12v Starter Solenoid in a 6v car.

[OUTFXD]

Title says it all.

 

Jacquiline has had starting issues since I got her.

 

I tried replacing the solenoid with a cheap amazon one. It was Chinese with metric threads.  the old Solenoid would at least turn the engine, the new one just clicked so I dismissed it as defective. I have had the starter professionally rebuilt. I replaced the battery cables with 1/0 gauge battery cables. I added extra ground straps at the battery and the Starter. 

 

With a fully charged 6v or  8v battery the engine barely turns over.  With a 12v battery the starter runs like a 6v starter with 12v running through it and the engine fires up in seconds.

 

The only thing that makes sense to me is that somebody just replaced the solenoid with a generic solenoid and accidentally  installed a 12v solenoid.  One that wouldnt respond to 6 or even 8 volts.

 

Having virtually zero experience with 6v systems I have to ask,  Does this make sense? Wouldnt a 12v solenoid just NOT do anything with 6 volts?

 

Suggestions, advice, and insight welcome!

[Loren]

A solenoid is nothing more than an electrical switch. It does nothing magical to the electricity.

The signal wire goes to a coil which when energized becomes a magnet drawing two contacts together.

The contacts connect the battery to the starter with a very low current drop.

On a 6 volt car the cables have to be very heavy because the low voltage takes a lot of amps to turn the engine over.

You will note how small 110 volt cords are by comparison.

A 12 volt solenoid won’t last long in a 6 volt system because the coil will see an under volt condition and won’t pull the contacts together efficiently.

A 6 volt solenoid in a 12 volt system won’t last long because the coil will overheat from excessive voltage.

So if you question the voltage or the functioning of a solenoid it’s easy to check.

A “real time” check involves two volt meters, one at the battery and a second one at the load.

Trigger the starter and see how much the voltage drops.

If they both drop the same and it’s a lot, you may need a battery (or a better ground cable connection)

If the load side drops more then you have to isolate wether it is a cable or the solenoid by working your way back from the starter.

The cable from starter to the solenoid. The solenoid or the cable to the battery.

 

A safety note: Never allow any kind of sparks near a battery! Don’t connect wires that can make a spark (loads will make a spark). If you have to jump a battery connect the last cable at the engine block. Batteries give off hydrogen gas which is explosive. Try and cover the battery with a fender cover and don’t lay tools on it.

A bad connection inside the battery has blown up many of them in my experience. Some brands are notorious for this.

[OUTFXD]

14 minutes ago, Loren said:

A 12 volt solenoid won’t last long in a 6 volt system because the coil will see an under volt condition and won’t pull the contacts together efficiently.

 

In this example. Would the contacts simply fail to function(No contact), Or have a "Poor connection"? Potentially Worsening the efficiency of the contacts by tacking them up?

 

I Will test out a Real time Check in the next couple days.

 

Thank you for all the input!

[Loren]

If the contacts aren't pulled together swiftly and tightly they will burn. That becomes a downward spiral.

When contacts start to burn the resistance goes up and they burn more.

Good solenoids have an almost violent action. They snap closed like a rat trap. lol

[squirebill]

So from high school Physics (in the mid-60s of the last century) when studying "Electricity and Magnetism" there was something about a "right hand rule".  Had to do with wrapping the fingers of your right hand around the coil with the pinky towards the positive end of the coil ....then the magnetized core in the center of the coil would move in the direction of your right hand thumb.  This is all a little fuzzy at this point, but that was the jist of it.  Anyhow, I wonder if the polarity of our electrics being Positive + ground makes a difference as far as solenoids are concerned. Regards.

[Kilgore47]

Had he same problems with the 47 P15 when I got it.  Turned over slow.  First thing I did was go through the starter.  That didn't help.  Then I re wired the car with a standard 6 volt wiring harness.  Didn't fix it.  Then I replaced the battery cables with 00.  Still turned over slow.  I finally got an expensive 6 volt battery with 1000 cold cranking amps and now it starts good.  The 6 volt lead acid battery I bought when I got the car may have been weak off the shelf because that should have worked.  

[Rick Michalik]

1/0 cable seems small.  Would recommend 3/0 in addition to the other items mentioned. 
-Rick

[desoto1939]

1 hour ago, Rick Michalik said:

1/0 cable seems small.  Would recommend 3/0 in addition to the other items mentioned. 
-Rick

Rick:

The previous post was refering to either 1 gage or zero gage size thickness to 1/0.  Also the 3 gage is nat as big as the 1 or zero gage.  According to my Mopar Bulletins they refer to either 1 or 0 gage as the proper gage of battery cable to use on the old 6 volt positive grounded cars and trucks.

 

Rich Hartung

Desoto1939@aol.com

[Rick Michalik]

3/0 refers to 000 cable.  The area of 000 cable is 85 square mm.  1/0 or 0 cable is 53.5 square mm.  I would recommend 3/0 cable.  What’s on there now is too small for 6v I’m my experience. 

