12-Volt to 6-Volt Voltage Reducer

[MarkB2PW]

Has anyone used this 12v to 6v reducer before?


I did a 12v to 6V conversion on my car and put this in for the horn, fuel and temp gauges.
I'm sending 12v to it from the ignition switch and I get 6 volts out of the reducer. But it's not enough to power my horn, temp or fuel gauge even at 20 amps.
I can take my old 6v battery and run power direct to the horn and it works, but not with the 6v from the reducer. Any experience with this would help.

[Spinneyhill]

Have you set it up as per the fifth bullet point?

[maok]

It should work for the fuel and temp gauge but may not for the horn due to the horn drawing a large spike/surge of amps.

 

[Bloo]

The surge current of the horn is probably way too high. They are pretty much a dead short until the diaphragm starts to move. You probably need to use a resistor instead for the horn. I might try a Chrysler ballast resistor, and see if the horn sounds about right.

 

Leave plenty of room around the resistor. It is gonna get hot when in use. That shouldn't be much, but you must plan for the day the horn sticks and the resistor gets really hot.

[vermontboy]

Not certain that it makes a difference but did you change the polarity ?

[Frank DuVal]

The 12 volt battery should smooth out the DC going into the converter as noted in the 5th bullet. A typical 12 volt car battery is a Farad or so.

 

Can you put a 6 volt battery in there for this to charge, then the horn will work. Or a large "compute*r" capacitor of several thousand microfarads.

 

*That's what we called them back in the 7os when they were a new item in the electronics industry. Now it is just a large electrolytic capacitor.

[Rusty_OToole]

Why not just take a center tap off the battery?

[MarkB2PW]

2 hours ago, Spinneyhill said:

Have you set it up as per the fifth bullet point?

I assumed that the 12v battery was a stable 12v supply.  I'm not an electronics guy so I would not know the difference.

2 hours ago, vermontboy said:

Not certain that it makes a difference but did you change the polarity ?

It was always a positive ground.  1950 Olds 88.

2 hours ago, Frank DuVal said:

The 12 volt battery should smooth out the DC going into the converter as noted in the 5th bullet. A typical 12 volt car battery is a Farad or so.

 

Can you put a 6 volt battery in there for this to charge, then the horn will work. Or a large "compute*r" capacitor of several thousand microfarads.

 

*That's what we called them back in the 7os when they were a new item in the electronics industry. Now it is just a large electrolytic capacitor.

Frank, are you suggesting that I keep a six volt battery in the car also, and just use the reducer to charge the 6v battery.  Then using the 6v battery for the horn and gauges. There's plenty of room in the trunk for a second battery.

The horn does work on 12v, it just sounds unusual.

BTW, the voltage into the fuel gauge is 6 volts from the reducer.  The voltage out of the fuel gauge is 3 volts.  Is that normal or is the gauge bad?

Thanks for the help.

 

 

[Frank DuVal]

Yes to a small 6 volt battery for that purpose.

 

If the gauge voltage is read with the sender in circuit, then yes, that would be normal, as the sending unit and gauge act as a voltage divider circuit (if it is like most GM cars I have worked on). The voltage should change with tank level.

[pont35cpe]

I`ve used 12v on 6v horns for years/decades never had a problem(no burn out). They are louder and do get peoples attention..

[Rusty_OToole]

If you have 2 horns you could wire them in series, then they will get 6v each off a 12v wire.

[PFitz]

This may seem like a silly question, but why not put the system back to 6 volts the way it worked originally ?

 

Where are you safely going to put a 6 volt battery with enough amperage output to work a 6 volt horn, and how are you going to keep it charged  ?

 

Maybe it's just me, but it seems that very often changing 6 volt systems to 12 volts causes more problems and complexity then it solves.,.... when putting all that effort and money into properly repairing the original 6 volt system would solve all the problems. 

