Tip & How-To about 1996 GMC Yukon

Voltage draw down found!
1) repaced bad battery
2) rechecked voltage draw still showing 12 volt drain with all under hood fuses, relays, and interior fuses and relays pulled.
3) Computer was the 12 Volt drain, & had to reprogram itself.
4) gave the new battery a good long charge, reinstalled the battery into the vehicle.
5) Hooked the battery up, pulled the keys out of the ignition, close and lock all doors with auto door lock. Waited minimum of 20 min so the computer would go back into the sleep mode.
6) after 20 minute wait, rechecked the voltage draw by removing the neg battery cable from the battery, hooking volt meter + lead to battery cable end, and neg lead to battery neg post, nothing showing or zero reading.
7) Hooked the neg cable up to battery, started the truck and let the engine idle to normal run temp, then fast idled 1200-1300 rpms for 2 minutes, then drove the vehicle for 5+ miles and alternating speeds. All appears back to normal now. Alt showing 14.2 to 14.4 volts, and no other problems.
After all of the afore mentioned, my problems began with a bad battery cell, thus caused my computer to have the memory reset.Until the computer was reset, I had a 12v continious draw down! I got this info from a repair manual, that I purchase sometime ago. Thanks for your alls help........EJB

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Battery running down.


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The battery keeps going dead in my 03 z71, only thing out of place is i cannot shut off the headlights manually anymore,it's stuck in auto. Alternato is fine and so is the battery, drains iin about 7 hours.


Well if lights are not staying on then you have a draw of power somewhere. Easy way to find out is volt meter. You take off negative cable and put one end of meter to battery post and other to wire dont let the wire touch post or anyother metal of vehicle. Then go through your fuse box and pull fuse's one at a time until you see voltage on meter drop. Meter should should a (-)negative voltage at start and get smaller when right fuse is pulled take notes and pull all one at a time and replace back in orginal spot. If you find one that really lowers the negative voltage draw on meter good chance you found where problem is. Id start by checking all interior lights first, including glovebox.

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Something is draining the battery


You have a draw and a draw pulling more than a couple hundred milliamps.This will drain the battery in an objectionably short amount of time.. All the things you mentioned and more can cause this draw. The best diagnostic step towards isolating your draw is with meter that reads Volts DC or better yet a test light.(I think) ..disconnect B+ positive battery cable. Install meter or lamp in series with disconnected cable and battery post. You do have some smal draws like computer memories,clocks etc which will show a low amount of voltage hence a very dim test light. If you are drawing heavy ,obviously the meter will show a full blown 12 volts and the lamp bulb will be very bright. Remove fuses,unplug relays,dis-connect devices while watching the voltage or lamp.You should begin to isolate offending item once the circuit has been detected, Generally pulling all fuses individually will tell you at least which circuit is pulling the amps.

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The whole idea with the relay under the hood started back in the Sixties believe it or not. There is considerable voltage drop in the wiring between the fan switch and the blower fan motor. By adding the relay under the hood right next to the motor, the voltage drop was reduced, both by the shorter wire, and by using heavier wire to boot. The motor gets really close to the full system voltage when the relay is closed. In your case where the relay keeps the fan running, it can drain a battery rather quickly too!

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