yeah, i know this info has been gone over many times, but i am about to do a 12 volt conversion on a 51 chevy, and just wanted to doublecheck and make sure i am doing it the right way......i know that the 6 volt is more than adequate for a 12 volt system, so no wiring changes,,,,,,i know i need to buy 12v headlight bulbs, dash bulbs, dome light bulb, and taillight bulbs,,,,the things i am not completely sure of are: i need a 12v coil,,,i need an alternator,,,and i need some type of resistors for the gauges,,,,,,i think someone once posted the NAPA parts numbers for these,,anyone know?....do i need a seperate resistor for each gauge? anything else i'm overlooking?? any help/tips appreciated....
Yes, get a internally resisted coil and run a one wire alternator or you could run a 12 volt generator if your going for traditional looks. You will need one resistor for each gauge, ie fuel gauge, oil pressure unless you have the old style which runs a pressurized line right to the gauge, the amp (gen) gauge will not need one...12 or 6 volt will work on this. Don't forget to change your gauge bulbs too. good luck sorry don't know the resistor numbers. Found some info on resistors...... These parts are all readily available and if you have a Radio Shack nearby you can use these part numbers: 1ea. 7806, (radio shack # RSU 1392008) $1.49ea. 2ea. 1uF 35v tantalum capacitor (272-1434) $0.59ea. 1ea. Heatsink grease (276-1372) $1.99 1ea. Heatsink (176-1368) $1.49 The most obvious flaw with the 7806 regulator is it's rather limited current output. Unless you are only using it to power a couple gauges, 1 amp might not be enough. The cure is to add a transistor to the output of the regulator. This can increase the output current capability to well over 10 amps using the right transistor and a large enough heatsink. Go here for the link... resistors
The best voltage reducers are the Runtz voltage reducers, I got mine from Speedway Motors. They are a little more pricey, but they work. You will need one for each gauge.
Conversion on the '51 chevy is pretty easy. All your gauges are mechanical except the fuel gauge and ammeter. I think even the clock is mechanical. Like Petejoe said, get an internally resisted coil. One less thing to worry about. Keep an eye on your wiring harness while you're working. Mine ****ed. Even the wires that looked good had really brittle, rotten insulation that flaked off when I moved them. Don't take chances. If you're going to use an alternator, remember you need to change the wiring a little so you can turn your car off. Speedway sells prewired attachments or you can do your own. I've got the diagram somewhere if you need it. Just remember not to turn your old tube radio on afterwards.
There are several ways to do the voltage reduction for your gauges. The voltage regulator setting voltage on almost all 6 volt vehicles is 7.2 volts. If the gauges do not have a constant voltage regulator they were designed to operate at this voltage. The only gauges I know of that had a constant voltage regulator are Kaiser 5 volt regulators, Ford 12 volt systems with the 6 volt regulator and some Chryslers with 5 volt regulators. Some people use these for applications like yours but they were designed to put out 5 or 6 volts not 7.2. The 7806 regulator will give you a constant 6 volts. The Runtz is this regulator attached to a mounting strip and pre wired for your convenience. So if you dont mind wiring it up yourself you can buy them for less than 2 bucks at Radio Shack. Will the gauges work ok Yes, they will work, but they wont be factory accurate Would 55 or 60 year old gauges be any more accurate if they were powered as designed Who knows I havent tested them so I sure as hell dont. But Im one of those that believes you need to do it the way it was designed to work. There is a voltage spike phenomenon that can occur with a vehicle with an alternator if there is a large load that is suddenly dropped or turned off (such as the instant that a fuse blows) that will fry a discrete semiconductor like the 7806. It will also fry your cell phone if its plugged in to charge with a cheap charger. Most of the time it will cause the transistor to "open" which is not a problem, but I've seen them short "closed" which will send 12 volts to the gauge. Not a good thing for some gauges.... The diode (below) will not do this since they tend to "leak" a little. Ive found a diode that puts out 7.2 volts if it is supplied with 10 to 18 volts. It too can handle up to 1 amp. It will cost you $ 3.00. To date Ive sold several thousand and havent had any complaints other than the occasional idiot who wires them up backwards and the guy who tried to run his heater blower motor on one. Hambrs who purchase 3 or more and pay with check, cash or money order will get them shipped free. I also have a 1-ohm resistor that will handle the heater blower motors real well. Theyll handle power seat and 6 volt hydraulic motors as well. They are $ 27.50 each for Hambrs and includes shipping. The 1.5-ohm resistors work best for wiper motors and window motors Hambrs price is $ 20.00 with shipping. As for the coil you need a total resistance of around 3 ohms as measured between the power source + and the points ( post on the coil). Most 6 volt coils have a resistance of 1.2 ohms. If you add a ballast resistor of 1.5 to 1.8 Ohms such as a NAPA P/N ICR13 you dont have to replace the coil. I stock the 1.5 Ohm Chrysler style resistors at the Hamb'r price of $ 5.00 each. If you do replace the coil make sure it has the proper resistance such as a NAPA P/N IC14 or Delco P/N U515. If you are keeping the 6 volt starter make sure you change the solenoid to a 12 volt unit or you will be changing it in a parking lot. Clocks are best converted to a 12 volt quartz movement. Email me for a list of people who do this work. 6 volt radios are not worth fooling with. You would need to replace all of the capacitors and the ******** for one to work right. Custom Autosound makes some great units that will bolt right in your dash. They even have controllers for trunk or under seat mounted CD changers. Al
thanks for all the information,,it'll be very helpful......didn't even think about the solenoid,thanks for that one...
[ QUOTE ] 6 volt radios are not worth fooling with. [/ QUOTE ] If you do decide to fool around with an old radio here's the link to adapt it to 12 volts. bilb
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