49 Roadmaster 6V and 12v system combined.

R

Reckless

Member
OK i have a 49 Roadmaster and I need 12v for the electronic ignition, Air conditioning and the air-bags. I have no issues with the 6 volt system and it is in prime condition. Having a few mates that are electrical guys we've sat down and nutted out a wiring diagram that gives me 12v and 6v.

This involves a minimal amount of work and not too many parts.

Parts list
1. 12v alternator
2. second 6v battery (Optima style batteries are used as two will fit in the stock battery tray) 180CCA works fine
3. one 6v relay
4. one 12v accessories relay (whatever amperage you need for your accessories)
5. fuse block
6. oil pressure switch ( this is a second safety for the foot ignition system, if oil pressure is present the pressure switch will open circuit and the starter will not be able to crank)

Parts to throw over your shoulder are the generator, old ignition coil and the regulator.

I've marked up a wiring diagram as my car is built, i have a 6v fuel pump, HEI ignition and converted the reverse lights to indicators. Apart from that a stock 49 roadmaster.
Visio-bUICK SPARKS-page-001.jpg
 
that's an elegant solution, a car that can run 6v or 12v as desired.


you're probably going to confuse the hell out of any subsequent owners who try to do maintenance on this though.:D
 
Reckless, congrats on coming up with an extremely well-thought-out 12V conversion. It was a brilliant idea to use an oil pressure switch for the starter. I wish I had thought of that when I did mine.

I do have a couple of questions though:

1. Why was it necessary to use a second relay to feed the 12V fuse block? Are 6V relays not available with a sufficiently high contact rating?

2. I am not understanding your comment about converting the reverse lamps to indicators. On your diagram it looks like the reverse lamps are still working as reverse lamps and you installed an additional set of lamps to serve as rear turn signals. Why was this necessary?

Ray
 
49FLAMER said:
can't you just change the whole thing to 12 ?
Click to expand...

You can but its a lot more work and you end up modifying an awful lot of the car from original. I couldn't bring myself to do it as the car I have, the wiring under the dash still looks brand new and everything works fine so why change it. My goal was to provide 12v for a few of the items i wish to add to the car as i had no problem with the original system. If you had a car that was in poor condition electrically i would do a complete conversion to 12v as you have all the work to do anyway.
 
raycow said:
Reckless, congrats on coming up with an extremely well-thought-out 12V conversion. It was a brilliant idea to use an oil pressure switch for the starter. I wish I had thought of that when I did mine.

I do have a couple of questions though:

1. Why was it necessary to use a second relay to feed the 12V fuse block? Are 6V relays not available with a sufficiently high contact rating?

2. I am not understanding your comment about converting the reverse lamps to indicators. On your diagram it looks like the reverse lamps are still working as reverse lamps and you installed an additional set of lamps to serve as rear turn signals. Why was this necessary?

Ray
Click to expand...

Hi Ray

Thanks for the nod of approval.

I couldn't find a 6v coil relay for the current i need ( 12v air compressor for the airbags) so yes thats the reason. If you didnt have those demands then you could ditch the 12v coil relay.

As for the reverse lamps ive mounted new reverse lamps below the bumper, then painted the lamps in the original reverse lights amber and wired them up as indicators doing away with the combined brake light/indicator so they are now only break lights. Its a requirement for Western Australia that the Brake light and indicator cannot be the same bulb. So that was my solution, all a bit silly in my opinion but that's the law here if you want it registered and insured on the road.

Cheers
 
New wiring of the 6 wires coming from the steering column

I have a new wiring system I want to install on my 1953 Buick Special and have just found out that since I have 6 wires coming from the steering column (original) instead of 8 it will not work.
It will not allow the turn signals to work properly?

anyone have any input or suggestions?

Thanks,
 
rpmbo said:
since I have 6 wires coming from the steering column (original) instead of 8 it will not work.
It will not allow the turn signals to work properly?
Click to expand...

A stock 53 uses separate bulbs for turn signals and brake lights. The turn signal switch has fewer wires because the brake light circuit doesn't have to go through it. Just connect your brake light switch directly to the brake light bulbs instead of to the TS switch, Your turn signals and brake lights should both work fine.

Ray
 
53 buick special steering column wires

raycow said:
A stock 53 uses separate bulbs for turn signals and brake lights. The turn signal switch has fewer wires because the brake light circuit doesn't have to go through it. Just connect your brake light switch directly to the brake light bulbs instead of to the TS switch, Your turn signals and brake lights should both work fine.

Ray
Click to expand...

Thanks Ray and that makes sense.. that is what I will do.
Can you tell me about the two commons coming from the column are for? of the six wires two are marked LH and two are marked RH and the other two are marked C.

I am thinking one of the commons is or the horn. Curious about what the other one is for? any ideas

Thanks again for the input

Bob
 
It took me a while to figure out what you meant by "two commons" because I couldn't find a 53 wiring diagram.

I ended up looking into my own car which is a 52, and which I HOPE is wired the same way as yours. These cars (or at least mine) have a turn signal flasher with 3 terminals marked X, L and P.
X is power in from the ignition switch
L and P both go to the TS switch. L supplies power for the regular turn signal bulbs and P supplies power for the dash indicators only. These are probably the two commons you are asking about.

The TS switch has 6 terminals. They are not numbered on mine, but I am calling them 1 through 6 just for identification purposes.
1. Power in from flasher L terminal
2. Power in from flasher P terminal
3. Power to both LH turn signals (F&R)
4. Power to both RH turn signals
5. Power to LH dash indicator
6. Power to RH dash indicator

Now are you are you asking about this because you are using an aftermarket wiring harness and it has a 2 terminal flasher? If yes, this should not cause a problem. Just connect the two commons together and feed that junction from the flasher.

Before doing this though, it might be best to check continuity through the switch with a multimeter or test lamp. In other words, try one common in all 3 switch positions and see which pair of L&R wires it connects with. The other common should connect with the other pair of L&R wires. The only bad thing is that you won't be able to determine for certain which L&R pair is for the turn signals and which pair is for the dash indicators. If one pair of wires is heavier than the other, use that pair for the turn signals and you should be ok. If all 4 wires are the same gauge, either flip a coin or try to find a diagram so you can go by color.

If you are still having problems with the turn signals after trying this hookup, post again and I will try to help get it sorted. Good luck, and please let us know how everything works out, either good or bad.

Ray
 
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