ARE THEY POLARITY SENSITIVE?

[Seaside Pete]

Hi Guys

 

Just purchased a voltage converter 12v to 6v that will handle up to 10amp which I am going to use for the fuel gauge and heater fan instead of a runtz type resistor (fuel gauge). my question is as the car is now neg earth instead of pos do I need to change anything ie: will the heater fan run the other way or anything like that?

 

Thanks in advance.

 

Pete

 

 

[Plymouthy Adams]

the fan motor is not a permanent magnet motor...so the motor is not polarity sensitive..

[YukonJack]

You shouldn't need a voltage reducer for the fuel gauge. I've been running my gauge on 12 volts for about 9 years.

[mopar_earl]

You shouldn't need a voltage reducer for the fuel gauge. I've been running my gauge on 12 volts for about 9 years.

I agree. Fuel gauge works on resistance, not voltage.

Earl

[TodFitch]

You shouldn't need a voltage reducer for the fuel gauge. I've been running my gauge on 12 volts for about 9 years.

 

 

I agree. Fuel gauge works on resistance, not voltage.

Earl

 

 

Except that the dash unit could have some wiring that can't handle twice the current without significantly reducing its life. I'd play it safe and feed it the voltage it was designed for.

[Plymouthy Adams]

the fuel gauge is voltage operated ...the internal of the gauge has a built in voltage regulator that is designed to regulate the circuit at 5.0 volts  the application of 12 volts cycles this thermo regulator at a higher cycling rate and can in some cases cause a slight flicker of the gauge needle.  The 5 volt regulated voltage is then sent to the resistor of the sending unit in the tank by the two individual wires A and B...each of these legs is pulled to ground by the dividing of the 0-30 ohms to ground via the common wiper contact which is your single grounding point at the rear...this differential pulls the gauge toward full and toward empty at the same time thus providing an accurate and rock steady reading.  That is the very reason that the two wire system is sensitive to correct wiring of Batt, A and B wires from gauge to sender.

[48mirage]

You may find the 10 amp voltage reducer is a little small.  It is big enough to operate but it is the starting amps that may cause you a problem.  The folks at www.Koolcars.us sell some larger ones.  Another and probably better option is to go to a 12 volt fan motor.  The original thread is gone but you might  do a search for NAPA 655-1022.  There is a thread about it working in a 47 Plymouth and I used the same in my 49 Dodge.

[Don Coatney]

12 volt bolt in heater motor.

 

 

 

[mopar_earl]

Except that the dash unit could have some wiring that can't handle twice the current without significantly reducing its life. I'd play it safe and feed it the voltage it was designed for.

Twice the amps? Higher the voltage the lower the amp draw. Ohms law. That's why 6v has a lot bigger battery cables and wiring than 12v. That's why you can convert to 12v and not have to change wiring gauge.

Earl

[mopar_earl]

the fuel gauge is voltage operated ...the internal of the gauge has a built in voltage regulator that is designed to regulate the circuit at 5.0 volts the application of 12 volts cycles this thermo regulator at a higher cycling rate and can in some cases cause a slight flicker of the gauge needle. The 5 volt regulated voltage is then sent to the resistor of the sending unit in the tank by the two individual wires A and B...each of these legs is pulled to ground by the dividing of the 0-30 ohms to ground via the common wiper contact which is your single grounding point at the rear...this differential pulls the gauge toward full and toward empty at the same time thus providing an accurate and rock steady reading. That is the very reason that the two wire system is sensitive to correct wiring of Batt, A and B wires from gauge to sender.

Very good write up. I agree. You can run 6 or 12 volts to the fuel gauge as we both stated. You went into detail, which I like.

Earl

[mopar_earl]

You may find the 10 amp voltage reducer is a little small. It is big enough to operate but it is the starting amps that may cause you a problem. The folks at www.Koolcars.us sell some larger ones. Another and probably better option is to go to a 12 volt fan motor. The original thread is gone but you might do a search for NAPA 655-1022. There is a thread about it working in a 47 Plymouth and I used the same in my 49 Dodge.

I agree, a 6v motor is going to pull some amps. I have my doubts 10 amps will be enough.

Earl

[Seaside Pete]

12 volt bolt in heater motor.

 

 

 

 

 

Don

 

My heater is not the same as yours (please see pic), so I am not sure if the same motor would fit? I have emailed Siemens here in the UK and asked about the motor that you have suggested as they do not list that part number but, they have not replied.

 

In addition if I change the motor for a 12v will I need to change or have any problems with the 3 stage fan switch (please also see pic) as it seems to have 2 resistor type things attached I assume to reduce/increase voltage to adjust the fan speed?

 

 

Pete

Edited April 29, 2015 by Seaside Pete

[Don Coatney]

I don't know if the resistor switch will work. I will use my fan motor as either on or off.

[Andydodge]

Pete.........I have had a resistor attached to the fuel guage for the past 42 yrs without a problem, the cars been 12 volts, negative earth since 1973.........the fuel guage is the only one that has had any change, just the resistor, nothing fancy, the amp guage reads amps, and the water/oil are mechanical.........and if the fan is 12 volts then it should be fine.......andyd.

[Adam H P15 D30]

Don

 

My heater is not the same as yours (please see pic), so I am not sure if the same motor would fit? I have emailed Siemens here in the UK and asked about the motor that you have suggested as they do not list that part number but, they have not replied.

 

In addition if I change the motor for a 12v will I need to change or have any problems with the 3 stage fan switch (please also see pic) as it seems to have 2 resistor type things attached I assume to reduce/increase voltage to adjust the fan speed?

 

 

Pete

My resisted switch on my 49 controls my 12v heater motor just fine. Has a medium and high. Btw I used a heater motor out of a 64 Dart because it's what I had lying around. I figure those motors are pretty much universal except shaft length and diameter. Probably be able to find a replacement quickly.

To add to the list of items not needing a reducer, I have been running my clock on 12v for years now with no problems. Just winds a little faster.

[Seaside Pete]

Just wiring up the 6v fan to the 12v to 6v converter and before I switched the fan on I thought I would run a meter across to see how many amps draw there was but before I did that I thought I would also check out the 3 stage switch with a test light, It worked fine ie: live feed in, nothing coming out, switch it on live coming out on all 3 stages. However connect the fan feed wire from the switch and the fan runs straight away with no actual feed from the switch, turn the switch on and the fan stops. As I thought the fan was not polarity sensitive I am a bit stumped so any help would be great. By the way the fan seams to be drawing about 6 - 7 amps and as it's a 3 stage switch I think the slow setting most prob takes care of the start spike so doesn't blow the 10 amp fuse.

 

Thanks

 

Pete