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Old 09-21-2018, 12:53 AM   #1
Paul Bennett
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Default After polarity change with 12v conversion the heater becomes an air conditioner

My pending 12v conversion: - bulbs - no problem ... gauges - no problem battery and alternator done and done.

The two external wires for the heater motor dual fan speeds are easily accessed.

Does anyone have a 50 Merc heater motor apart enough to tell me about the motor common wire? I.e. How can I gain access without removing the motor? Please talk to me or provide a photo.
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Old 09-21-2018, 12:55 AM   #2
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

Original 6 volt heater motor?
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Old 09-21-2018, 12:58 AM   #3
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

You probably need to either update the heater motor (not an engine) to 12v or run a runtz or a 54-57 ford ceramic resistor. Fan is running double time on 12v.

To me it's a voltage issue, as it draws the same amps... well twice the amps as its working twice as fast.


Think of it this way, trying to get a nice glass of water out of a fire hydrant that's open. Same idea that you can put a 9v battery on your tongue to check if its okay to put in your fire alarm, but you would not want to put a 110v cord there either. ac or dc current.


you can check the wires with a 6v battery and some wires....


motor doesn't care about polarity. if so a 6v starter would run in reverse on 12v. It figures it out on the fly.











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Last edited by Tinker; 09-21-2018 at 02:09 AM.
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Old 09-21-2018, 01:48 AM   #4
51 MERC-CT
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

Have not done a thing to my original 6 volt '51 Merc heater motor.
It just runs faster on both speeds while operating on 12 volt neg. ground.
Sorta' like my original 6 volt starter motor has done for the last 25+ years while operating on 12 volts.
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Old 09-21-2018, 01:56 AM   #5
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

well there ya go. its a testament to these old components that were over built to handle more then designed.
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Old 09-21-2018, 04:03 AM   #6
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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The polarity change makes the fan go opposite direction.
The ones that have reverse operation for defrost is easiest to adapt...thoose you can just swap around the wires at the switch...or just use defrost on the knob as heat...
The fan is most effective at a certain rpm...so rewing it up higher may or may not give you more airflow.
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Old 09-21-2018, 05:23 AM   #7
51 MERC-CT
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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Originally Posted by flatheadmurre View Post
The polarity change makes the fan go opposite direction.
The ones that have reverse operation for defrost is easiest to adapt...thoose you can just swap around the wires at the switch...or just use defrost on the knob as heat...
The fan is most effective at a certain rpm...so rewing it up higher may or may not give you more airflow.
Nonsense, reversing the polarity does NOT reverse the rotation of the fan motor or the starter motor.
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Old 09-21-2018, 05:29 AM   #8
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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Originally Posted by flatheadmurre View Post
The polarity change makes the fan go opposite direction.
The ones that have reverse operation for defrost is easiest to adapt...thoose you can just swap around the wires at the switch...or just use defrost on the knob as heat...
The fan is most effective at a certain rpm...so rewing it up higher may or may not give you more airflow.

Really???
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Old 09-21-2018, 06:02 AM   #9
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

Thanks for the chuckle. What I do not know about electrical systems in vehicles unfortunately for me fills just about every book ever written on the subject. The temperature where I live has been in the very unseasonable 90's for several weeks, even on the periphery of Hurricane Florence. I wish I could figure out a way to make the heater into an air conditioner. I have been working on a way to convert lead into gold as well but it's getting difficult to find much lead to experiment with these days and I don't want to melt it out of the body seams.
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Old 09-21-2018, 06:30 AM   #10
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

If rotor & stator are electromagnets, it won't reverse. If one is a permanent magnet, it will. Jack E/NJ
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Old 09-21-2018, 06:39 AM   #11
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

My question is, does the horn suck?
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Old 09-21-2018, 07:02 AM   #12
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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My question is, does the horn suck?
Other than adding a 12 volt relay it gets more attention
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Old 09-21-2018, 07:26 AM   #13
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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Really???
in fact, after a fan reaches its max rpm-cfm its cfm can actually drop increasing rpm.
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Old 09-21-2018, 09:18 AM   #14
Jack E/NJ
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

Yeah, but the big question is does the same thing happen when you add, multiply or divide rpm & cfm? 8^) Jack E/NJ
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Old 09-21-2018, 11:36 AM   #15
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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Originally Posted by Jack E/NJ View Post
Yeah, but the big question is does the same thing happen when you add, multiply or divide rpm & cfm? 8^) Jack E/NJ
cfm is directly related to rpm but only to a point where max fan cfm is achieved. a fan producing 100cfm at 1800rpm will produce about 50 cfm at 900rpm. there are what are known as the fan laws. i used to know these quite well but have forgotten much. Mark
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Old 09-21-2018, 02:27 PM   #16
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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cfm is directly related to rpm but only to a point where max fan cfm is achieved. a fan producing 100cfm at 1800rpm will produce about 50 cfm at 900rpm. there are what are known as the fan laws. i used to know these quite well but have forgotten much. Mark
And how does that translate to 'squirrel cage blowers' ?
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Old 09-22-2018, 10:45 AM   #17
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

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Originally Posted by flatheadmurre View Post
The polarity change makes the fan go opposite direction.
The ones that have reverse operation for defrost is easiest to adapt...thoose you can just swap around the wires at the switch...or just use defrost on the knob as heat...
The fan is most effective at a certain rpm...so rewing it up higher may or may not give you more airflow.
Second the reversal but you may need a different reastat. G.M.
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Old 09-22-2018, 03:59 PM   #18
Paul Bennett
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

Polarity change doesn't affect rotation for these types of motors - I didn't consider the starter situation. ME BAD Obviously looking for a problem which doesn't exist.


Thanks for wiseing me up.
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Old 09-22-2018, 04:02 PM   #19
runewilliam_merc
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Default Re: After polarity change with 12v conversion the heater becomes an air conditioner

Hi!

Om my 1952 Mercury Custom, I went to my local Mustang parts dealer with the 6v defroster assembly. The guy behind the counter looked at it for about five seconds, put his hand into a shelf, and pulled out a motor for a 1965(?) Mustang.
The output shaft had larger diameter, so I put the hamster wheel in a lathe and drilled a bigger hole so that it would fit.
Assembled the parts and put it in my car, it worked flawlessly.

Rune
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