I have a constant draw when fj is running. Stronger draw when using anything electrical, headlights, directionals, break lights etc... alternator was tested good and battery was replaced. I cleaned all major ground connections I could find. Ideas? Thanks. Jeremy
77 fj40 electrical problem (1 Viewer)
- Thread starter Jsmith43
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1911
chupacabra
that sounds normal; what exactly is the problem?
- Thread starter
- #3
I believe the draw if more than normal. The truck only can go a few days without having to charge the battery manually. If I run it at night and use the headlights it’s less than that. Headlights or dim while using. The needle Volt meter on the dash moves into the negative end substantially with the more electrical things you use.
GA Architect
SILVER Star
Are you sure your alternator is getting power back to the battery?
1911
chupacabra
Are you running the stock alternator?
It could be one of several things; could simply be a bad (old) battery, sulfated up and won't hold a charge any more. Could be your ground cables are old and weak. Could be the battery positive cable is corroded with copper sulfate. Could be your voltage regulator is faulty, could be your alternator is faulty. Could be you have a parasitic drain somewhere even when the truck is turned off (especially if you have any non-stock accessories wired in).
If you have a basic multimeter, there are a number of voltage tests you can do to ascertain the basic health of your battery and alternator; I would start there. You can find how to do these pretty easily on youtube (easier than I can write them out for you here).
Do some easy things first.
Make sure all connections at battery are clean and solid. Ground connection to chassis/engine is good. Connection at alternator is solid.
Parasitic draw is easy to test for. Disconnect ground battery terminal put a test light between terminal and cable see if it lights. If you don’t have a modern radio or fuel injection you shouldn’t have any light.
When the alternator was tested were the diodes tested (regulator)? If You have a bad diode you will see a draw on the test light.
Could be as simple as a slipping alternator belt
Make sure all connections at battery are clean and solid. Ground connection to chassis/engine is good. Connection at alternator is solid.
Parasitic draw is easy to test for. Disconnect ground battery terminal put a test light between terminal and cable see if it lights. If you don’t have a modern radio or fuel injection you shouldn’t have any light.
When the alternator was tested were the diodes tested (regulator)? If You have a bad diode you will see a draw on the test light.
Could be as simple as a slipping alternator belt
- Thread starter
- #7
I thank you for all the info. The alternator is a aftermarket Bosch. I think that the FJ was worked on before I owned it. It has had the problem since day one. Replaced the bat and checked the alternator. Bat reads 12.6 when truck is off. 12.2 when it’s running with nothing electrical on. A small increase if I accelerate the truck but not anywhere close to 13 or 14 volts like I believe it should. I’ve cleaned and replaced all ground and positive cables and ground straps. Possibly the regulator? Regulator does not look original with what I find online. Also could the alternator not be grounded properly? Happy to send pictures if you think this would help.
Any update on this? I’m having the same problem with my 77 cruiser. New battery, new battery cables, and I’ve checked that the alternator works properly. I think there’s a parasitic draw. I haven’t changed the voltage regulator, but could that kill the battery when the cruiser is off?
You say that you've checked that the alternator works correctly.. you mean you've tested the battery voltage to be around 14V when running?
There are only a few hot circuits when the igniting switch is off - try pulling those fuses (stop, turn, engine).
If your battery is dying overnight then that's at least a couple of Amps - when you remove/replace the fuse then you'd expect to see a spark. If everything is isolated then you won't see a spark.
Let's see photos of your alternator, regulator, and battery setup
I believe it’s all stock. I did have to rebuild the alternator wires to the voltage regulator. The Po must have melted them. Hence the new wires. I worked with coolerman to make sure my wires were correct. But the problem persists. It’s currently on a trickle charger.
So do you get 14 volts when running ?
corcel
SILVER Star
This may be a silly thing, and I'm not experienced enough to know why it happens or if it could help -- but on my 77 I have to jump the RPM's fairly high at the start before the indicator jumps to charging. If I don't do that, it runs on a constant draw.
fjwagon
SILVER Star
I agree, if the battery drawing current (load) when the ignition is in the off position, you may have a stuck relay or shorted component, see post #6, remove the negative battery terminal and complete the circuit with a lamp. If the lamp is comes on, you have a circuit that is drawing a load. Start disconnecting connectors or fuses until the lamp turns off.
I would Use same the logic if you have 12v when off and 12.2 when it's running. The first thing I would check is make sure voltage regulator is working. Also make sure you have good connections at the circuit for the alternator to battery and ignition. If there was a short at some point I would not rule out a cold solder joint or a bad connection in the harness. Or maybe too many broken strands on a wire but enough strands that a continuity test will pass but not enough strands to handle the load. It will almost act like a resistor hence the voltage drop in the harness. May be able to check it by ohming out instead. Sometimes jumpering from to point to point in the circuit and hope to find it that way.
I would Use same the logic if you have 12v when off and 12.2 when it's running. The first thing I would check is make sure voltage regulator is working. Also make sure you have good connections at the circuit for the alternator to battery and ignition. If there was a short at some point I would not rule out a cold solder joint or a bad connection in the harness. Or maybe too many broken strands on a wire but enough strands that a continuity test will pass but not enough strands to handle the load. It will almost act like a resistor hence the voltage drop in the harness. May be able to check it by ohming out instead. Sometimes jumpering from to point to point in the circuit and hope to find it that way.
South Texas 97
GOLD Star
I believe the FSM has some diagnostics on the Voltage regulator - given that you have replaced the wiring from the alternator to the regulator, it might make sense to take a look at the regulator next.
