HVAC condensor fan outside intermittant

[pipsters]

Question -

I've got 2 units and noticed tonight, while the downstairs unit cycled on, the air was warm. And got warmer. Didn't get cold quickly. Ran outside and saw the blower/fan motor on top was not turning.

Quickly ran inside, turned the unit off with the T-stat. Went outside, spun the motor by hand, it is smooth. No roughness or binding.

Go inside, flip the unit on with the T-stat, motor outside turns on and runs fine. Inside temps coming out of the duct are around 45F, inside temps around 75F and outside around 70F. Same for the upstairs unit, so the downstairs unit seems to be OK even after running with no blower for 3 mins or so.

I'm new to electrical. Don't know anything save for doing basic wiring and even then I have to follow books step by step.

From research I've done it is either the motor itself, which I've found online for around $120 from Grainger, or possibly a capacitor. Not knowing anything about capacitors, how would I test it? And would it make the motor run intermittently? If I replace the blower fan motor, does the new blower fan come with the new capacitors required? Or should/must I buy new ones as well?

Here is my blower motor, part # GE 5KCP39BGS162S, I believe this is a drop in replacement for it.

http://www.grainger.com/Grainger/GENTEQ-Condenser-Fan-Motor-6DLL8

I want to fix whatever the issue is, money is no issue at this point, because if the unit overheats we are screwed, it will damage the a/c unit. I'm OK replacing the motor and capacitors just need to know what to buy.

 

[pipsters]

OK doing some more reading. It's a split capacitor motor which I believe, from further reading, means only one capacitor.

Now, would this capacitor allow it to start intermittently or should I replace the motor and capacitor?

 

[pop pop]

Slow down a bit. The unit will have some other protection. Intermittent problems are hard to find. I'd first look at the contacts on the contactor. Maybe they've served their useful life. If not, is the capacitor for the fan motor only or combined with the compressor. Is it start/or run? They can be checked, but replacement by same rating isn't expensive. Motor failures, unless a bearing, are usually llike a light bulb. Either it works or it wont.

 

[Basskiller]

Yup, check the contactor. Put your probes accross the 2 sides and see if you have a voltage drop. Visually see if the contactor is discolored. If you have a bad capacitor they usually look swollen. Turn off power to the unit, Discharge the cap, remove wires. check the labeled micofared and measure to see if in spec. When i run across a bad cap, always check the resistance of the motor. Sometimes the bad cap will make the motor go south.

 

[Socophreak]

you can also quickly check using ohms or continuity check to check the terminals and either terminal to the capacitor case. Any continuity and the cap is shot.

 

[pipsters]

OK guys back home after being gone a few days (had to leave the next morning). Here is a pic of the outside cap.

Looks to me like that is the problem - the connector on the cap/wire is completely rusted. The other cap is slightly rusted but nothing nearly as bad.

As far as testing things - keep in mind I'm a complete electrical novice outside of putting leads on a 120v outlet and reading...120 volts.

I'm thinking of cleaning the contact or just replacing the cap.

 

[pipsters]

OK I cleaned the contacts on the capacitor. Unit has run fine for the last few days. Fan cut out again tonight.

Just wondering where I need to go from here. I'm also going to call in a pro for the service check to see if he can troubleshoot as well, just wondering if I can look at anything in the mean time. Luckily we have two units, so one can operate for now, so I have a few days and don't need to call someone in on the weekend.

 

[pipsters]

Old capacitor tests 30/5. The compressor side is out of spec but the fan side is within spec. So I don't believe it to be the capacitor in this case (needs to be replaced anyway due to compressor side being out of spec).

New cap tests 36/5 so I know my meter is working. Wondering what to do next - how do I test the fan motor?

 

[theoldwizard1]

Same Problem. Bearing "stiction".

First time I turn the A/C on each season, I go outside and use a stick to "flick" the fan.

Once per season and I'm good for the past 4-5 seasons !

 

[pipsters]

Same Problem. Bearing "stiction".

First time I turn the A/C on each season, I go outside and use a stick to "flick" the fan.

Once per season and I'm good for the past 4-5 seasons !

The problem I have is that sometimes it will start, and sometimes it won't. The two times I have noticed it, it had run in the evening and late around midnight it did not come on, but the compressor was humming away.

 

[pipsters]

OK the unit is back to doing it again. Called another tech. Could not figure it out. Tired of dealing with companies and spending money not getting anywhere and a/c is not getting fixed!!

Took the cover off the unit. Keep in mind I have two units exactly the same.

New motor is fine. Old motor is fine. No bad bearings. Ohms check OK.

Circuit board inside panel on unit messing up has a HOT resistor. 150*F. Marked 330 ohms. With tstat wire bundle plugged in but not powered (off at breaker) it checks bad. With the tstat wiring bundle unplugged it checks at 325 ohms. There is no power going thru the bundle either way.

