55 F100 6 volt positive ground. The positive ground thing still has my head spinning, and my generator needs rebuilt, so...I am looking strongly into going to 12 volt negative ground. My question right now is about voltage reduction. I have a temp gauge, fuel gauge, battery light, and oil light. If I put a voltage reducer at the temp gauge, and then wire the fuel gauge and lights in series, can I just use that one voltage reducer, or do I need separate reducers? If I wired it in series could I then use the 6 volt bulbs? I think I just need a voltage reducer for the temp gauge, but I am just thinking out loud. Can you hear me now! Thanks..
voltage reducer
- Thread starter tommyleea
- Start date
scicala
Well-known member
When I did my '52 Ford many years ago, I used one factory voltage reducer. I took the wire from the ignition switch that normally powered the gages, and ran it to one side of the voltage reducer, then attached the wire that went to the gages to the other end of the reducer. Mine was an adjustable reducer, and I adjusted it to about 6.2 volts for the gages. Worked great and the gages looked accurate.
Sal
Sal
55blacktie
BANNED
Following Gil Baumgartner's (CTCI, Gil's Garage), I converted my 1955 Thunderbird from 6v to 12v. There was no need to replace gauges or sending units, or use a voltage reducer(other than for the radio, which doesn't work). Don't mix 6v gauges with 12v sending units and vice versa. You will have to replace all 6v bulbs with 12v. If you have other questions, I suggest you read Gil's article.
dmsfrr
Well-known member
tommyleea,
Here's a link to the article....
Doing the 6v positive / 12v negative ground conversion isn't as complicated as you're thinking...
https://www.ctci.org/battery-for-6v-to-12v-conversion/
The '55 Fuel and Temp gauges work on current flow and heat, controlled by bi-metal switching contacts in the senders. They should not be voltage or polarity sensitive, but do need to be a year matched pair in good working condition.
A ballast resistor will need to be added in the existing power wire to the ignition coil, as well as another wire from the new 12v starter solenoid. The ignition coil is polarity sensitive so its leads should be reversed. Diagram below...
If your truck has the battery cable to the starter solenoid on the large left side terminal (not on the right side as shown in the diagram) that's normal, it makes no difference.
If you use a 12v generator you will need to polarize it before starting the truck. The procedure is in the article.
I'm betting getting the 6v generator rebuilt is less expensive than all the new 12v parts you'll need.
If it's just the positive / negative ground thing that's annoying you, you can switch that just by changing the battery cable connections, switching the wires on the ign coil and re-polarizing the generator. On the chance the truck has a functioning 6v radio it may not be polarity sensitive, like the dash clocks are.
If the 6v setup is working well for you there may not be a pressing need to go to 12 volts, unless you're wanting to add 12v accessories to the truck.
One of the bigger shortcomings of some 6v vehicles is having the incorrect size starter and battery cables. They should be zero or 1 guage cables, not anything smaller or they can cause sluggish starting.
.
Attachments
Last edited:
Thanks..I will take a look at the article
Thanks for the info..So it appears I don't need a voltage reducer for the dash gauges, unless they don't work, then add the reducer.
Do I have to run a wire to the I terminal of the starter solenoid? I would like to keep using my push button to start? My ignition switch doesn't have a start position.
dmsfrr
Well-known member
Are the gauges not working now?
If the gauges and senders are working well they should work fine after the 12v change. If there is something wrong with them on 6v, adding a voltage reducer for 12v won't fix them.
Your existing Start switch will connect to the S terminal on the new solenoid just like it does now on the old one.
On a 12v starter solenoid the I terminal powers the Ign coil during cranking for a hotter spark. Diagrams 1 and 2 below.
The engine will start easier with full power to the coil. The ballast resistor powers the ign coil at approx 9v when the engine is 'running' so the coil is much less likely to get too hot, along with the points.
Attachments
Last edited:
Gauges working fine now. Thanks..I ordered a 12 volt generator, voltage regulator, and starter solenoid..Still not sure why I need to run a wire to the I terminal of the solenoid?
Last edited:
The "I" wire sends 12 volts to the coil for starting.
There is a contact inside the solenoid that powers the "I" terminal with full battery voltage when the solenoid is engaged. That voltage by-passes the ballast resistor and allows for a more powerful spark to help with starting. Then, when the solenoid drops out, the coil receives reduced voltage through the ballast circuit.
There is a contact inside the solenoid that powers the "I" terminal with full battery voltage when the solenoid is engaged. That voltage by-passes the ballast resistor and allows for a more powerful spark to help with starting. Then, when the solenoid drops out, the coil receives reduced voltage through the ballast circuit.
