Need help diagnosing Condenser Fan issue - http://www.hvacmechanic.com/ Forums
Original message
| kushane
 |  "Need help diagnosing Condenser Fan issue"
, posted Wed 4 Jun 21:14  
Hoping someone can help with a frustrating problem I am experiencing. I have a 8-yr old Trane XE1000 unit and the the condenser fan does not always turn on with the compressor. The blower fan turns on and I can also hear the compressor humming outside, but the condensor fan does not turn on initially. After what seems like a random period of time (about 4-8 mins) the fan will start and then a while later stop (while the compressor is still running). This whole issue is very intermittent, but is more frequent later in the day after about 7.00 PM.
I had a reputable local HVAC company come by twice in the last 2 days and the whole time they were here, everything would work just fine. Said the Capasitor is fine, but pointed out to a generic brand condenser fan (as opposed to a Trane fan I guess) and said that it's actually a blower fan installed in the condenser and basically refused to even try to diagnose it anymore.
Is there any diagnosis I can do on this myself? I know my way around a circuit board and how to use a multi-tester etc. I just can't afford to pay $75 a pop to have someone look at it and not find anything.
Any advice is appreciated.
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Replies:
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| theduke03
| "Re(1):Need help diagnosing Condenser Fan issu" , posted Wed 4 Jun 21:29:
Locate where the black and purple fan wires are connected. Check voltage between these terminals when fan is running. Should be 230vac +/- . Then when the fan stops check voltage again. If you still have 230 then problem is with motor or capacitor. If it disappears then the problem most likely be the defrost control(DFC).
Picture displayed here brought to you in part by Houston204.
"My dad was the most feared furnace fighter in Northern Indiana."
[this message was edited by theduke03 on Wed 4 Jun 21:36] |
| | kushane
| "Re(2):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 10:36
Removed the access panels on the outside unit and noticed a few things that were different from the circuit diagram/what you said.
I see a total of 4 wires coming out from where the fan is at:
Brown, Brown/white - both wires going to what looks like the capasitor (1st picture below)
Yellow wire - which is connected to the purple wire which goes in turn goes to the contactor (2nd picture)
Black Wire, which goes to a circuit board with a blinking green LED on it.
Would very much appreciate it if you could provide some additional info on which terminals I should use to check the voltage listed. I am guessing when the condensor fan was replaced previously, they did a very poor hack job on it.
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| | theduke03
| "Re(3):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 18:09
Yes that does look like a hack job. Check for 230v between that purple wire and the black fan wire on DFC. I would also like you to check the low voltage connections for 24v between O and C.
"My dad was the most feared furnace fighter in Northern Indiana."
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| | kushane
| "Re(4):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 19:06
When you said check or 24v between O and C, not sure I know what you are referring to. Are these connections on the DFC board itself?
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| | theduke03
| "Re(5):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 19:20
Oh my bad. I meant O and B(Trane). These are to be checked where the tstat wires connect to unit wires. Diagram above shows O connected to an orange wire, B connected to a blue wire.
You can take off the wirenuts and check for 24v.
"My dad was the most feared furnace fighter in Northern Indiana."
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| | kushane
| "Re(6):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 19:53
I have approx 230V both when the fan is running as we as not running. On the blue and orange wires, I didn't detech any voltage when the fan is running, and I didn't get a chance to check when it is not.
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| | theduke03
| "Re(7):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 20:12
You are checking these voltages between said points and not to ground correct? If so then it sounds like a bad motor or capacitor. You can test the capacitor by doing this:
Shut off power to unit.
Short the terminals on the capacitor with a scewdriver to discharge it.
Remove wires from capacitor.
Set meter to ohms on highest scale.
Put meter leads on both terminals.
If OK then ohms should drop towards 0 then rise towards infinate/open. Then reverse leads and repeat and result should be same.
If ohms are low or high and dont move then capacitor is bad
"My dad was the most feared furnace fighter in Northern Indiana."
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| | kushane
| "Re(8):Need help diagnosing Condenser Fan issu" , posted Thu 5 Jun 21:44:
Correct.. I was testing for voltage with between the Orange and the Blue wires (with one test lead on Blue and the other on Orange).
When I shorted the terminals on the capasitor with a screwdriver, there was no spark or anything which I am guessing should have been if the capasiter was working.
When I put the tester on ohms and put in on each terminal - the needle didn't move one bit. Even lowered the ohms scale and still nothing.
Seems like from what you said, it's pretty conclusive it's a bad capasiter.
2 final questions, looking at the parts list I found, there are 2 capasiters listed:
1) CPT00091 - Capasiter, Start, 330V, Round, W/Resister
2) CPT00669 - Capasiter, Dual, Round, W/O resister
Which one of these do I need, or would either one of them work since I have a generic brand blower fan?
Also, are the number of terminals etc on the replacement parts similar to where I can just remove the old and install the new?
Thanks very much for your meticulous instructions on how to diagnose this issue. Can I email you at the address listed on the profile?
[this message was edited by kushane on Thu 5 Jun 22:00] |
| | theduke03
| "Re(9):Need help diagnosing Condenser Fan issu" , posted Fri 6 Jun 07:16:
Not neccessarily. Your meter may not be appropriate for the cap test, a microfarad tester would be. Also the cap usu. doesn't spark. we just do that for safety. Go ahead and replace it anyway. If that really is a blower motor intended for indoor use then the motor is probably shot too or will be soon. If new cap doesn't help then I suggest calling Trane to get the correct motor for the unit.
For the low voltage wires there should be 24v from O to B. If not then your unit will be running in heat mode.
Which capacitor? The dual(the one you tested and is the only one connected to fan).
"My dad was the most feared furnace fighter in Northern Indiana."
[this message was edited by theduke03 on Fri 6 Jun 07:35] |
| | kushane
| "Re(2):Need help diagnosing Condenser Fan issu" , posted Wed 4 Jun 23:40:
Thanks very much. This was the exact kind of info I am looking for. I'll check the voltage between the those terminals tomorrow and come back with the findings.
Assuming the DFC you mentioned might be suspect.. and that would cause it to go into a 'defrost' mode.. would that result in a different sound coming from both the inside and outside units. I noticed when the fan is not running, there is a noise which I can best describe as a high-pressure releasing / whistling noise being emitted..it's more pronounced on the outside unit.
Any thoughts?
[this message was edited by kushane on Wed 4 Jun 23:41] |
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