help from electrical gurus

[JSabah]

I'm changing my car ('49 Ply)  from 6v to 12v.  I have most figured out but am a little confused when it comes to the heater blower fan motor and the defroster blower motors.  I have a fresh 6V battery and double checked the voltage with my multi-meter.  Then I connected 1 fan at a time with my multi-meter in between set at 10A setting and got the amperage draw (both at startup and running )  I also checked the resistance across the motor.  These are the results:

 

Blower Motor 3 amp (5.74 Amp @ startup)  2.8 Ohms

Defroster Motor 1.38 Amp (1.69 Amp @ startup) 2 ohms

 

This doesn't seem to me to be too big of a draw to use a voltage regulator  BUT  almost everything I read says that fan motors have too big a draw to successfully use a voltage reducer.   I found the following which is described for fan motors and looks to me (not saying much) to be a viable alternative than finding new motors (both of mine work fine):

https://www.speedwaymotors.com/Electric-12-Volt-to-6-Volt-Reducer-for-Motors,15824.html.

 

Im not sure but this looks to have the same specs (although there are variations that frankly I dont understand) and is 1/3 the price:

https://www.alliedelec.com/product/vishay-dale/rh0506r000fe02/70201528/?gclid=EAIaIQobChMIqeH0vd7J5AIVj8JkCh0VPgcCEAQYASABEgKSuPD_BwE

 

 

Being in So Cal, I don't expect to need to use the heaters too often, but you never know and I'd like everything to work ...without starting a fire.  Will the 2nd item work?

Thanks

[Los_Control]

What about the original 6 volt motor?

You may be able to get 3 or 4 years from it?

Your car is pretty nice, I understand wanting to get exact replacement parts.

 

Your 6 volt motor is simply going to run faster.

Eventually years down the road, when you run the heater to much in LA, you just replace it with a 12 volt heater motor the same size.

You can do that now.

 

Just wondering if you are over thinking the non issue.

 

Just pull your motor out, size shape, mount, voltage and buy what you want. 

Restoring a heater, is a totally different topic on its own, being from LA you get a pass, but it is just another step you need to do.

 

[JSabah]

Thanks for the "pass".  I am planning on using the 6v motors (even though what I read says to change them because voltage reducers don't work/last/???).  I just thought that for somewhere between $6-$18/ea, I could save the trouble of having  having to change burned out motors in a few years by reducing the voltage to them from 12V  (new system) to 6 v ...since the draw/amps dont seem to be very high.

[Sniper]

It's nothing more than a wire wound resistor.  Since you know the resistance of your motors you need a resistor that is approximately the same resistance to drop the voltage in half.

 

https://www.amazon.com/Aluminum-Shell-Housed-Wirewound-Resistor/dp/B06ZZGBHGX/ref=sr_1_36?keywords=3+ohm+resistor&qid=1568251203&sr=8-36

 

$3. wire it in series with the input to your motor.

[Los_Control]

my only point, is a simple motor . Just pick the size  & shape, get one off of ebay for less then $20.

Same time, your current 6 volt motor may last a few years on 12 volts. It will just turn faster.

It just depends on how much you use your heater in Southern CA.

 

Same time, these little motors have the same physical and mounting options. They are offered in 6 or 12 volt. Just pick the one you need and order it.

Myself, I would replace that little motor the first time it fails.

[Greenbomb]

Speedway probably stocks about a dozen and Allied probably has hundreds, thus the price difference. (Speedway might even get theirs from Allied!) Both units appear to have the same specs, so either should do. “They” say the resistors get really hot in use; maybe you should go with a higher wattage unit. Same voltage and current ratings and ohmic values, but higher watt rating to handle/dissipate the heat. And mount it on a heat sink of some kind (hunk of aluminum flat bar) where it will get some air flow. Use heat sink compound, also.

[maok]

As been mentioned, the fans will turn faster, the current (amps) will be about the same. For the little use they will get I would just run them on 12 volts. Stick a 10amp fuse inline.

[kencombs]

Lots of cars/trucks have used a single speed motor with different speeds accomplished with  a variable resistor.  Others have used multiple resistors selected with the switch to offer different fixed speeds. 

The point of this is that they all did the same thing to keep the resistors from burning out.  They placed them in the airflow of the heater, inside the duct downstream of the blower. 

You can copy that design to handle the heat of a resistor of your choice.

[greg g]

Typically heater fan motors have  built in resistor to give you the two or three speeds, high speed is the only one that gets full voltage.  Test the switch out put with your volt meter.  You will likely get some things like 3 5 and 6 volts.. then hook the switch to 12 v bet you get t something like 5 8, and 12.  So if when you go 12 volts, if  you only use the first two positions you shouldn't have a problem.  The six volt motors wires and switches are robust enough to deal with that, only thing to watch is more heat from the resistance coil in the switch.

[Adam H P15 D30]

12v motors are a inexpensive, permanent, almost bolt in fix.  Why mess with smokin hot resistors and such, do it right.  I used a mid- 60's Dart, had to trim the shaft a little.

Don't mean to be blunt but camon?

[Sharps40]

Often the resistance coils went in the plenum to keep them from overheating on both 6v and 12v models.

 

But....since the ballast resister on the 60s model mopars (to drop 12v to 6v for the Dizzy once the ballast warms up) ran hot continuously for years without burning out.....maybe try mounting on on the firewall in the wind.   Hook up the heater, you'll get 12v for a bit till the resister warms, then it should drop the volts.

 

Or just do it easy and run the 6v motor as is.  

