Outdoor HVAC fan trouble

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  #1  
Old 08-10-10, 09:53 PM
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Outdoor HVAC fan trouble

It's Murphy's law. It's so hot out here and lo & behold...

I have a Carrier WeatherMaker (with heat pump) that is 11 years old that stopped blowing cool air. Some observations:

1) Outdoor fan does not run.

2) Compressor motor runs and I can feel the pipes cool. But the compressor shuts off in 3-5 minutes. I guess that's some thermal protection kicking in due to the dead fan. Contactor "de-contacts" during this shutoff.

3) Traced wires from motor head. Brown & Black go to capacitor. Black goes into a black box on the control board - Fan relay?

4) There is no voltage at this fan relay pin where the black wire gets plugged in, when the compressor is running or otherwise!

The control box looks like this:
Carrier Bryant Defrost Control Board CESO11006302
The back box on the top left is where the fan's black wire plugs into. (Another black wire runs from the other pin on this black box to the vapor pressure switch)

Here's the wiring diagram (1st page)
http://www.docs.hvacpartners.com/idc...t/38yxa-3w.pdf

Is the fan is getting power? Here's my question:
Can I unconnect the motor wire from the relay (if that is the relay) and connect it directly to the load side of the contactor, only momentarily, to ensure that the motor gets the power?

Your input is appreciated. Thanks!
Alex

ps. I suspect that the fan stopped working towards the end of winter itself because I noticed the Aux Heat sign on on the tstat. That explains the high heating bills
 

Last edited by AlexWoods; 08-10-10 at 09:57 PM. Reason: Missed out a couple of important observations
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Old 08-10-10, 10:30 PM
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First make sure the power is off to the unit. Remove the two wires from the black box (fan relay) and connect them together with a short piece of wire (preferably with two male spade connectors on each end). Turn on the system and set to cool. If the fan runs replace the defrost board in the picture. If it doesn't run replace the capacitor. If it still doesn't run replace the fan motor.
 
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Old 08-10-10, 10:39 PM
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Hey jeggs, Thanks!
I didn't expect a reply this late.
I am itching to try out your suggestion, but it's 1.30 AM, so I will do it first thing tomorrow. 2 questions:

1) If connecting the 2 wires from the fan relay gets the motor running, can I let it run for an hour, while I go out and get a new board?

2) Can I not just replace the relay?
 
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Old 08-10-10, 10:54 PM
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You could leave it like that till you get the new part and use your A/C if the fan runs. Tape the wires up good so they don't short out on anything. If the relay unplugs from the board you could probably replace it but most of them are soldered onto the board.
 
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Old 08-11-10, 09:37 AM
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Unplugged the 2 black wires that plug into the fan relay. (1 goes to motor, the other to a vapor pressure switch on the compressor line that is cold)

Connected the same 2 black wires to each other using a male-male spade connector.

Set to cool & reactivated outdoor disconnect.

Still no fan! Compressor runs fine.

There is still no 220 V at the spade connection junction, meaning that no power to motor.

This means that there is no power coming from the vapor switch, which I confirmed with a voltmeter.

Went on to connect the fan's black wire directly to the contactor's load side. Now the fan works! I hope we have narrowed this problem down a bit.

1) With the jumped fan wire, can I cool the house on an as needed basis?
2) What should I do next about this vapor pressure switch, or anything else?
 
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Old 08-11-10, 11:18 AM
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Bypass the vapor pressure switch and your A/C should run fine. The vapor pressure switch is for heat pump operation in the winter and explains why the heat pump wasn't working in the winter and the aux heat indicator was on. Replace the vapor pressure switch before cold weather comes and make sure the heat pump is working correctly in heat mode (aux indicator off).
 
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Old 08-11-10, 12:05 PM
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Bypassed the vapor pressure switch. AC runs like a charm now. Wife has stopped complaining (about the AC).

Now, the vapor pressure switch is mounted on the thinner of the 2 cold lines.
1) Is is possible to simply pull off that switch for replacement?

2) Would the refrigerant line be opened up to atmosphere when I remove the switch?

3) Is the switch screwed in? I can't tell. It all seems to be one piece, copper tubing, switch and all.
 
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Old 08-11-10, 12:10 PM
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It should unscrew for replacement. There should be a schrader valve in the port it is on to prevent refrigerant from escaping when it's removed. Can you post a picture of it. Don't force it out as it may damage the tubing.
 
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Old 08-11-10, 12:59 PM
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Very well, jeggs. I will post a picture of the valve as soon as I get my camera. I should have it tomorrow night. Thanks for all the advice and info.
 
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Old 01-10-13, 05:56 AM
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Vapor Pressure Switch

How did this end up? My OFM stopped working, unit iced up. I bypassed the VPS and it works fine now. What does the VPS do? Did you have to recover and recharge the system to replace the VPS? Thanks!
 
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Old 01-17-13, 09:05 AM
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hvac fan issue

Dear all,
For the last few days i am facing an issue that condenser fan is not running smooth and making a sound while attempting to run(fan taking jerks) using utility power but the same HVAC when run through generator fan are running smooth. I have checked all the voltages up to transformer end and found ok, kindly if any one can guide me how to solve this issue
 
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