picked up a 55 merc a few months ago and drove it home. next day it wouldn't start. replaced the battery. had an 8v in it. rebuilt the starter, changed the solenoid. replaced the 4g battery cables with 2/0, rebuilt the generator. my question is what is an acceptable charge voltage in it. with the regulator that was in it i get 7.08 at the terminals max. with the new regulator it reads anywhere from just under 7 at idle up to 8.8. sometimes it reads 8.8 at idle sometimes only above 1200rpms. if its reading 8.8 at idle i can shut it off and restart it and sometimes that will bring it down below 7. im new to 6 volt systems and need some help. telling me to go to 12v is not help. i know its more reliable but the car only has 34,000 miles on it and i'm trying to keep it period correct
You can run on 12v and still look "period correct". They make 12v generators. I chased gremlins on my 6v system for the first 3 months I had my 49, before I finally threw in the towel. I'm probably wrong, but I don't think you're supposed to have that much voltage at idle. Sounds like you've got a draw/short somewhere.
A 12V system charges 13-14 volts so I'm thinking that you are not getting too much charge. Your car is using part of the voltage and the battery works as a buffer.
It sounds to me like the previous owner put in an 8 volt battery and then messed with the regulator adjustments to get it to charge 8 volts. Personally, I'd go back down to a 6 volt battery and readjust or replace the regulator. Some guys will advise you to step up to 12 volts.
You have a 8 volt battery correct ? You need to have the voltage regulator adjusted to give about 8.8 volts at 1500 RPM with a FULLY charged battery. A new 6V regulator out of the box will not be corectly set. With all you have repaired/replaced put a GOOD heavy 6V battery back in the car and see how it does. 8V batteries are a pain as the needed voltage to keep them happy plays hell with the rest of the system. BTDT !!
i drove my 49 merc for two years until changing over to 12 volt with no problems.turn on the accessories that you will be using when driving,lights,radio,etc. then check the reading with a multimeter not the gauge.8.5 volts while driving and 6.5 to 7 at idle is fine.at idle with lights on should pull it down to battery voltage then charge when raising rpms.i just changed to 12 volt to get a stereo and ease of finding bulbs and jump starting.another trick i learned is to glue a penny on the top of the battery with silicone and the corrosion that usually gets on your cable ends goes to the penny and when it is all gunked up just scrape off the old one and glue on a new one.the hydrogen gas that carries sulphuric acid will corrode copper first over the lead cable ends.
hellbillyhotrodder......DID you put a 6v or 8v battery in the car??????????? If you put a 6v in then you are good to go..... 7 to 8.8 volts is good. IF you put the 8v battery in you will have to adjust the voltage up to near 10 volts to run accessories and to charge the battery.
i put a 6v battery back in it. after reading posts for the past couple of months trying to troubleshoot all the bugs that i have worked out everybody said an 8v was a crutch. i'm getting 8.8 with the new regulator 7 with the one that was on the car. the problem is that it will be getting 8.8v at idle sometimes. if shut it off and restart it sometimes it will kick down to just below 7v at idle. all reading were with a multimeter at the battery posts
If your idle is below 750-800 RPM your generator is not charging . Battery voltage at that point should be about 6.2 or a bit higher with no load. Max charging voltage with a fully charged 6V battery should not be over 7.6 or you will be boiling the water out of your battery. I think your volt meter is not reading correctly. Get a "Motor's " or Chilton manual that covers the year of your car and read up on the correct way to trouble shoot and adjust the regulator. If you are using a Optima type battery those usually need the regulator set up a bit higher to fully charge like 7.8 max.
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