Parts needed with switch to 12 volt system

5

53vicki

Junior Member
Switched our 53 Vicki to 12 volt. Can someone please tell me if we need to swap out the following parts since doing the conversion to 12v;

1. brake stop light switch
2. turn signal flasher
3. horn relay

Also how easily are the fuel, temp & oil pressure gauges damaged if you run the car without using a reducer ?

thanks-
 
You brake light switch is ok.
You flasher can will likely need to be changed to match the wattage of your new 12 volt bulbs.
Your horn relay may cope, depending on how long you toot for. The horn will likely cope, as will your starter. I have heard mention of a "soft starter" to remove the viciousness of the 12v applied to the 6 volt starter.
The gauges need resistors, apparently they each need their own.
A chat with an older Auto electrician will confirm or negate these comments.
Welcome! btw.
 
Here is an excellent guide and MUST READ:http://www.ebay.com/gds/6-to-12-Volt-Conversion-1955-Ford-/10000000001571127/g.html Ford used 6 volt gauges up to the early 80's here is the gauge regulator mentioned which will take care of them all:http://www.ebay.com/itm/1966-1969-Ford-Instrument-Voltage-Regulator-Solid-State-Electronic-5v-/280742901929?pt=Vintage_Car_Truck_Parts_Accessories&fits=Model%3AMustang&hash=item415d94b8a9&vxp=mtr Need more advice from guys that have done it a lot? Join us here:http://www.jalopyjournal.com/forum/group.php?groupid=332
 
Hi there, you must use a voltage reducer on your gauges. When you double the voltage you double the current in amps on any given electrical item. Double the current through those fine gauge windings and they will burn out. Now some will say they have run 6 volt gauges on 12 volts for years and all l can say about that is they got real lucky. DONT TRY IT EVEN FOR ONE MINUTE. All relays should be changed to 12 volt. Horns pull high current (20 amps + each ) and double that if used on 12 volts. Better to use a large resistor in series with each horn or fit 12 volt horns. Flasher can needs to be 12 volt unit also and match the wattage of the two 12 volt flasher globes combined. Generator and voltage regulator needs to be upgraded to a 12 volt unit or maybee an alternator. If car has a starter solenoid fitted this should be changed to 12 volts also. All other manually operated switches will be OK. Regards, Kevin.
 
I may have missed something but I was always taught that the voltage and amperage were inversely proportional. IOW if voltage is doubled, amperage is halfved. Thats why 12 V systems have smaller gauge wiring. There's a guy that advertises in Hemmings that puts out a good guide for this conversion, and sells the proper resisters for the gauges. I'll look him up and post later.
 
Check e-Bay for the gauge resistors. There's a couple of different ones on there that send the power to all the gauges. I've never had good luck with the Runtz style resistors and you need to put one on each gauge.
 
koates said:
Hi there, you must use a voltage reducer on your gauges. When you double the voltage you double the current in amps on any given electrical item. Double the current through those fine gauge windings and they will burn out. Now some will say they have run 6 volt gauges on 12 volts for years and all l can say about that is they got real lucky. DONT TRY IT EVEN FOR ONE MINUTE. All relays should be changed to 12 volt. Horns pull high current (20 amps + each ) and double that if used on 12 volts. Better to use a large resistor in series with each horn or fit 12 volt horns. Flasher can needs to be 12 volt unit also and match the wattage of the two 12 volt flasher globes combined. Generator and voltage regulator needs to be upgraded to a 12 volt unit or maybee an alternator. If car has a starter solenoid fitted this should be changed to 12 volts also. All other manually operated switches will be OK. Regards, Kevin.
Click to expand...

Doubling the voltage doesn't double the current, it halves it.
 
koates>>>When you double the voltage you double the current in amps on any given electrical item. Double the current through those fine gauge windings and they will burn out.>>>

As stated, koates is correct. It assumes the resistance doesn't change for any given device when going from 6 to 12 volts. I = E/R

Jack E/NJ
 
This may be a bit premature, but be sure and check out this site for cool burning LED replacement bulbs. It's amazing how much brighter they are and they are cool to the touch.
http://www.superbrightleds.com/
 
Most 6v starters can easily gobble up as many amps as a 12v battery can dish out without suffering indigestion.

