Batteries won't stay charged

[beniam]

Have 1980 Kings Hiway 34ft class A with a 440 engine.I have replaced all batteries one in the engine compartment,and 2 new coach batteries.The problem the motorhome starts and drives, but when I turn the ignition off the motorhome will not restart. All the batteries are discharged. I have removed the alternator,and have had it checked,and it is ok. Replaced a fuse in the converter.. Have changed battery cables. Any help to determine the cause of the battery drain would be appreciated..

[joeprinter]

beniam wrote:
In answer the the last posters' question, I recharge the batteries, the MH starts,and I drive it a few miles , and if the motorhome dies it won't restart.This is especially cumbersome in traffic.. when I return home and and shut it off, it won't restart..The battery is down.Thank you..

I suspect the alternator is not charging or else the battery isolater is not functioning.

[beniam]

In answer the the last posters' question, I recharge the batteries, the MH starts,and I drive it a few miles , and if the motorhome dies it won't restart.This is especially cumbersome in traffic.. when I return home and and shut it off, it won't restart..The battery is down.Thank you..

[dad4papa2]

A little more info please. Are you saying you can start the engine then drive a few miles shut it off and then it won't restart or does it start and you drive it a ways and shut it off and it won't restart a week later. This could indicate many different causes depending on your answer.

Dad

[beniam]

I appreciate all the responses to the problem listed. I will check the areas suggested this weekend.The batteries are being charged now. Also my voltmeter needs replacement, my old sears isn't working..I will keep you posted on the results. Thanks again for your help.

[JimM68]

do you own a voltmeter?

you's going to need one for this. You can buy a cheap digital DVM at any home center or hardware store for less than $50.

You want to check and monitor voltage at:
(neg meter wire to a good ground.)
Battery.
Alternator.

you should have more than 14v at each.

I agree with the posters above that your diode type isolator is probably bad. A few simple tests will nail it down.

[MrWizard]

are the batteries going dead while sitting
or do you mean , they go dead while you are driving, and the only thing keeping the engine running is the alternator, and there is no battery power for restart
they should not die that fast unless there is a short circuit someplace

1980 has a electronic voltage regulator near the fire wall or mounted on a stanchion at the back of the engine under the dog house

measure the voltage at the batteries with the engine running, then at the alternator

i suspect the 'diode based' battery isolator is the culprit and has burned out
you can get a new one at pep boys, or camping world

the isolater will be mounted up front under the hatch
or
near the engine battery if its some place like under the steps

one other thought
does your kings highway have a large knob/switch near the floor of the drivers seat, labled main aux both off
be sure to place on both when starting and driving
that is a 'marine' battery selector switch

[Jim]

What does the black box control, PuterPuppy?

[PUTERPUPPY]

Older Dodge chassis have a small black box on the firewall, much like the old regulators with 2 wires. Try to cross over this box. I always carried a straighten paperclip for just such a problem. If it starts up you know what to change.

[crasster]

Does it have a battery isolator?

Check that first.

[Jim]

In older RVs there is a diode that goes from the fuse block to the alternator, usually it's spliced in the wire just before the alternator. That FIELD voltage is what tells the alternator how much voltage to output to charge the batteries. The voltage source to that device is from the batteries. If it is open circuited (diode bad), or if a connector is bad, or the wire broken, or even a dirty connector at the fuse, that will cause your symptoms.

Test is to put a meter on the starting battery a few minutes after you start the engine. You should be reading 14V or so. Nothing less then 13.2V though.