Joined: Aug 20, 2010 Posts: 122 Location: Illinois
Posted: Mon Mar 11, 2019 4:08 pm Post subject: Low voltage at battery.
The battery’s are around eight years old but look in great shape as in no corrosion or anything. Went to fire the beast up today and it didn’t turn over like it did just a couple of weeks ago. Checked the voltage on both batteries and they were a little under thirteen volts each. Checked from the the starter to ground and got twenty six or so. I really really hate electrical issues so what manual should I be looking at or any suggestions first. I will be reading and using the download —testing the 24 volt system 1956 — later tonight. Thanks John Jr.
1952 M38 _________________ 52 m38
I recall I left it on the battery the first time a good 72-96 hours to get it back to life. Now I give it a 24-hour maintenance treatment at least once a quarter whether I use the battery or not. It's still good today. My M38 converted to 12V so I only use one battery.
I'm using their model 1510.
Good luck! _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
1954 M100 Dunbar Kapple M750759 dod 1-54
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
John, This is probably a good time to read up on good old general vehicle electrical system maintenance. The simple things are often overlooked while we overthink our problems.
1 - Use a digital VOM meter for taking voltage readings. The better the tool the better the readings can be relied on.
2 - A fully charged 12 volt battery will usually read 12.8 to 13.2 volts. Don't laugh at those .8's and .2 readings. You'll realize the importance of detailed readings like that as you learn the art of electrical troubleshooting.
3 - Next take a reading of each cell's electrolite level and specific gravity for both batteries. WRITE Them down! I also take individual cell voltage readings and record them.
4 - Google "Battery Testing" and learn how to interpret the specific gravity readings. If voltages and specific gravity readings show no problem then move on to an inspection of all electrical connections for cleanliness (no corrosion) and tightness. Don't overlook grounds. Make sure there's a ground strap between the right front engine mount and the frame and that its connection is corrosion free and tight.
5 - Now google "Voltage Drop Testing". Learn how to do it and then do it. It helps to have an aligator clip at least for the ground probe on your meter. I prefer to disconnect wire # 12 from the coil and while cranking the starter measure voltage at each accessible terminal in the circuit. A noticeable drop at one point will usually indicate that there is a problem at that point.
6 - If all is well at this point you are probably facing a starter issue. Pull all the wires off the starter. Select the Ohms function on your meter. Put one test lead on the terminal post the big battery cable was on. Put the negative test lead on the starter's case (ground). If the meter shows an open circuit that is good. Now close the switch and if the meter shows very light resistance then again all is well. If the test meter shows continuity with the switch open or very high resistance with the switch closed then you will have to open the switch and clean, repair or replace the contacts. If the switch checks out good then the next step is: At this point I usually remove the starter and have it bench checked at an auto-electric shop.
Let us know what you find and even show us the readings you recorded.
One note on good batteries. Any pair of batteries that are operated in series together will normally seek a common level voltage between them when not in use for awhile. A weak battery will pull the voltage reading down on the healthy battery. So my advice is always take individual battery readings after both batteries have set for several hours without being connected in series. You should practice this method during tests 1, 2 & 3. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Aug 20, 2010 Posts: 122 Location: Illinois
Posted: Tue Mar 12, 2019 1:45 pm Post subject: Low voltage battery
Well messed with the jeep some this morning. Cleaned the frame ground real good. Looked at the battery’s and one cell completely dry in each battery and one cell looked like it was full of crud in each battery. Threw some distilled water in them and charged them for about and hour. The cowl battery would only charge to 82 percent according to my battery charger, oh I disconnected both battery’s before charging. Before charging the cowl battery while running was fluctuating between 11.81 volts and 13 something. The front battery was about the same. After charging they ran about 12.33 volts to 13.10 volts. Going to buy a hydrometer tomorrow but the battery’s really look kind of cooked to me. Thanks John jr
Well bought the hydrometer today. I think they need to make the numbers alittle smaller. Lol so there seems to be an adjustment that has to be done according to the temperature in the man cave oranywhere else I guess. The cells varied from 1.17 to 1.25. With the adjustment. Sorry forgot to write them all down. Tomorrow I’m going to take the batterys out and clean the starter connections up and get new batterys. Also think I’m going to invest in the Bosch 3.7 24 volt charger. Thanks again. John Jr. _________________ 52 m38
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