[Sam Buchanan]

12 minutes ago, Rick Michalik said:

3/0 refers to 000 cable.  The area of 000 cable is 85 square mm.  1/0 or 0 cable is 53.5 square mm.  I would recommend 3/0 cable.  What’s on there now is too small for 6v I’m my experience. 

 

1/0 is what I and many in the group have installed and they work great in my car.

 

[desoto1939]

15 minutes ago, Rick Michalik said:

3/0 refers to 000 cable.  The area of 000 cable is 85 square mm.  1/0 or 0 cable is 53.5 square mm.  I would recommend 3/0 cable.  What’s on there now is too small for 6v I’m my experience. 

Here is a page taken from My MoPar cables terminal and wire bulliten on Battery Cable stating to use 1 gage battery cable.

 

[Los_Control]

I always did think the wiring labeling system was a bit screwy. The smaller the number the larger the wire.

But it is true with all automotive wire, 16 gauge is like small speaker wire & 10 Gauge is heavy duty lights or charging wire.

Same with battery cables. 1/0 as said above, 0/0 wire used for welding clamps is even better. I have 2/0 on my battery as it is what was available. I think it is a bit small but works well so far.

Even household wiring is the same. The smaller the number the larger the wire.

 

[Rick Michalik]

I am not disputing the manual or anyone. Simple fact is bigger cable is less resistance for current resulting in more battery power available to the starter. 
 

sorry I chimed in

[Sam Buchanan]

38 minutes ago, Rick Michalik said:

I am not disputing the manual or anyone. Simple fact is bigger cable is less resistance for current resulting in more battery power available to the starter. 
 

sorry I chimed in

 

Apology not necessary. It's true larger cables have less resistance, but practicality and diminishing returns are also under consideration when deciding if a set of cables is large enough for reliable starting. Mopar engineers and seventy+ years of field history have demonstrated that 1/0 cable is very adequate at a reasonable cost and availability provided the battery, grounds and starter are in good condition. 3/0 cable is HUGE, nearly 3/4" in diameter and probably perfect for starting tractors and diesel trucks in cold weather.   ?

Edited February 5, 2022 by Sam Buchanan

[keithb7]

000 cable is monstrous. Won't hurt anything though, except your bank account. 2/0 is my go-to for 6V,

yet for the old girls with the battery under the driver's seat, it can be a little challenging to fit in there. The big

fattie wire tends to rub in the confined areas around the battery box under the seat. If the negative rubs though, it's 

going to get very interesting very fast. A moment you'll never forget.

 

Edited February 5, 2022 by keithb7

[Sniper]

Doesn't really matter how fat your battery cable is if the studs on the starter and solenoid are smaller.  Smallest link in the chain is what will determine current flow.  Nice thing is, though with Keith's chart that shows continuous carrying capacity, you can overload the cable for short periods of time.

[chrysler1941]

Just one question. Are you able to turn the professionally rebuilt starter with two fingers? 

[OUTFXD]

Dont think I tried that after it came back.  I seem to remember it being stiffer than I thought it would be.

[Sniper]

Don;t forget a 12v solenoid run in a 6v application is going to have twice as much current running thru it as it was designed to handle.

[OUTFXD]

Finally caught a buddy before he went to work and got him to hold the start button as I took voltage readings (In short bursts of course).   with a charged 8v battery I got 8.4 at the battery.  8.37 at the battery side of the solenoid and 3.34 at the starter side of the solenoid. 

 

I stopped there. Checked with the local parts hause and they have a generic 3 wire 6v starter solenoid in stock.

 

I am trying to decide if I should sit down and figure out how much money I threw at the starter circuit trying to figure the problem out. Or if I am better off just not knowing that number.

[Los_Control]

Well, if you do figure out the number. Just add it to the line containing money spent on education 

 

[keithb7]

Better off not knowing. The lesson has been learned. No point throwing salt in the wound. I stopped keeping track of my hobby expenses. Rips the fun right out of a hobby. 

Edited February 5, 2022 by keithb7

[1950 Special Deluxe]

2 hours ago, Los_Control said:

Well, if you do figure out the number. Just add it to the line containing money spent on education 

 

I have always been told Education is expensive. 

[Rick Michalik]

Agreed.  Never count the receipts!

[squirebill]

So the input to the solenoid coil is the little terminal on the solenoid.  The solenoid coil circuit is completed through the housing of the solenoid to the body of the vehicle. Do you have a good clean electrical connection between the solenoid and the body of the car?  Just for testing, maybe try a jumper wire from under one of the mounting screws directly over to the ground terminal on the battery. Not saying this will correct the situation of a 12VDC solenoid in a 6VDC circuit but maybe you would get less voltage drop across the large terminals.