 

Paul

[Bloo]

True enough, but I always try to help if I have any ideas. I have yet to see a 12v conversion with every last thing working. These DC-DC converters commonly available are a tool we never had back in the day. When resistors were used for everything, the resistor had to use as much power as the accessory did. It will be interesting to see how well DC-DC converters solve the problems. I am a bit skeptical because pre-computer automotive electrical systems are extremely dirty, often with spikes over 200 volts on a 12 volt car. Car batteries make horrible filter capacitors, and they are even worse if the connections are bad. I wonder if the DC-DC converters will be able to deal with the dirty electrical systems. Time will tell.

 

I still think a resistor is the best solution for running a 6 volt horn on 12 volts. The back EMF from something like a horn is probably going to blow that converter to smithereens.

 

As for the gauges, the converter might work just fine.

Edited April 5, 2019 by Bloo (see edit history)

[MarkB2PW]

I appreciate all your input  and I think I'll be able to resolve the issues using just the 12-volt for the horn and 6 volt reducer for the fuel gauge

 

Looks like I got bigger problems though I'm sitting on the street waiting for AAA to come get the car... I'm pretty sure I got carburetor issues.

I'll keep in touch

 

[MarkB2PW]

 I think I'm going to look I think I'm going to look for an alternative to this Rochester side draft two-barrel carburetor

 

[Hans1]

I must be missing something, the spec's are confusing:

6 VDC at 20 A  and 120W

a 20 amp circuit should put out 1500 w  easily.

Perhaps it's only  2.0 amp.

Also the instructions indicate the need for a Cap on a variable input from a pulsed generator.

They may mean Alternator, but if using an old generator, the batt may not provide a stable reference source with the generator in operation.

It may not handle ripple well.

 

I do not know physical size of unit but in the old days I think we used a 1000 watt wire wound ceramic screw tap  resistor to drop 12 to 6.  

Sure got hot, had to mount it away from any thing!

[C Carl]

Great use of "down time", Mark' ! Hanging out with your friends here ! I hope this picture helps, since so many of us "been there, done that". I hope you're back cruising soon.    -   Carl 

 

 

[Frank DuVal]

1 hour ago, Hans1 said:

6 VDC at 20 A  and 120W

a 20 amp circuit should put out 1500 w  easily.

 

Ohms Law!

 

E=IR

 

and W=EI

 

So, 6 volts x 20 amps is 120 watts!

 

You have 120 volts on the mind.....😉

 

[Frank DuVal]

1 hour ago, MarkB2PW said:

I'm pretty sure I got carburetor issues

 

What's that old saying? 90% of carburetor troubles are ignition....😉

 

Also, what Rochester side draft carburetors? I can only find reference to Rochester R and RC, which were on the 1962/ or so Jetfire.

 

Besides electrical changes, what engine changes have been done to the car?🙄

 

Most all Rochester carburetors are easy to rebuild, or to find someone rebuild them. Work great in original form.

[Hans1]

Oh! thank you Frank !

Perhaps that's why I like cars in the 20's and 30's 

I need to think longer before................

again Thank you

 

 

[Grimy]

Mark, the carb on that Olds is not side draft--the air horn is at 90 degrees to facilitate use of an oil bath air cleaner, just like Packard 12s.  You may need to put a kit in yours, but mine of years ago (in a 1949 98) was very reliable and trouble-free.

[carbking]

On 4/7/2019 at 12:36 AM, Grimy said:

Mark, the carb on that Olds is not side draft--the air horn is at 90 degrees to facilitate use of an oil bath air cleaner, just like Packard 12s.  You may need to put a kit in yours, but mine of years ago (in a 1949 98) was very reliable and trouble-free.

 

The carburetor, as stated by grimy, is not a side-draft. "Draft" in a carburetor designation refers to the direction the air/fuel is going when it leaves the carburetor. A side-draft carb would have the air/fuel moving relatively horizontally when leaving the carburetor. Updraft, downdraft, and sidedraft are the three common types; however, I wouldn't be surprised if Marvel didn't have one that went anti-goglin (hillybillyese  for oblique) just to foul up the normal convention.

