Charging System Question

[240ClassicMH]

After reading other posts I've had the multi meter out and am still unsure if I need a new starting battery or alternator.

After jumpstarting the moho, disconnecting cables and left running, no load from dash;

Isolator: 11.1
Starting Batt: 11.0
House A&B: 10.7

Running Heater Fan

Starting Batt: 8.3

Fan and Headlamps: 4.6 (dash voltage guage drops to zero)

Turn off Fan and Headlamps, engine still running

Starting Batt: 6.5

Cut Engine

Starting Batt: 10.3 ... but won't start - dash gauge doesn't register


Any advice, tips and or tricks much appreciated. I'm low on electrical knowledge.

[TG Twinkie]

You are not charging the batteries. The output voltage from the alternator should be around 14.5 volts. Even if the battery is dead.

[arcamedies]

How old is the starting battery (plus 3 years) ditch it and get a new one. Battery should be at least 12+ volts to start an engine. If you fully charge the battery it should hold charge for sometime even if the alternator isn't working properly. The alternator needs voltage from the battery to operate as well.

[240ClassicMH]

Thanks for confirming.

Will get out the tool box and start cranking.

Is this a 2 beer job or is that wishful thinking?

[240ClassicMH]

Originally Posted by arcamedies

How old is the starting battery (plus 3 years) ditch it and get a new one. Battery should be at least 12+ volts to start an engine. If you fully charge the battery it should hold charge for sometime even if the alternator isn't working properly. The alternator needs voltage from the battery to operate as well.

I will be replacing it as I'm not sure of its age - the house batteries are new. I figured its not the culprit though if a 30 second jump start gets it to 11.1 and it holds until I run lights and heaters?

[bkahler]

Originally Posted by 240ClassicMH

I will be replacing it as I'm not sure of its age - the house batteries are new. I figured its not the culprit though if a 30 second jump start gets it to 11.1 and it holds until I run lights and heaters?

Odds are your alternator is bad. Let things sit over night and then take a reading on your starting battery. If it's good it should recover some. If you charge the battery over night with a trickle charger it should be good enough to start the engine and if it doesn't then it is likely bad. If it does start the engine then as mentioned previously by Twinkie you should have 14+ volts (absolute minimum would be 13.5) at the alternator output connection when the engine is running.

You can get your battery load tested at just about any Automotive parts store.

Good luck!

Brad

[240ClassicMH]

Thanks for all the speedy input - when I drove the truck around back expecting I would be pulling the alternator I found a shredded belt on the ground and sure enough no belt on the moho.

Had a new spare onboard so we're back up and charging as per normal.

Went for a trip to the gas station to fill up and fires up no problem. Will replenish the spare belt supply tomorrow - this one was 6 mos old with about 1500kms on it so will check the pully aliignment before any longer trips.

Thanks again to all. Happy motoring.

[bkahler]

You got lucky. Last time I lost a belt, when it broke it took out the other two and at the time I was doing 65 mph in the middle lane passing a semi. All of a sudden no power steering, no power brakes and no water pump. Not fun

Glad to hear it wasn't your alternator or the battery.

Brad

[arcamedies]

Originally Posted by 240ClassicMH

Thanks for confirming.

Will get out the tool box and start cranking.

Is this a 2 beer job or is that wishful thinking?

Step 1. cool beer in ice at least a six pack
Step 2. invite a friend who is mechanical over
Step3. charge at least one battery seperate from the others and use as starting battery, even if you have to pull it out of your car.
Step 4. start coach and see if battery remains above 12 volts, if not alternator not putting out. Go get a rebuilt one from any auto store.

Generators spinning produce voltage above 1000 rpm, alternators without 12 volts hooked up will do nothing without input from voltage source. A battery at 11 volts is not a good source.

[arcamedies]

oops missed step 5 after just reading last nights post I missed, my bad.

Step 5. CHECK TO SEE IF BELT ON ALTERNATOR. LOL now drink all of beer.

[240ClassicMH]

Step 5 under way. Sitting at Porteau Cove about an hour south of Whistler in a beautiful spot on the water and hooked up to keep the bevies cold. Even the net connection is excellent. Awaiting a Pacific storm front to roll in with 90km hour winds and 100mm rain.

No such thing as a bad day in an Airstream.