Never knew! Thanks..For some reason I thought the ballast took care of all of that.
rotorwrench
Well-known member
I'm not sure I agree with the idea that the stock 6-volt King Seeley coolant temperature and fuel quantity systems will work correctly if a change is made to 12-volts. These units are current based and not resistance based as more modern stuff is. A little heating coil in senders bends the bi-metallic strip to trip the breaker in rapid movement and control the current depending on the position of the diaphragm that applies pressure to change the current output for an indicator reading.
If you are well versed with Ohms law, then you know when you change any one of the variables in basic electricity, it directly affects the other variables. Change the carrier voltage and you change the current draw. Higher voltage tends to decrease the current needed to function a load. This is why a 12-volt system can used smaller wire gauge. This is bound to change the current draw of the little heating coil on the bi-metallic strip. I would question the accuracy of the output of the sending unit.
Ford experimented with this stuff during the first few years of the change over. I believe 1956 was an all 12-volt year for instrumentation but they changed again in 1957 and started using a chopper type voltage regulator on the instrumentation that works in much the same way as a car's voltage regulator does. I've used the solid state constant voltage regulators on King Seeley systems and they work very well. They are small enough that one can be installed on each indicator power supply on the back of the gauge. I'm not real familiar with the 1955 T-birds but all the earlier KS units of the 30s thru most of the 6-volt era, require a voltage reduction for the KS systems to work as intended.
If you are well versed with Ohms law, then you know when you change any one of the variables in basic electricity, it directly affects the other variables. Change the carrier voltage and you change the current draw. Higher voltage tends to decrease the current needed to function a load. This is why a 12-volt system can used smaller wire gauge. This is bound to change the current draw of the little heating coil on the bi-metallic strip. I would question the accuracy of the output of the sending unit.
Ford experimented with this stuff during the first few years of the change over. I believe 1956 was an all 12-volt year for instrumentation but they changed again in 1957 and started using a chopper type voltage regulator on the instrumentation that works in much the same way as a car's voltage regulator does. I've used the solid state constant voltage regulators on King Seeley systems and they work very well. They are small enough that one can be installed on each indicator power supply on the back of the gauge. I'm not real familiar with the 1955 T-birds but all the earlier KS units of the 30s thru most of the 6-volt era, require a voltage reduction for the KS systems to work as intended.
55blacktie
BANNED
I did not replace my 6v gauges, sending units, or starter when converting my 1955 Thunderbird to 12v, and they work. However, my power windows close dangerously fast. The power seat is similarly affected, but I'm the only driver. 12v window and seat motors are not cheap.
Dobie Gillis
Well-known member
Cheaper than 12v motors. They're out of stock at the moment but maybe worth a call.
https://www.vintageautogarage.com/12-volt-to-6-Volt-Window-Top-Seat-Reducer-p/vrwts.htm
https://www.vintageautogarage.com/12-volt-to-6-Volt-Window-Top-Seat-Reducer-p/vrwts.htm
frank long island
Well-known member
also ck your wire harness may consider an upgrade those old cloth covered wires become brittle
I ordered a voltage reducer for my gauges. The T Bird set up might be different than my F100. Thanks
dmsfrr
Well-known member
Yes, when the voltage is increased the current needed to perform the same amount of 'work' is reduced by a corresponding amount. That's why wire for a 6v system is almost double oversized for the same system on 12v.
The rate at which the bi-metal sender contacts open and close may change but the heat-averaged result in gauge needle movement (created by a resistance coil) can be the same.
Having the new voltage reducer on-hand will save time if the gauges do need it. It will be interesting to hear your result.
It is noted on the bottom of the page at the T-Bird link that a voltage reducer (resistor) is sometimes needed.
Many parts were commonly shared between models for efficiency & reduced costs.
Even tho the 'truck' face-plate has a different appearance I would expect the hardware behind it is the same.
A different face-plate would have been a more acceptable solution for the ever-present Bean Counters than having a gauge setup with a different electrical design. Especially since '55 would be the last year for 6v.
.
Last edited:
JeffB2
Well-known member
What you want for your 1955 and earlier Fords is here in step # 13 https://darksidersrealm.forumotion....lt-positive-ground-to-12-volt-negative-ground in the illustration below you can see how to wire it in. https://www.macsautoparts.com/ford_...fb_fJYAqlxHZI7cki58aAiTLEALw_wcB&gclsrc=aw.ds
