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Author Topic: A/C Fan Wiring Question  (Read 323 times)


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A/C Fan Wiring Question
« on: August 13, 2017, 09:01:57 AM »
I've been trying to get my front rooftop A/C working for a while (well, more like thinking about it really hard and not really doing a whole lot...) and I've done all the "normal" stuff and tested a few things and can't seem to come up with a solution.  In the process, though, I found a good deal on a used unit that had a compressor that worked, but the fan is locked up tight.  I basically paid scrap value for it, so I figured it was worth a shot to repair it since, after all, I've got a fan that works on the A/C unit I already have!

In trying to swap the fans, however, I've run into a hiccup on the wiring.  The working fan is a 5-wire fan and the seized one that I pulled out is a 4-wire fan.  The old fan had red and black going to some wire nuts and then the white wire and a brown wire going to the capacitor.  The newer fan shows a diagram of red going to low speed, black to high speed, white to line, and then brown/white and brown to what appear to be a capacitor on the diagram.  The old unit with the 4-wire fan has its white wire connected to the capacitor that the white and brown are connected to.  (see attached diagram)

My guess is that I want to directly connect the unit's white wire to the fan's white wire and then send the brown and brown-white to the capacitor.  Am I on the right track?
1993 Itasca Suncruiser 32RQ / Chevy 7.4

John From Detroit

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Re: A/C Fan Wiring Question
« Reply #1 on: August 13, 2017, 04:39:15 PM »
Without the motor's wire chart, Which is often ON THE MOTOR itself I Can not be sure which With is Which but..

ONE Wire.. Often white.  Will be common. The others are High/Med/low and in between

Figure out which is common. and connect JUST that wire.. also connect a voltmeter black lead to that (120 VOLT Ac) and have your partner set unit to HIGH FAN.  CAREFULLY (DO NOT TOUCH METAL figure out which of the otehr wires is not LIVE.

Now. Test (Turn off, connect to one wire, turn on listen) to find the HIGH wire.. Identify the others while at it.

Now do the same for MED and LOW (When you ID a WRONG wire, label it)

You will tape off the remaining wire Tape it off well (no exposed metal multiple or better yet apply s wire nut and tape it in place)

How we did my fan.
Nothing adds excitement like something that is none of your business
My Home is where I park it.


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Re: A/C Fan Wiring Question
« Reply #2 on: August 13, 2017, 09:49:07 PM »
I believe you are exactly correct, wae (if I read your post correctly.)

Schematically, you should end up with connections as shown in the "Replacement Motor" sketch attached.  Well, I HOPE it's attached
Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."


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Re: A/C Fan Wiring Question
« Reply #3 on: August 15, 2017, 06:28:27 AM »
Thanks for the help! 

I did go out last night and wired things up that way.  Basically matched wire colors and put brown and brown-white to the cap.  The fan now runs at one speed regardless of the position of the control switch.  With everything turned off, the fan starts up as soon as I plug the unit in.  When I put the switch to the "cool" position to engage the compressor, the compressor did kick on but I immediately pulled the plug because I got some sort of short at the run cap.  I'm going to go back to the drawing board on my electrical connections based on the original wiring diagram, but something is not hooked up correctly.
1993 Itasca Suncruiser 32RQ / Chevy 7.4