 

The AA Rochester used on the 1949 and 1950 Olds has two diaphragms; one is the accelerator pump, the other the actuating valve for the power/economizer valve. We spent a small fortune some 35 years ago reproducing the accelerator pump to put in kits (still have not retrieved that investment), but could not economically (even as economically as the pump) do the casting and diaphragm for the actuating valve. However, one may carefully disassembly this piece and install a new diaphragm. It isn't plug and play, it requires machine work but it may be done.

 

A much better (opinion) option is to replace the AA with the optional Carter that was used in 1949 and 1950. The major issue with the Carter is the aircleaner required an adapter as the air intake on the Carter is oval. Much better (opinion) design on the Carter, and it uses readily available parts, with a leather (impervious to ethanol) accelerator pump.

 

 

 

Jon.

Edited April 8, 2019 by carbking (see edit history)

[MarkB2PW]

16 hours ago, carbking said:

 

The carburetor, as stated by grimy, is not a side-draft. "Draft" in a carburetor designation refers to the direction the air/fuel is going when it leaves the carburetor. A side-draft carb would have the air/fuel moving relatively horizontally when leaving the carburetor. Updraft, downdraft, and sidedraft are the three common types; however, I wouldn't be surprised if Marvel didn't have one that went anti-goglin (hillybillyese  for oblique) just to foul up the normal convention.

 

The AA Rochester used on the 1949 and 1950 Olds has two diaphragms; one is the accelerator pump, the other the actuating valve for the power/economizer valve. We spent a small fortune some 35 years ago reproducing the accelerator pump to put in kits (still have not retrieved that investment), but could not economically (even as economically as the pump) do the casting and diaphragm for the actuating valve. However, one may carefully disassembly this piece and install a new diaphragm. It isn't plug and play, it requires machine work but it may be done.

 

A much better (opinion) option is to replace the AA with the optional Carter that was used in 1949 and 1950. The major issue with the Carter is the aircleaner required an adapter as the air intake on the Carter is oval. Much better (opinion) design on the Carter, and it uses readily available parts, with a leather (impervious to ethanol) accelerator pump.

 

Jon.

 

It is a Rochester AA.  I bought a kit and rebuilt it.  I sent the economizer valve back to a shop in Florida to replace the diaphragm.

I would like to try a different carburetor to see if the performance changes.  What model Carter is that?  And where is the best place fro me to get one?  Or is there a modern alternative that would work better?  I appreciate you sharing your knowledge.

I like the comment from Frank, "What's that old saying? 90% of carburetor troubles are ignition...." .  I'm not sure the problem is the carburetor, but would like to eliminate it from the equation. 

After I changed to 12v it did run better.

I also replaced the fuel pump with a rebuilt 2 weeks ago, but, when it died on Saturday it felt like it was running out of gas.  I could get it to start and run by revving it, but it would not stay running. 

[carbking]

3 hours ago, MarkB2PW said:

 

It is a Rochester AA.  I bought a kit and rebuilt it.  I sent the economizer valve back to a shop in Florida to replace the diaphragm.

I would like to try a different carburetor to see if the performance changes.  What model Carter is that?  And where is the best place fro me to get one?  Or is there a modern alternative that would work better?  I appreciate you sharing your knowledge.

I like the comment from Frank, "What's that old saying? 90% of carburetor troubles are ignition...." .  I'm not sure the problem is the carburetor, but would like to eliminate it from the equation. 

After I changed to 12v it did run better.

I also replaced the fuel pump with a rebuilt 2 weeks ago, but, when it died on Saturday it felt like it was running out of gas.  I could get it to start and run by revving it, but it would not stay running. 

 

 

"  I'm not sure the problem is the carburetor, but would like to eliminate it from the equation. "

 

The carburetor is the very LAST item to eliminate from the equation!

 

ONE TEST IS WORTH 1000 OPINIONS!