Jack E/NJ
 
Jack E/NJ said:
koates>>>When you double the voltage you double the current in amps on any given electrical item. Double the current through those fine gauge windings and they will burn out.>>>

As stated, koates is correct. It assumes the resistance doesn't change for any given device when going from 6 to 12 volts. I = E/R

Jack E/NJ
Click to expand...

No.
If the item has 12 ohms resistance, at 6 volts it will pull 2 amps. At 12 volts it will pull 1 amp.

That being said, the gauges still need reducers to read accurately.
 
Sorry, koates is still correct. E=IR. Thus I=E/R. So in your 12 ohm resistance example
I (@ 6v) = 6v/12 ohms = 0.5 amp
and
I (@ 12v) = 12v/12ohms = 1 amp

Jack E/NJ
 
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance,[1] one arrives at the usual mathematical equation that describes this relationship:[2]
I = \frac{V}{R},
where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[3]
The above is from wiki.

thought of like water:
If you double the pressure (voltage) you double the flow(amperage) for a given resistance (restriction to the flow)

Koates is correct
 
The “local” and “online” experts may tell you, that you need to add a “shunt” to your original amp gauge when you upgrade to a modern alternator type of charging system. You do not and here is why….

An amp gauge does not measure alternator output it measures the amount of current going into or coming out of the battery.

The advantage of the alternator is the ability to provide an output at idl...e and low rpms (something the generator could not do) to keep the lights bright and the battery fully charged. The total electrical load of the vehicle remains the same as it was before.

If you read the Alternator Gazette you know the average 6-volt car has an electrical load of about 36 amps with everything turned on.
The total amount of amperage passing thru your dash gauge will be the same or less with the alternator because the alternator is keeping up with the electrical load at all times. With the battery always fully charged at all times no large amounts of current will be flowing into or out of the battery as before.

The total amount of amperage passing thru your dash gauge will be the same or less with the alternator because the alternator is keeping up with the electrical load at all times. With the battery always fully charged at all times no large amounts of current will be flowing into or out of the battery as before.

Upgrading to 12-volts…

Now suppose you decide to upgrade to 12-volts and install a 12-volt 60-amp alternator, so you can add a modern stereo and air conditioning. What happens to the total electrical load then?

The total electrical load becomes half of what it was originally because of the electrical rule that says when you double the voltage the amperage load will be reduced by half. So our 36 amp electrical load becomes 18 amps on 12 volts. Do you think you can run air conditioning and a stereo on the remaining 18 amps? Absolutely!

You have plenty of reserve output from the alternator (40 amps, 60 minus18) and the only current that will flow thru the amp gauge in the dash is what is needed to keep the battery fully charged just as before.

*** The alternator will take care of the additional electrical load with no affect on the amp gauge or battery.***
 
53vicki>>>Also how easily are the fuel, temp & oil pressure gauges damaged if you run the car without using a reducer ?>>>

You need an appropriate 'reducer', otherwise known as a resistor, series connected to each 6v guage when switching to 12v. Each reducer will be approximately the same resistance and handle the same power as each 6v guage so that the amps and the power dissipation thru the guage itself will be approximately the same at 12v as it was at 6v.

If you aren't too electrically-inclined, I suggest you purchase these needed guage voltage reducers from your favorite early v8 vendor.

Jack E/NJ
 
Mr Alternator, you said,
'An amp gauge does not measure alternator output it measures the amount of current going into or coming out of the battery.'
Surely this depends on how the set up is wired?
To me, the ammeter (ampmeter) measures the current that is directed through it.
May be I'm slow, so can you expand on the statement.

An alternator will produce it's rated output eg a 55amp alternator will produce 55amps (or else it has something wrong with it)
 
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