[Dan Hiebert]

Not an issue worth overthinking in my book.  Option 1 - A voltage reducer will keep the 6v motors alive for a long time.  Keep in mind they simply were not engineered to run as fast as or as hot as they will with 12v, and will burn out after a while if not run off of a reducer.  If you don't want the added accouterment of a reducer behind the dash for whatever reason; Option 2 - it is relatively simple to retrofit 12v motors and not worry about voltage reduction or amperage.  The hardest part is getting the counter guy/gal to find the right motor for you. 

[Sniper]

A number of people say retrofitting a 12v motor is "easy".  Got a source for these motors?  Try Ebay isn't helpful.

I am in the process of converting my 51 Cambridge to 12v.  Need a wiper motor too.

[kencombs]

5 hours ago, Sharps40 said:

Often the resistance coils went in the plenum to keep them from overheating on both 6v and 12v models.

 

But....since the ballast resister on the 60s model mopars (to drop 12v to 6v for the Dizzy once the ballast warms up) ran hot continuously for years without burning out.....maybe try mounting on on the firewall in the wind.   Hook up the heater, you'll get 12v for a bit till the resister warms, then it should drop the volts.

 

Or just do it easy and run the 6v motor as is.  

That's true abut the ballast.  But, one of the most common complaints back in the day was 'my car will start, but die when i release the starter'. Saw a lot of those in Dad's shop/salvage.   LOTS of those things where changed due to failure.  I drove Mopar V8s from the mid 60s and well into the 80s.  I kept a spare in the car at all times.simpl

 

Plenum mounting I mentioned earlier is a simple, reasonable precaution.

[JSabah]

Thanks for all your input. I decided to try to step the voltage down, but also decided to try t make a heat sink out of some copper scrap I had laying around (I did buy some heat compound).  Since the fan was out of the car it was pretty easy to put it in the plenum. Just had to drill some holes and use some grommets so the wires won’t wear. I think this should last. 

[Sniper]

I found that a heater blower for a 65 Plymouth Barracuda with factory AC looks like it may work, I have one on order and will update as I find things out.

[Tim Larson]

On 9/20/2019 at 6:12 PM, JSabah said:

Thanks for all your input. I decided to try to step the voltage down, but also decided to try t make a heat sink out of some copper scrap I had laying around (I did buy some heat compound).  Since the fan was out of the car it was pretty easy to put it in the plenum. Just had to drill some holes and use some grommets so the wires won’t wear. I think this should last. 

 

I'm curious which resistor you ended up choosing. My '49 was converted to 12 volt, but I don't think the blower motor was changed. 

[JSabah]

7 hours ago, tjlarson88 said:

 

I'm curious which resistor you ended up choosing. My '49 was converted to 12 volt, but I don't think the blower motor was changed. 

I believe that the two I listed in the 1st post are the same so I got them from Allied as it cost a few dollars less ... and that is what they seem to specialize in (electrical components) 

 

https://www.alliedelec.com/product/vishay-dale/rh0506r000fe02/70201528/?gclid=EAIaIQobChMIqeH0vd7J5AIVj8JkCh0VPgcCEAQYASABEgKSuPD_BwE

[maok]

29 minutes ago, JSabah said:

I believe that the two I listed in the 1st post are the same so I got them from Allied as it cost a few dollars less ... and that is what they seem to specialize in (electrical components) 

 

https://www.alliedelec.com/product/vishay-dale/rh0506r000fe02/70201528/?gclid=EAIaIQobChMIqeH0vd7J5AIVj8JkCh0VPgcCEAQYASABEgKSuPD_BwE

 

Why did you choose a 6 ohm resistor?

[JSabah]

Good question. Since Electronics is not my strong suit so I looked at this several ways.  

 

1st, I used my meter and Ohms Law and tried to figure it out mathematically (look at first post). 

 

2nd I read and searched the web

 

3rd I saw that Speedway motors advertised this for this purpose 

 

Looked up the part number from the picture and found it on the Allied webpage so I could see all the options and specs. 20W seemed fairly large and it was the largest available before a large jump in price (100w)

 

all the above pointed to the part I bought. That being said, I won’t really know if it works until I drive this car on the coldest day we have in So Cal .... so.... May never know ? 

[maok]

FYI, Ohms laws doesn't work well when there is an electric motor in the circuit. The current (amps) draw is directly related to the mechanical resistance to the motor ie., the fan air resistance. You will find the current (amps) draw will be very similar when connected with 6 or 12 volts, yeah I know, it doesn't sound right. The higher voltage will spin the fan faster.

 

You may have to experiment with a few resistor values to get the speed correct if the fan speed is important to you.

[Sniper]

at 12V 20W is less that 2 amps, might be small.

[JSabah]

14 hours ago, Sniper said:

at 12V 20W is less that 2 amps, might be small.

You are correct... I miss typed. The part I’m trying is 50w max. 

[bobus8]

Wattage is calculated by multiplying voltage times amperage.  Also, if you are running 12 volt system, your battery is probably charging at 14 vdc.  Using 14 as your voltage and applying 10 amp as maximum wattage (if motors are stalled), you are looking at a 10 ohm 140 watt resister.  You can probably get away with a lot less wattage than this.  Just so you know, you can put two 20 ohm resisters of 50 watts each in parallel (wired beside each other)  to get a 100 watt 10 ohm setup which might be all you need.  Of course you can lower the ohms rating for more power if needed.

[Sniper]

On 9/21/2019 at 7:28 PM, Sniper said:

I found that a heater blower for a 65 Plymouth Barracuda with factory AC looks like it may work, I have one on order and will update as I find things out.

 

Since those that claim to have updated their blower motor to a 12v version haven't stepped up to tell us what motor they used, beyond some generic "look on ebay" comment, I sorted it out. 

 

At least for a 1951 Plymouth Cambridge.  Not sure what else it may apply to.  Though I suspect most if not all of them.  Wrote it up on my webpage.

 

http://www.im-creator.com/free/yourolddad/the-snipers-nest/blower-motor