hey guys, very new to this forum. I have a 1991 lj79 prado that i bought from cars and bids. It’s a Venezuelan import with a very bad electrical drain. I have gotten the alternator rebuilt and put it back in myself and the car started just fine for a couple days but now it’s back to like before. After a night of sitting it doesn’t have enough juice to start. Now i know it’s probably a very simple fix but I cannot for the life of me figure out where the drain is pulling from. Ive replaced every fuse in the interior fuse box, but there is no fuse box in the engine bay(it was removed?). Any help on this would be a massively beneficial to me. I like to think i am mechanically inclined but am not good with the finicky wiring.
Lj79 prado electrical drain help
- Thread starter AlmightyAdan
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Do you have a multimeter? The fastest way to find what part of the wiring is drawing power is to use a multimeter and watch the amperage drop to zero when you remove the correct fuse. Then you can check just that section of the wiring harness and find the culprit. It usually comes down to a PO DIY fix or mod (likely stereo related)
Google "finding a parasitic power drain on a vehicle" and that should point you to a good how-to with a multimeter. Best of luck finding this gremlin!
Google "finding a parasitic power drain on a vehicle" and that should point you to a good how-to with a multimeter. Best of luck finding this gremlin!
@AlmightyAdan , sorry to hear about your electrical issues. I don’t think I have ever had to replace a fuse since I have had my LJ. That said, PO did a hack job on the radio install. I would probably inspect that first. Any other hot leads coming off the battery terminal?
It is very common to have to replace the external Voltage Regulator with these older LJs. I also replaced my ignition harness, as the PO had an alarm system and several splices under the steering column. There is a Heating Element on the passenger side firewall area that I replaced as well.
Those are just a couple items / areas I would check and inspect based on my experience.
It is very common to have to replace the external Voltage Regulator with these older LJs. I also replaced my ignition harness, as the PO had an alarm system and several splices under the steering column. There is a Heating Element on the passenger side firewall area that I replaced as well.
Those are just a couple items / areas I would check and inspect based on my experience.
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Only a few circuits are connected directly to the battery (not switched, e.g. by the ignition switch). These include the live feed to the ignition (solid black wire), the clock and radio constant feeds, the HAZ-HORN circuit and the alternator wiring, among others. Look for shoddy modifications, e.g. stereo or immobiliser, aftermarket horns etc.
Obviously, any non factory wiring attached directly to the battery positive terminal(s) is a prime suspect.
Obviously, any non factory wiring attached directly to the battery positive terminal(s) is a prime suspect.
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Were you able to download that wiring manual? It won't be exact for your LJ79 but will be a good starting point. Lots of good info online about hunting down parasitic drain on automotive electrical systems, too. You'll want a good multimeter.
Also, pretty sure an LJ79 will have an internally regulated alternator and not an external voltage regulator. There should be several fusible links coming off the positive battery terminal, you'll want to check those too.
Also, pretty sure an LJ79 will have an internally regulated alternator and not an external voltage regulator. There should be several fusible links coming off the positive battery terminal, you'll want to check those too.
- Thread starter
- #6
Wish it was this easy with this one, the Prejvous owner for some reason had the fuse box removed. There is no engine bay fuse box. The wiring is so shoddy tracing it and knowing what’s what is impossible! But I appreciate the helpDo you have a multimeter? The fastest way to find what part of the wiring is drawing power is to use a multimeter and watch the amperage drop to zero when you remove the correct fuse. Then you can check just that section of the wiring harness and find the culprit. It usually comes down to a PO DIY fix or mod (likely stereo related)
Google "finding a parasitic power drain on a vehicle" and that should point you to a good how-to with a multimeter. Best of luck finding this gremlin!
- Thread starter
- #7
Where do you find the wiring manual for this Prado?
My apologies, I was confusing you with another person who recently was working on electrical problems in an LJ79. Here is the link: Wiring diagrams for 1992 Prado - https://forum.ih8mud.com/threads/wiring-diagrams-for-1992-prado.1219181/post-13241625
by far the best way!Do you have a multimeter? The fastest way to find what part of the wiring is drawing power is to use a multimeter and watch the amperage drop to zero when you remove the correct fuse. Then you can check just that section of the wiring harness and find the culprit. It usually comes down to a PO DIY fix or mod (likely stereo related)
Google "finding a parasitic power drain on a vehicle" and that should point you to a good how-to with a multimeter. Best of luck finding this gremlin!
bro, my rig also did not have a fuse box in the engine bay. all the relays are dangling. i had a similar sort of issue. the culprit was the dashboard clock. the issue was still there. I removed the battery, slowly charged it, and then reinstalled it. Since removing the dashboard clock connectors, it has been working fine till now.
I'm hoping the previous owner at least left you the fuse box inside the cab. I bought a cheap little tool from Harbour Freight to chase down electrical drains. It plugs in to where the fuse goes for that circuit and should tell you the amperage draw. It will at least point you in the right direction of what circuit is draining the battery. It is essentially a multimeter in a convenient little package. https://www.harborfreight.com/30-amp-fuse-slot-circuit-amperage-draw-measurement-tool-70079.html
