unable to use headlights without draining battery

NYET )

Voltmeter. At the isolator (the type with fins and three studs)

Start engine BE CAREFUL. Select VOLTS

Touch Positive test lead to CENTER stud on isolator

Touch NEGATIVE test lead to EACH outer studs. Scrape through corrosion

Do you read voltage higher than 1.1 volts on ANY of the two studs check?

If YES the isolator is BAD. Scrap it.

If you can't use headlights without killing battery one of two conditions exists.

1: On older cars with "V" type fan belts the blets do stretch as they age and need to be re-tightened. (1:B on one car I had they put on the wrong belt).

2: If you have a serpentine belt, and it has not broken (They do break on occasion) then the alternator has failed and needs either rebuilding or replacement.

I have one of these to let me know what is going on with my electric. You will be able to know what is happening at all times. I had my alternator fail going from Reno to Klamath falls. I found a Napa and put in a new alternator in the parking lot. My rig waas a 86 Chevy class C.

With a voltage monitor you will be able to see what happens when you turn on different accessories.

I agree with other posters that 63 amps is not enough. Mine I beleive was 90 amps. You can easily go above 120 amps as well. High amp alternators do not perform as well at idle as lower amp units and that is the caution for a higher amp unit.

When I had my class C I was checking amp usage of different accessories with my clamp meter and the headlights use up a lot with all the clearence lights ETC. I think it was pushing 40 with the headlights on.

I made it to Klamath falls, after the alternator failed, by running the gen and letting the converter assist the alternator to keep my volts up.

Paul

I would also recommend a minimum 90amp alternator. Your factory rated 63amp alternator only puts out that much power at max rpm when cold. When it warms up the efficiency goes down to about 50a.p at max rpm. Driving around output probably about 40amp.

The following are round numbers:

Engine 20amp
Heater 20amp
Headlights 20amp
Radio 2amp

Unknown power for recharging two separate batteries.

Most alternators are cold rated. The special ones are hot rated. Meaning it's tested after its warmed up. I have a 160amp hot rated welding alternator in my jeep.

Alternator should keep the battery charged in all conditions. I am thinking the alternator is weak or shot.

dgcarousel wrote:
We are getting 12.2 to the starting battery when the engine is off and 12.4 when it is running. The alternator to the house battery is just over 13 volts. Sounds like I need to have to get the battery and alternator replaced. This something I can do with a little muscle help.

DG,

You have something wrong in the charging circuit. Without being there to run the checks I normally would for a client, I cannot tell you where. Your current alternator should be adequate to the load you have.

The readings you post tell me that something is wrong at or about the isolator. When the main engine is above idle, the voltage measured at the two outer posts of the isolator should be very close and the center that is connected directly to the alternator should be about 0.6V higher.

A resting fully charged 12V battery should be 12.6V.
A battery needs to get to a terminal of 13.6~14.2 to charge very much at all.

Good Luck Guy

Matt

Most auto parts house and tire outlets will test your batteries (both coach and chassis) for free - that would be my first stop. Also have the alternator tested as it sounds like it needs replacing or wiring is amiss.

We are getting 12.2 to the starting battery when the engine is off and 12.4 when it is running. The alternator to the house battery is just over 13 volts. Sounds like I need to have to get the battery and alternator replaced. This something I can do with a little muscle help.

Do a couple of easy checks before you start throwing money at it. Measure your battery voltage at the starting battery with everything turned off. Hopefully it is at least 12.4 volts (should be 12.6 or greater). Then start the engine and remeasure volts at the battery. Should be well above 13.6 and likely 14.5 or so. If this measurement works then turn on everything you can think of. Remeaasure voltage both starting and house battery. The alternator should keep voltage roughly the same as the original running voltage. If the alternator doesn't put out close to 14 volts with minimal load and maintain that voltage with everything on then your alternator is not working correctly or not large enough. 63 amp seems low so if you do replace I would get at least a 90 amp if not larger, and no there is no such thing as too large within reason.