Over charging 24V batterys

Jtomcollins5 · May 19, 2019, 07:46:20 PM

Made a test run in my 1974 MCI 8, 8V71 Custom Coach Conversion. The batteries got so hot that it blew some of the fill caps off. I think the generator is overcharging is there some kind of regulator to control that. Are the batteries junk now.

thomasinnv · May 19, 2019, 11:01:11 PM

In the rear baggage compartment is located the voltage regulator. Put a volt meter on the batteries with it running and see what you've got.

richard5933 · May 20, 2019, 03:10:00 AM

If it's a Custom Coach odds are that you have a voltage gauge in the cluster over the driver. It may or may not still work. Mine does - more accurate than the dash gauge so I watch it instead.

Your voltage regulator should be adjustable. Batteries may be good, but I'd be very suspicious.

neoneddy · May 20, 2019, 03:35:06 AM

Fill the cells with distilled water. Measure the voltage while charging. Anything over 29 and you will have issues.

DoubleEagle · May 20, 2019, 05:32:33 AM

If the batteries are being overcharged it is either a voltage regulator problem, or the generator was wired incorrectly and it is putting out constant maximum current.

buswarrior · May 20, 2019, 05:36:44 AM

how much liquid was in the batteries before this started, and/or now?

You need a good multi-meter, go get one and learn how to use it so you do not burn it out.

You can't choose a cause until all the symptoms have been identified.

Don't start screwing around until you've got the diagnostics asked for, or you'll just make things worse.

happy coaching!
buswarrior

Jtomcollins5 · May 20, 2019, 08:23:01 AM

The the batteries were new and full of water, there is a voltage gage in the council above the driver I do think it was showing over voltage but I didn't realize it was that high. Going to pull batteries out clean up and fill with distilled water. I can check voltage 29 or under with multimeter. Is the voltage regulator adjustable and is it located in the engine compartment? The next bay forward is where my generator would it be in there? It was late last night 10:30 when this happened. Thanks for the replies and help.
Where do I check power steering fluid did not see a reservoir in the front compartment under the driver seat.

neoneddy · May 20, 2019, 08:35:08 AM

Voltage regulator on an MCI and some GMs looks like this http://www.mcicoach.com/parts/coachGuard/voltageRegulatorBoards.htm

On an MC( it's on the passenger side, back of the last bay. Might need to remove a few bolts to remove the protective cover. There is a nut protecting the middle of it, that is the where the adjustable potentiometer is. Use a small flat head screw driver to twist it, if I recall it's clockwise for my power, counter clockwise for less. On my bus I could hear the engine unload when I turned it down too far and then hear it load up again when I gave it load. There are 3 wires on it, ground, positive, and field, it's the field voltage that it is adjusting. Take your measurements on the positive terminal. Watch that that field is not connected to the positive, that would be full field and it would be running unregulated and cooking your batteries. I did this to test mine when it was failing, in a pinch you can do it, but it's not a way to live. Lastly you can measure the voltage from the field terminal, that can give you a sense of the health of your alternator I think. When mine was barely putting out 20 amps or so I was giving it a full 26 volts or so to the field, now with my new alternator I'm feeding t 4-6 volts to get 27-28 volts output.

Power steering reservoir should be on passenger side of the engine, might look like a coffee can sized container with a sight class on it.

Jtomcollins5 · May 20, 2019, 09:34:00 AM

Thank you for that information. The picture will help me to find it.
I just inherited from my father, been setting for about five years. I pretty much got it ready to go. He had it about twenty five years.

Jtomcollins5 · May 20, 2019, 04:43:43 PM

Got home and did my testing found voltage regulator turned it all the way down as low as it go. Put multimeter a voltage regulator still real high.I switch the field and power wires around and I'm at 28.5 at the voltage regulator and 30.06 at the batteries off fast idle.

neoneddy · May 21, 2019, 08:56:56 AM

Sounds like the regulator crapped out. The manual shows ways to test it and repair it. It might be worth taking it apart and inspecting the board (it's 8th grade basic electricity complexity). Look for anything obviously burned or shorted.

Another route to go might be replacing it with a newer digital version like https://www.ebay.com/i/292868582384?chn=ps . I'm not familiar with these in practice, but I looked at it when I was having my issues.

Jtomcollins5 · May 21, 2019, 03:11:14 PM

I looked up a test in the MCI manual it said to start engine, 110 PSI put on fast idle and check the field terminal tested ( 58.5 )on positive terminal tested ( 59.1 ) .Would alternator burnout the voltage regulator and do I need to get the alternator bench checked also. The voltage regulator that you posted look great going to order it up. Thanks again for all your help.