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
If you turn on the key and you do not hear the pump in the tank running for two secounds ( the same time your warning lights on your dash light up and goes off) then 1 you need to replace the pump or 2 it has low voltage to the pump or 3 both. I just repaired a 1987 pioneer what you need to know is the pump requires 12v at the pump, however OEM has placed an inline ballast resistor located on the driver side front engine compartment near the hood latch that is made of white ceramic with two connection both wires are orange with a black stripe. A. Check the voltage on both sides of the resistor 12v in 12v out use a volt meater - to battery + to resister if no voltes check the relay the passenger side of the engine compartment ( there is 4 relays from front to back it is no. 2 from the battery) looks like a small blue box newer relays are black, if they do not click when the key is on then your CPU may be bad or fusible link is bad If you have voltage to the resister and you have 12v in and less than 12v out your next test will be at the rear connector to the pump, three wires close to the fuel filter using a volt meater check the black wire with the orange / black stripe if voltage is less than the voltage out of your resistor then there is a bad wire in the system and a new wire is required. confirm this by jumping the battery to the pump wire black to- and orange to + the pump should run. Note. running the pump with lower than 12v will damage the pump and cause it to fail! If the pump works you can check the fuel pressure on the fuel rail, remove the cap to epose the shearder valve (looks like the valve on your tires) depress the valve stem and fuel should come out, caution fuel is under pressure have a rag under the valve to catch the fuel, if low pressure the pump is bad and/or filter is plugged Replace filter first recheck this test then replace pump and recheck. Note!!! when the pump is out of the tank recheck the voltage at the pump this will show true voltage at the last connector it needs to be 12 volts! Reconnect the pump wire the stock wire and check, on the pioneer I worked on was 4 volts so I rewired it to a new battery source using the orange /black strip wire that had 12v in to resistor as a trip wire for a 65 amp power relay. The owner noted an increase in overal performance " it now has more power now" hope this helps
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.
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.
There are two fuses for the fan. One is probably a 20 Amp in the fuse panel in the cab and marked "Heater". or "Heater/AC" The second is under the hood may be marked Heater, Blower, or Fan and should be 30 Amp. The one in the cab supplies switched 12 volts to the fan speed switch. The one under the hood supplies the 12 volts to the relay. The relay is normally energized by the 12 volts through the 20 Amp fuse in the cab and through the switch. I think you find that the fan has the normal speeds except for missing HI with the underhood fuse removed, and will turn off with the ignition that way. There is no hazard in operating it that way but you may want to replace the resistor/relay assembly before it gets too cold. The relay is a pretty trouble free device in most cases, maybe you can find a deal on a good one at a junkyard.
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!