 

In order:

 

(1) compression test WHY because if the compression is bad working on ignition or carburetion is a waste of time and money

(2) ignition test WHY because if the ignition is faulty, nothing you do to the fuel system will help

(3) fuel delivery system test WHY because if there is no fuel in the carburetor, the carburetor doesn't work

(4) carburetion test

 

In (2) above, if points and condenser have been replaced with some electronic gismo, restore the points and condenser for the test. The electronics simply adds another degree of unknown. If you are in love with electronics, and there is no change, by all means put it back. If you do have an electronic gismo for the distributor, and have not upgraded to any alternator - DO SO!

 

As to the Rochester AA:

 

Rochester began producing "carburetors" in 1949 with the AA used only by Oldsmobile. This carburetor was continued with a minor calibration change in 1950, and then thankfully discontinued. In 1951, Rochester produced the type BB which lasted, again thankfully, for one year only; and Rochester quit trying to make two-barrel carbs  for a time. In 1955, Rochester tried another two-barrel, the Power-Jet. Again, one year only. In 1956, Rochester began production of the 2G series (they had been making the 4G four-barrel), which turned out (opinion) to be one of the finest 2-barrel carbs ever made. Variants of the 2G were still being used by new cars in the 1980's.

 

As to other options:

 

In 1949 and 1950, Oldsmobile also used a Carter type WGD identification 714s. In 1950, the 714s was tweaked into the 849s. Both are conventional Carter WGD carbs, but with the laid-over airhorn necessary for the 1949 and 1950 Olds. Both Carters required an oval adapter to adapt to the Rochester air cleaner.

 

Personal and professional opinion - if I owned a 1949 or 1950 Oldsmobile driver OR showcar, it would have the Carter correct for the year.

 

Should you decide to made the switch, there is a grumpy old hillbilly in Missouri that can probably supply either of the Carters.

 

EDIT: I just reread the thread, and see you have electronic gismos plus a 12-volt conversion. I am pretty sure that grumpy old hillbilly just sold the last of his Carters. Good luck.

 

Jon.

 

Edited April 8, 2019 by carbking (see edit history)

[Rusty_OToole]

On 4/5/2019 at 8:31 AM, PFitz said:

This may seem like a silly question, but why not put the system back to 6 volts the way it worked originally ?

 

Where are you safely going to put a 6 volt battery with enough amperage output to work a 6 volt horn, and how are you going to keep it charged  ?

 

Maybe it's just me, but it seems that very often changing 6 volt systems to 12 volts causes more problems and complexity then it solves.,.... when putting all that effort and money into properly repairing the original 6 volt system would solve all the problems. 

 

Paul

Doesn't seem silly to me. On these boards when someone comes along with a 6V problem, if they fix the problem and keep it 6V that is the end, we don't hear any more about it. If they decide the solution is to convert to 12V they keep coming back and coming back with problem after problem until they either fix whatever was wrong in the first place, or sell the car in despair.

[MarkB2PW]

3 hours ago, carbking said:

 

 

"  I'm not sure the problem is the carburetor, but would like to eliminate it from the equation. "

 

The carburetor is the very LAST item to eliminate from the equation!

 

ONE TEST IS WORTH 1000 OPINIONS!

 

In order:

 

(1) compression test WHY because if the compression is bad working on ignition or carburetion is a waste of time and money

(2) ignition test WHY because if the ignition is faulty, nothing you do to the fuel system will help

(3) fuel delivery system test WHY because if there is no fuel in the carburetor, the carburetor doesn't work

(4) carburetion test

 

In (2) above, if points and condenser have been replaced with some electronic gismo, restore the points and condenser for the test. The electronics simply adds another degree of unknown. If you are in love with electronics, and there is no change, by all means put it back. If you do have an electronic gismo for the distributor, and have not upgraded to any alternator - DO SO!