Opened other unit. With power off but tstat wiring bundle plugged in same resistor checks out at 343 ohms. Marked 330 +/- 10%. Let both units run. Upstairs unit (working fan) the resistor on the circuit board stays cool, 70*F. On intermittent unit the resistor gets hot quickly just by flipping the breaker to the tstat thereby powering the unit.

Thinking a bad board or possible defrost sensor. Going to swap out the tstat to see if that fixes if, if not thinking about swapping the board out with the other one I have on the other unit to test.

FWIW the first tech said "I've never seen a bad circuit board ever" and dismissed it. Sounds like a bad board to me. I knew something was up, that motor was fine. The unit is a Carrier heat pump.

 

[lzenglish]

Check the thermostat and wiring for shorts, or loose conections, and proper voltage. Check the mag starter for dirty points, shorts, or loose connections, and proper voltage to the coil (24 volts AC). If both are good, swap out the boards, and see if the problem follows the board to the other unit. Be careful to have yourself well grounded, when handleing the boards, as static electricity can take them out, and be sure to mark the suspected bad board, so you don't loose track of it. FYI: I use "Freeze Mist" Spray, when I think my problem could be a Board Solid State Componet, such as SCR, Resistor, or Transistor is overheating, and causing problems. I spray individual componets one at a time, such as your hot resistor, and see if there is a change in the unit operation, when it is in the fail to run mode. Remember, you run the risk of taking out the spare unit board, if you have a shorted componet in the Heat Pump. Then you will be in a world of shite! Good Luck!

Wayne

 

[Jagmandave]

Are the outside units clean, all the fins clean and so on?

If the head pressure gets too high it will shut off compressor, but on my unit the whole unit shuts down, inside fan and all....

I think you found your problem, I think you have a bad board.

 

[pop pop]

Same Problem. Bearing "stiction".

First time I turn the A/C on each season, I go outside and use a stick to "flick" the fan.

Once per season and I'm good for the past 4-5 seasons !

Unless you want to replace the motor, I suggest you remove and clean and resaturate the oiled wicks in the bearings in that motor. Sounds underlubricated and once the metal is gone, it won't fix.

 

[pop pop]

Contact Carrier direct. There isn't anything they haven't seen with their units.

 

[pipsters]

Contact Carrier direct. There isn't anything they haven't seen with their units.

They just referred me to the authorized dealer

Wish they had the service manuals online

 

[pipsters]

Check the thermostat and wiring for shorts, or loose conections, and proper voltage. Check the mag starter for dirty points, shorts, or loose connections, and proper voltage to the coil (24 volts AC). If both are good, swap out the boards, and see if the problem follows the board to the other unit. Be careful to have yourself well grounded, when handleing the boards, as static electricity can take them out, and be sure to mark the suspected bad board, so you don't loose track of it. FYI: I use "Freeze Mist" Spray, when I think my problem could be a Board Solid State Componet, such as SCR, Resistor, or Transistor is overheating, and causing problems. I spray individual componets one at a time, such as your hot resistor, and see if there is a change in the unit operation, when it is in the fail to run mode. Remember, you run the risk of taking out the spare unit board, if you have a shorted componet in the Heat Pump. Then you will be in a world of shite! Good Luck!

Wayne

Thanks for the writeup and tip about static electricity, I had forgotten about that, fortunately I got lucky. I ended up solving it yesterday mid-day after getting back home the night before. It was a bad defrost sensor.

I swapped boards from my other unit and still the same resistor got hot. Put the boards back where they originally were.

I unplugged everything to the board, then plugged in the tstat wiring harness and flipped the breaker. Then plugged in component by component. The last thing to go in was the defrost sensor. Resistor started heating up. Ohmed the defrost sensor got around 150 ohms @ 80*F. Should be in the 8000-10000 range, although I can't find any Carrier specific charts. Plugged the bad defrost sensor into the other board, bam resistor started getting hot. $23 repair.

The best part is I can now, with confidence, use my a/c without worry. I unplugged the defrost sensor and am running it until the new one gets here, it's hot so the coils won't freeze up.

The last two weeks have been a crash course in HVAC .

 

[hobie1dog]

great troubleshooting...congrats

 

[lzenglish]

I agree with "hobie1dog"!!! You did a fantastic job of troubleshooting, congrats to you!!!!

The great thing about this experience, is that you saved a bundle of money, and you are now very familiar with your two units! If I was still working, I would hire you in a pair of seconds!

Take Care,

Wayne

 

[pipsters]

Thanks guys a month ago I didn't even know how to use a multi-meter, slowly getting better but electricity is like Greek to me. Feels really good to fix this thing finally.