battery issues wont start

[Huckleberry]

Need Help- 1978 GMC K15 350ci engine. Truck has 2 batteries. Batteries have run dead over night, 10 volts on the meter. I can jump start the truck and the batteries will carry 11.3 volts, then you can here a very noticeable click ( like a metal ping). The volt meter will jump to 13 or 14 or higher volts, the motor changes a small rpm amount. Then after a few seconds, another click and the volts drop to 11.3 or 11.5. The "click" sounds like it is coming from the drivers side firewall???? Keeps repeating this. You can also here the clicking noise inside the cab under the dash. Also, when you turn off the truck on the low voltage " click" the entire truck is dead with the key turned on ....... After you here the "click" again, the truck will start.......then start to repeat the whole low voltage /high voltage clicking deal . Please help. My wife bought this truck for me 4 months ago( My dad had one) and has run great.

 

[Snoots]

Sounds like the battery (not starter) solenoid is dying.
Disconnect the drivers side battery and give both a good charge.
Run it with the single battery.
Keep us posted.

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[SquareRoot]

Why does it have 2 batteries?

 

[Huckleberry]

Thanks Snoots. I'm not sure why the 2 batteries SquareRoot???? I'm gona guess maybe the previous owner had a snowplow on it.? Update, I removed the extra battery. I have a trickle charger on the remaining battery. charger is reading 13.1 volts. Gona be a cold night here....... keep ya'll posted. Appreciate ya'll

 

[Snoots]

Why does it have 2 batteries?

Usually (I believe) diesels had 2 batteries.
Mine has 2 but is not a diesel. Probably added by previous owner. He was stationed in Alaska for a time.

 

[Ricko1966]

The click followed buy a voltage change,I'd be looking for a relay,probably a battery isolated making the click. It probably gets signal from an oil pressure switch or the alternator.You turn the motor enough, the relay closes thinking the engines running,both batteries are now providing voltage,the relay figures out the engines not running and the relay opens now your back on one battery. Test both batteries and check for a voltage draw. I bet you find a voltage draw.

 

[Huckleberry]

Thanks, I'll check that asap. Appreciate you