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Joined: Sep 2014
Posts: 15
Grease Monkey
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OP
Grease Monkey
Joined: Sep 2014
Posts: 15 |
This is going to take some explaining so please bare with me
1938 Master deluxe, stock 6 volt system with an added 12V booster battery to aid in starting. Relay connected so that an isolated momentary switch to a relay connects positive to top of starter motor = 12 v Grounded to frame. Some have said to ground positive to frame and reverse wiring but the relay only buzzes - BUT- that is not the problem as it works great when the 6 volt is weak.
As the 12V was already in the car I decided to put in a 12V radio from Retrosound = hooked it all up and works fine - some interference from car but I dont have an external radio antenna and that doesnt help THE PROBLEM is it works fine when the car is not going but when running and drops to idle the generator starts taking power from the batteries and the radio cuts in and out - soon as you increase the RPM it stops.
HOW does the voltage regulator and generator draw power from the 12 volt? there are a couple of older wires on one regular so maybe it was set up as a partial trickle charger while running? OR - is it the common ground.
Every possible tried - isolated the unit so no ground other than the battery .
Wonder if I disconnect the postive from a relay to the starter motor and both batteries on the same post it would stop drain on 12 V
I trickle charge the 12V all the time so it can be completely separate
Help
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Joined: Sep 2012
Posts: 300
Backyard Mechanic
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Backyard Mechanic
Joined: Sep 2012
Posts: 300 |
Hey DRB ....since no one has replied I`ll jump in to say hello at least!....my only thought is yes, it sounds like a nightmare and if it were mine I`d ditch the 12 stuff and go straight 6 volt and get it to run as it was designed to do . Not trying to be negative at all , but it just sounds like a quagmire that is not necessary....good luck with it though ....keep us posted on your findings
David Martin-Hendersonville NC, Pine Island Fl....... 1940 Chevy SDSS,
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
I drove my '39 for 40 years and 40,000 miles with the 6 volt with no problems. 
Gene Schneider
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Joined: Dec 2011
Posts: 1,019 Likes: 3
ChatMaster - 1,000
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ChatMaster - 1,000
Joined: Dec 2011
Posts: 1,019 Likes: 3 |
Hello DRB,
I'm not sure how to answer this. but the addition of a 12 volt battery is masking a problem that might be easy to fix.
A weak battery may be nothing more than the wrong size battery cables. A 6 volt system requires 00 gauge or 1 gauge wire for the positive and a large braided cable for the ground (if you are having the car judged). A 00 gauge or 1 gauge wire will work for the ground also.
I have seen this first hand on a '36 Chevy pick-up at a cruise night. Gentleman's starter was turning the engine slow like a low battery. I offered to jump start him and when I went to attach the cables I noticed the battery cables were a small diameter. They were for a 12 volt battery. I suggested he change them which he did and now the truck starts easily every time.
As for a 12 volt radio, it might be easier to install a voltage booster to power it. I don't know if this will stop the interference but it should simplify the wiring. I installed one in my '37 MD for charging my phone or my GPS. I have it wired into the lighter receptacle. (bought mine from CoF's)
My '37 MD has a cut-out switch, I think the '38's have a regulator. I would disconnect the 12 volt system and check the 6 volt system to be sure it is working properly first.
Keeping everything simple usually works best.
Dave
old cars are meant to be driven !!
VCCA # 047832
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Joined: Feb 2008
Posts: 3,801 Likes: 1
ChatMaster - 3,000
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ChatMaster - 3,000
Joined: Feb 2008
Posts: 3,801 Likes: 1 |
Hey DRB ....since no one has replied I`ll jump in to say hello at least!....my only thought is yes, it sounds like a nightmare and if it were mine I`d ditch the 12 stuff and go straight 6 volt and get it to run as it was designed to do . Not trying to be negative at all , but it just sounds like a quagmire that is not necessary....good luck with it though ....keep us posted on your findings Yes, all the 12 volt stuff is not needed, if the 6 volt system is in tip top condition. A good battery, starter and HEAVY GAUGE battery cables, as mentioned, will keep that 6 volt system humming along, on its own.
1951 Chevy Styleline Deluxe 2 door sedan / purchased from second owner 6-19-2000.
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Joined: Aug 2014
Posts: 327
Backyard Mechanic
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Backyard Mechanic
Joined: Aug 2014
Posts: 327 |
..... Relay connected so that an isolated momentary switch to a relay connects positive to top of starter motor = 12 v Grounded to frame. Can you elaborate a little more on this? I would surmise that your momentary switch connects the 12V terminal to the starter ONLY when you try to start the car, correct? Is anything else connected to the 12V battery's positive terminal at all times? HOW does the voltage regulator and generator draw power from the 12 volt? there are a couple of older wires on one regular so maybe it was set up as a partial trickle charger while running? OR - is it the common ground. If you know exactly how the 12V battery is wired to everything, it will make troubleshooting very quick. If I was forced to use a 12V battery to start my car, I would use a double pole contactor to prevent 12V from touching the 6V system while starting instead of paralleling both 6 & 12 volt systems. It is like having your current wife and a much younger, hot woman in the same bedroom briefly....you never know what will happen.....
~Jim
'38 Master Deluxe 2-Dr
*Disclaimer*...All technical advice given is for entertainment value only, and is not to be taken seriously...
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Joined: Feb 2008
Posts: 3,801 Likes: 1
ChatMaster - 3,000
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ChatMaster - 3,000
Joined: Feb 2008
Posts: 3,801 Likes: 1 |
..... Relay connected so that an isolated momentary switch to a relay connects positive to top of starter motor = 12 v Grounded to frame. Can you elaborate a little more on this? I would surmise that your momentary switch connects the 12V terminal to the starter ONLY when you try to start the car, correct? Is anything else connected to the 12V battery's positive terminal at all times? HOW does the voltage regulator and generator draw power from the 12 volt? there are a couple of older wires on one regular so maybe it was set up as a partial trickle charger while running? OR - is it the common ground. If you know exactly how the 12V battery is wired to everything, it will make troubleshooting very quick. If I was forced to use a 12V battery to start my car, I would use a double pole contactor to prevent 12V from touching the 6V system while starting instead of paralleling both 6 & 12 volt systems. It is like having your current wife and a much younger, hot woman in the same bedroom briefly....you never know what will happen..... A great analogy, regarding the ladies. 
1951 Chevy Styleline Deluxe 2 door sedan / purchased from second owner 6-19-2000.
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Joined: Nov 2014
Posts: 194
Shade Tree Mechanic
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Shade Tree Mechanic
Joined: Nov 2014
Posts: 194 |
Jim " It is like having your current wife and a much younger, hot woman in the same bedroom briefly....you never know what will happen....." I think that would be called a dream 
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Joined: Nov 2002
Posts: 7,472 Likes: 26
ChatMaster - 7,000
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ChatMaster - 7,000
Joined: Nov 2002
Posts: 7,472 Likes: 26 |
For sure sparks would fly and I don't think there would be a pleasant ending!
Steve D
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