thing, some caps are labeled mfd, some uf]. The vac number is the voltage rating which has to equal to or greater than the old one. In air conditioning units there are only two different vac run capacitors; 370vac and 440vac. You can replace a 370 with a 370 or a 440 but you can't replace a 440 with a 370, only another 440. To recap, the microfarad rating wants to be the same as the old one and the vac rating can be equal to or greater but never less than the old one.
 
  #3  
Old 05-07-07, 02:38 PM
L
Member
Thread Starter
Join Date: May 2007
Location: TEXAS
Posts: 26
Received 0 Votes on 0 Posts
Thanks for the ifo. The old cap was labeled 7.5uf. It read when checked 5.41uf. I bought the new 7.5uf and it reads 7.49uf when checked. I thought the contactor but it looked clean and the compressor runs great. I hope this is the fix. The old cap was in a sealed plastic case and did not look bad but when I tested it it was about 2.3uf under want was called for on the fan motor. Thanks again for the help.
 
  #4  
Old 05-08-07, 12:01 PM
L
Member
Thread Starter
Join Date: May 2007
Location: TEXAS
Posts: 26
Received 0 Votes on 0 Posts
Update

Well the cap went in with no problem. Closed unit up. Called for cooling. Compressor runs fan still inop. Retested fan motor leads and all had resistance between leads. No contact to ground. Does anyone have any other suggestions before I do the fan motor? The system seems very straight forward. Three leads from motor. Purple to cap ( with red small guage wire from contactor) Tan to cap and Black to other side of contactor. I would think if the compressor is running then the contactor is doing the jog. Any help is needed.
 
  #5  
Old 05-08-07, 12:53 PM
H
Member
Join Date: Mar 2007
Posts: 76
Received 0 Votes on 0 Posts
Every once in a while you'll run across a nicked wire going to the motor. Check for voltage from the black wire to the red/purple terminal at the capacitor to see if the motor is being supplied with power. If that's ok, try giving the motor a spin while it's energized to see if it will even start. Oftentimes, the bearings or spacer washers inside wear to the point where the rotor isn't properly situated in the motors' magnetic field which will prevents the motor from starting. If you wind up replacing the motor, check the nameplate on the motor to see what size capacitor it uses. It may not be the same as the new cap you bought.
 
  #6  
Old 05-09-07, 07:06 AM
L
Member
Thread Starter
Join Date: May 2007
Location: TEXAS
Posts: 26
Received 0 Votes on 0 Posts
Problem Over

I want to thank everyones help on this. I when to Grainger and purchased a new 1/4 hp 825 RPM ball bearing motor that was an oem for condenser fans. I also purchased the new cap for this motor. Everyone I had talked to had told me to expect to have to do some rewiring as the replacement motors do not have the same wiring or colors. As luck would have it the motor had trhee leads, the same colors as the old one. I followed the post on removing the fan from the old one and the job was complete in about 45 min. I had set aside 3 hours. Cleaned the compressor and coils and still had time to spare. All is back to normal at a fraction of the cost. This is a great site and will recomend it to all that ask if I know about a/c. Thanks
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: