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Old 02-19-2014, 02:27 PM   #1
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


Old motor has blk (hi), wh (line) blu (med), red (lo), orange (med lo) wires coming out of Molex connector ( I cut the molex connector wires off at motor, to transfer to new motor). Capacitor wires are two brn wires coming out of old motor and connect direct to capacitor.

New wires on new 3-spd motor are blk (hi), wh (line), blu (med), red (lo), plus brn/white stripe & brn for capacitor.

Molex connector connects to a control box attached to front of blower housiing. Inside this control box is a speed selector switch under molex connection (not familiar with this speed selector switch). There are no Auto/On & Heat/Cool switches on this control box, as I have seen on Coleman Presidential III models that has only a 2-wire connection to T-stat (this Intertherm/Nordyne).

If I hook up the wires from new motor to the wires of matching color on the Molex connector, and cap off the orange (med lo) wire on Molex connector, this should work, yes?

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Old 02-19-2014, 02:46 PM   #2
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


Yes. and make sure you use a marrette and then tape it back over the marrette so it does not fall off later. that wire will have over 100 volts from induced voltage.

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Old 02-19-2014, 02:52 PM   #3
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


Quote:
Originally Posted by yuri View Post
Yes. and make sure you use a marrette and then tape it back over the marrette so it does not fall off later. that wire will have over 100 volts from induced voltage.
Marrette would, no doubt, be a French word for Wire Connector or Wire Cap, or Wire Nut. I do understand and have capped 'em off before. Also understand what induced voltage means. However never thought about or measure that voltage.

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Old 02-19-2014, 03:04 PM   #4
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


Or... maybe it's not a French word at all, but just a brand name of wire connectors...
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Old 02-20-2014, 06:41 AM   #5
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


The old motor would try to run after a couple minutes of flame in heat exchanger, but only groaned. Old motor test bad on my bench.

New motor tested good on my bench, but would not run when I connected all the wires of matching colors from Molex connector & wires (cut off of old motor) to new motor (all speed designations were the same for each color), except for no orange ( med-lo) was on new motor - I capped off.

When it should have run, the only place I found 120v on the speed selector was the bottom-right corner of speed selector. Is it possible this old blower was runing on med-lo? 14' x 70' mobile home, Nordyne model # MGHA-056ABFC-02 Serial # MGH 9507-04716
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Wiring new 3-speed motor to old 4 speed motor molex connector wires-400-_ringling_scan_1700x2192.jpg  

Last edited by justplumducky; 02-20-2014 at 06:56 AM.
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Old 02-20-2014, 09:10 AM   #6
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


If you have power at the blue terminal follow the power up to you molex output to motor. Leave your neutral meter reference point at same location. If you have power to line to motor , now move your neutral reference point to output of molex to make sure you have a good neutral path.
Eyeball your connector pins as well, as they have a tendency to push out and not make a good connection if the barbs that hold them in place are not engaged in the molex properly.
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Good luck and be careful on testing around molex plug, Joe
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Old 02-20-2014, 09:58 AM   #7
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


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If you have power at the blue terminal follow the power up to you molex output to motor. Leave your neutral meter reference point at same location. If you have power to line to motor , now move your neutral reference point to output of molex to make sure you have a good neutral path.
Eyeball your connector pins as well, as they have a tendency to push out and not make a good connection if the barbs that hold them in place are not engaged in the molex properly.
-
Good luck and be careful on testing around molex plug, Joe
Thx for your reply Focused. I can check the pin connections on the molex no problem, but I'm not following you exactly on how to check for good neutral path, but in general, sounds like you're saying I should have power from the blue terminal on speed selector up thru molex to motor which would run motor an med speed. Neutral path then is on white wire from motor thru molex, down to top-rt connection on speed selector, correct?

When there's a call for heat, could you trace the origin of power on my diagram thru the components, to what ever motor speed color wire (blue?) I should set this blower up on?

Last edited by justplumducky; 02-20-2014 at 10:12 AM.
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Old 02-20-2014, 10:41 AM   #8
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


How do you change motor speeds? By choosing whatever wire/speed you want (blk, blu or red) and moving it to the blu terminal on the speed slector?

The two bottom terminals of the speed selector(very bottom left , and bottom right)- are they both supposed to be hot?

Last edited by justplumducky; 02-20-2014 at 10:45 AM.
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Old 02-20-2014, 11:24 AM   #9
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


did you put a brand new capacitor on the motor and is it the correct size? check it with your meter for mfds if you have one.
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Old 02-20-2014, 12:05 PM   #10
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


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did you put a brand new capacitor on the motor and is it the correct size? check it with your meter for mfds if you have one.
Brand new, correct size for the motor, but didn't check it yet Have meter w/capacitance - have to pull blower housing forward to check it - will do today. Didn't check molex connections yet (didn't notice anything on molex bottom receptacle while looking at wire colors, but didn't pull it apart yet either.
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Old 02-20-2014, 01:09 PM   #11
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


I think I finally woke up and see it now (maybe - Per my diagram below, power comes from bottom right terminal of relay (my to bottom-left terminal of speed selector - Then goes to blue wire to molex connector bottom half, then blue wire out of molex male piece (upper half) to blue wire to motor, which runs this blower at medium speed. Correct?
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Wiring new 3-speed motor to old 4 speed motor molex connector wires-400-_ringling_scan_1700x2192.jpg  
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Old 02-20-2014, 04:21 PM   #12
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


Sounds right.
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Old 02-21-2014, 11:33 AM   #13
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


Quote:
Originally Posted by yuri View Post
did you put a brand new capacitor on the motor and is it the correct size? check it with your meter for mfds if you have one.
New capacitor/5uF tested at 4.99 uf, correct size for motor. Checked molex pin connections

Motor would still not start. There was no power at the bottom-left speed selector terminal for the blue (med spd.) wire that goes to motor. This bottom left terminal is supposed to get power from the bottom-rt relay terminal (diagram attached).

There was power at the bottom-right speed selector terminal, which also gets its power from the bottom-right relay terminal, but on a separate wire. This bottom-right speed selector terminal has only an orange wire connected to it, leading to the the molex connector, and on to the orange (med-lo) speed wire which I capped off, because new motor is only a 3-speed (blk, blu, red wires) - old motor was 4-speed.

Since this orange wire connection was used on old motor for med-lo speed (and no other wires attached to this terminal), I couldn't see any risk in connecting the blue wire from bottom-left speed selector terminal to this bottom-right spd. selector terminal that tested @ 120v. No voltage found at bottom-left speed selector terminal. Motor starting and operating normally now - ran furnace through several cycles.

When I got home and was double-checking the diagram again, it finally dawned on me that the separate wire from the relay, connecting to the bottom-left of the speed selector (for the blue wire to motor) must have been bad. Agreed? It's obvious to me now that this wire or connection had to be bad, but I also know that sometimes when "it's obvious to me", that there are possibilities that I don't yet know about that might come into play. In this case however, I couldn't see any "possible unknown possibilities."

I also realize now that the safest thing to do, as far as voltage being constantly present on the capped off orange wire (taped securely back over onto its own wire), would have been to remove its connection on the speed selector block (inside the control box).
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Wiring new 3-speed motor to old 4 speed motor molex connector wires-400-_ringling_scan_1700x2192.jpg  

Last edited by justplumducky; 02-21-2014 at 12:01 PM.
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Old 02-21-2014, 05:57 PM   #14
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Wiring new 3-speed motor to old 4 speed motor molex connector wires


It is very possible.

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