replacing 3 wire to 4 wire compressor fan - please advise!

frazwr01

Hi all,

My compressor fan in a 21 year old Carrier (model 38TK024300) started turning very slowly last night (probably about 100 RPM or so). So my first thought, after reading some forum posts, was to replace the capacitor. I did this, but I had to replace the old dual capacitor with two "single" ones. The uF and voltage ratings for the compressor and fan sides are the same as the original, so no worries there.

OK, so this did not solve the problem (fan is still turning slowly and compressor doesn't come one [hopefully the compressor is in some sort of "protection mode" rather than just dead!]).

So now i'm replacing the fan. My original fan is a GE model HC35GE230A. The replacement fan I was just sold is an A. O. Smith model (#FE1018SF).

The old fan has a black (hot) wire, a yellow wire connecting to the C terminal of the old dual capacitor and a brown wire which connected to the "fan" terminal of the capacitor. The new fan has 4 wires: black, white, brown, and brown/white. The black and white wires can be reversed (via a small plug) in order to achieve the correct fan direction.

So, I've seen two options for how to wire this thing (and I'm not sure which is best, or if it even matters).

Option 1: connect black wire as before (same as original motor), connect brown to one pole of the fan capacitor, connect brown/white to other pole. Finally, connect white wire to same pole as brown/white.

Option 2: Same as above, but do not connect brown/white.

FYI: the fan and compressor capacitors are bridged by a connecting wire right now -- I was told that this setup is the same as a dual capacitor. So to clarify, brown fan wire goes to one post of fan capacitor, brown/white and/or white motor wire will go to terminal #2 (depending on option 1 or 2 listed above). Terminal #2 has a wire going to a terminal on the second (compressor) capacitor. That terminal of the 2nd capacitor also has a yellow wire going to the compressor. Finally, the second terminal of the compressor capacitor has a thicker blue wire which also feeds into the compressor.

Also, here is a link to the wiring diagram, etc for the new motor:

http://drawings.aosmithmotors.com/se...ngType=OUTLINE

Hopefully I'm on the right track... thanks ahead for anyone's advice!

Marty S.

Use option 1 except hook the white wire to the same side of the contactor that the compressor's capacitor wire hooks to.

frazwr01

Thanks, Marty. I went with option #1, and unfortunately my problem still persists -- fan still rotates very slowly and compressor doesn't seem to kick in. Since my A/C is so old, the electrics are fairly simple. It seems like after replacing the capacitor and the fan motor, the only thing remaining that could be causing this is the contactor malfunctioning.

So I'll disconnect the contactor today and see if it needs cleaning or anything (by the way, the contactor appears to be fairly recent -- no more than 5 years old I would say).

Any other suggestions or troubleshooting tips? Maybe check the voltage coming out of T1 and T2?