1984 Tercel SR5 Battery Drain

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My tercel:: 1985 Tercel 4WD

1984 Tercel SR5 Battery Drain

Post by Tman312 » Sat Nov 03, 2018 7:16 pm

Has anyone experienced a parasitic battery drain with their Tercels?

Looking into my mom's tercel, it will drain the battery in about 8 to 9 hours. Confirmed it draws when key is off.

When running, I get 14v at the alternator but only 13.5ish at the battery terminal.

Just looking for areas to start looking if there is a common issue.


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My tercel:: '84 Tercel4wd w/extensive mods
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Re: 1984 Tercel SR5 Battery Drain

Post by Petros » Mon Nov 05, 2018 3:37 pm

sounds like the alternator is operating normally. this is not common on a Tercel, there should be no draw when it is off (not like modern cars that have all kinds of equipment that needs power to maintain memory and function even when it is off). check that all of the lights and switches are off, check for corrosion at both ends of the battery terminals.

it is a fairly straight forward process to isolate a voltage draw. use an amp meter, or even a light bulb with two wires, see the FSM. you work backward from the battery terminals. often, when there is on obvious cause like corroded battery terminals for faulty switch, the cause is grim and corrosion built up on the fuse and relay blocks both under the hood and under the dash. Much of the under-hood grease and grime build-up has metal partials that can short out at the contacts in the system.

Once you know there is a draw when the ignition is off, you can try a quick cleaning of the terminal blocks with tuner clear, or carb cleaner, followed by blasts of compressed air (if you have a compressor handy), and than spray all surfaces, terminals, fuse boxes with LPS, or similar di-electric corrosion inhibiting compound. These kinds of sprays actually improve contact without causing a short, and prevents corrosion at the contact.

As a car ages, particularly in damp climates (like where I live in the PNW), all terminals are subject eventually corroding, so I consider applying corrosion inhibiting compound a necessary maintenance item. I regularly apply it the battery terminals, and spark plug wires and contacts, which seems especially prone to getting corrosion build up. if you find any terminals with excessive corrosion, it should be separated and cleaned of course.

if a quick cleaning of the terminals and obvious contacts does not help, than you have to track it down systematically using the wiring diagram found in the FSM. often times components like switches, relays, etc can get internal corrosion and cause a voltage leak. check the obvious items first, and work down the wire bundle from their. It actually does not take that long to do, but it is important to do it systematically, without rushing the process, until you have isolated the source of the voltage draw. once you find the source of the draw, almost always fixing it is simple. Many of the switches and terminal blocks can be disassembled and than you clean the contact surfaces with a fine abrasive like scotch-brite pad or fine steel wool (make use you clean out the dust and particles when done). if the internal contacts are corroded away you will have to replace the component.

Good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Re: 1984 Tercel SR5 Battery Drain

Post by xirdneh » Mon Nov 05, 2018 7:05 pm

i remove a battery cable , then barely touch the terminal to the battery, if there is a small spark something is turned on
then the search is on to figure out what it is
most of the time its one of the dome lights
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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Re: 1984 Tercel SR5 Battery Drain

Post by splatterdog » Wed Nov 07, 2018 6:04 pm

The method Petros described is best done with an ammeter put inline with a battery terminal and then pulling fuses one at a time. The spark when attaching a battery cable is not a good indicator, unless she pops good. A T4 should have no more than 10-20 milliamps at rest, maybe less. Modern cars loaded with computers can be as much as 35-50. At least it's a T4 with a microscopic electrical system. Most of my parasitic draw battles now are on circuits with 10-20 different loads. Last one had 17 branches off the one fuse that was drawing. Took half a day to disconnect them one by one, and of course it was almost the last one that was it.

I had a draw on one of my 70's Ford trucks once. Turned out the field in the alternator was kept hot due to a couple contacts in the ignition switch had worn enough copper off to bridge them together.

A thermal imager can help too. Car must be completely cool for the hot component to stand out.

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