 

As to the Rochester AA:

 

Rochester began producing "carburetors" in 1949 with the AA used only by Oldsmobile. This carburetor was continued with a minor calibration change in 1950, and then thankfully discontinued. In 1951, Rochester produced the type BB which lasted, again thankfully, for one year only; and Rochester quit trying to make two-barrel carbs  for a time. In 1955, Rochester tried another two-barrel, the Power-Jet. Again, one year only. In 1956, Rochester began production of the 2G series (they had been making the 4G four-barrel), which turned out (opinion) to be one of the finest 2-barrel carbs ever made. Variants of the 2G were still being used by new cars in the 1980's.

 

As to other options:

 

In 1949 and 1950, Oldsmobile also used a Carter type WGD identification 714s. In 1950, the 714s was tweaked into the 849s. Both are conventional Carter WGD carbs, but with the laid-over airhorn necessary for the 1949 and 1950 Olds. Both Carters required an oval adapter to adapt to the Rochester air cleaner.

 

Personal and professional opinion - if I owned a 1949 or 1950 Oldsmobile driver OR showcar, it would have the Carter correct for the year.

 

Should you decide to made the switch, there is a grumpy old hillbilly in Missouri that can probably supply either of the Carters.

 

EDIT: I just reread the thread, and see you have electronic gismos plus a 12-volt conversion. I am pretty sure that grumpy old hillbilly just sold the last of his Carters. Good luck.

 

Jon.

 

 

I just did a compression test the results look like this:

Cylinder      

1  83

2  87

3  80

4  83

5  80

6  84

7  83

8  85

 

I can get it to run, but, when I shut the car off fuel runs out the air horn. Why?

 

[Frank DuVal]

All plugs out and the throttle held wide open?

[MarkB2PW]

No.  I pulled the plugs one a time and cranked it for each one.  Was that wrong? 

And would that change the compression numbers I was getting?

Edited April 8, 2019 by MarkB2PW
Adding a question (see edit history)

[Roger Frazee]

I may be wrong, but it looks like your 12 to 6 volt reducer is changing 12 volts DC to 12 volts AC, and then cutting of one half of the AC wave with a single diode.  If my theory is correct, the 6 volt output would be a pulsating DC if not filtered internally.  This is why they recommend a capacitor on the output.  I'm with Frank that you should use the reducer to charge a 6 volt battery and run your 6 volt devices off of the battery.

[Bloo]

Compression testing is normally done with the plugs because all that cranking is hard on the starter, and it tends to run the battery down, changing the cranking speed before you get done. Numbers would probably be lower bacause of the lower cranking speed.

 

That said, don't get too hung up on absolute numbers. People tend to see a number in a book and chase their tail because the numbers don't match. No two competent mechanics, or two different gauges will ever come up with the same results. In real life, what matters is that the numbers are even. A pattern showing evenness or big differences between cylinders will show up in any properly done test. Most textbooks will say less than 10%. In real life 20% is common in cars that run perfectly.

 

Your numbers do sound a wee bit low to me, but the evenness indicates no burned valves. That is good. They may have been a little lower than expected because of slow cranking (testing with the plugs in).

 

It may pay to check that your camshaft timing has not jumped. If you have not moved the distributor since it ran good (I hope), you might be able to just crank the engine (with a wrench, with the plugs out), until the rotor is almost to the plug wire that goes to cylinder #1. Then, crank slowly with the wrench until the points just open. This should be just before top dead center on your timing marks.

 

The reason it works is that the distributor is driven by the camshaft, and if the cam timing is wrong, it screws up the ignition timing too. As long as nothing had been moved since it ran right, looking at the ignition can tell you. If the distributor has been moved, disregard this method.

Edited April 9, 2019 by Bloo (see edit history)

[MarkB2PW]

Thanks Bloo it gives me hope.

[Bloo]

I would like to know exactly what you mean by "air horn", but if the carburetor is literally running over with fuel, there is a problem with the float system. I wish I was sure exactly what you mean.

 

The float in a carburetor works exactly like a toilet. A valve allows liquid in until the float, floating on top of the liquid, shuts the valve. The big difference is that in a carburetor the exact level is critical.

 

Stuff that causes carburetors to run over:

 

1) Fuel pressure too high. This often happens when people install electric fuel pumps. If the pressure is way too high, it can just blow past the float valve and run over. If the pressure is a little wrong, it can change the float level, leading to a whole bunch of tail chasing because the height setting in the book assumed the original fuel pressure.

 

2) Float valve shot. This one is self explanatory. The fuel cant shut completely off, and it just runs all the time (like a malfunctioning toilet).

 

3) Bad float. Any holes in the float, or any liquid inside changes the buoyancy and reduces the float's ability to shut the liquid off. Since the float level in a carburetor is critical, there is no room for error. The float must have no leaks, period.

 

4) Float level set wrong. The service manual will show how to set it and what the level measurement is.

 

Hope that helps. I may be completely out to lunch if I misunderstood where the gas is coming from.

Edited April 9, 2019 by Bloo (see edit history)

[MarkB2PW]

1) Fuel pressure too high. This often happens when people install electric fuel pumps. If the pressure is way too high, it can just blow past the float valve and run over. If the pressure is a little wrong, it can change the float level, leading to a whole bunch of tail chasing because the height setting in the book assumed the original fuel pressure.

Response:  I put a rebuilt fuel pump(mechanical) from Fusick on less than 10 miles ago.

 

2) Float valve shot. This one is self explanatory. The fuel cant shut completely off, and it just runs all the time (like a malfunctioning toilet).

Response:  I rebuilt the carburetor myself less than 20 miles ago.  Not to say I didn't miss something.

 

3) Bad float. Any holes in the float, or any liquid inside changes the buoyancy and reduces the float's ability to shut the liquid off. Since the float level in a carburetor is critical, there is no room for error. The float must have no leaks, period.

Response:  I rebuilt the carburetor myself less than 20 miles ago.  Not to say I didn't miss something.

 

4) Float level set wrong. The service manual will show how to set it and what the level measurement is.

Response: When I rebuilt the carb I was very meticulous about getting this set right, 23/32" I believe.

 

Fuel coming out of the side air filter hole dumping onto the coil.  Something is bad.  I'll remove it tomorrow maybe.

 

[Bloo]

Some quick thoughts....

 

1) Do I see two fuel inlet line fittings on the lid? If so, what do they go to?

 

2) Dunk your float in hot (or nearly boiling) water and look for a stream of bubbles to the surface of the water.

 

3) What seals the float valve itself to the lid of the carb? Does it screw in? Is there an o-ring or gasket or something? What keeps the fuel from leaking around the outside of the float valve where it attaches to the lid?

Edited April 9, 2019 by Bloo (see edit history)

[Frank DuVal]

1 hour ago, MarkB2PW said:

I put a rebuilt fuel pump(mechanical) from Fusick on less than 10 miles ago.

 

If it was a Corvair fuel pump, then this is the problem. I do not know why, but it seems all the new made Corvair mechanical fuel pumps have springs that put out 5 to 7 psi! So, we buy new pumps, take them apart and put in the old springs, back to less than 5 or so psi......

 

Maybe these pumps have the same issue? Call Mike Fusick and see if others have complained.

 

Got enough fittings and a gauge to get a pressure reading?

[JACK M]

I remember an instructor at a marine training class tell us that if the lowest compression is within 15% of the highest then it is OK.

Yours is at about 9%.

Obviously you are on the right track with a fuel issue if there is a leak.

Kind of got to a different subject here, but I hate a breakdown.

 

As for the electrical I agree with the idea of adding a six volt battery.

This new fangled electrical stuff will be a great help with those that do 6 to 12 conversions. You might be able to use something as simple as NiCads or similar rechargeable flashlight batteries  to run the six volt gauges. I suspect that you will have to switch this circuit so the gauges don't run when you are parked.