I have had an on going electrical issue with my 1995 4Runner 3.0 SR5 that some of you have experienced as well.
This thread sums up the issue and you will notice that I posted to it and thought my problem was fixed....then it came back as it did for some others in that thread. I finally found the root cause and two methods to fix it.

I have a write up done (no pictures yet) but it's too long to post in here so I will summarize the whole thing for you guys.

Symptoms:
- Radio whine through the speakers (sounds like an alternator whine) with the AC turned on
- When pressing on the brake pedal the volt meter drops dramatically but briefly and if the headlights are on they will noticeably dim or flicker
- When using the turn signals the voltage drops dramatically but briefly
- When using the headlights or flash-to-pass high beams the voltages drops dramatically but briefly
- When attempting to start the vehicle the volt meter may read *very* low (~9V) and the vehicle will not turn over and all accessories barely function. After many attempts at turning key the voltage will return to normal and the vehicle will start as normal.

During any of the above situations it the radio may turn off for a few seconds and the engine may even stall out briefly (!) and that will scare the crap out of you the first time you have it happen to you @ 70 MPH in traffic.

The frustrating part of all this is everything points to a bad ground situation...but it isn't in this case. The other odd thing is due to the slight movement of the cable as you drive over bumps and such the problem may be intermittent.

The problem:
It turns out to be a combination of the factory crimp and too small of a cable gage on the cable that runs from the POS terminal on the battery and goes to the main relay box. This cable attach's to the "slow blow" fuse inside the relay box. This crimp gets weak with normal removal of the battery cables over time. This cable may also begin to heat up and contribute to the situation as well do to the small gage of the cable. If you think this may be your problem you can try tightening up the factory crimp to see if anything gets better. You should verify all your grounds are clean and tight as well as the battery is in tip top shape first.


The fix:
I found two possible methods for this
1) Solder the factory crimp on the battery side of the cable
-or-
2) Replace the cable with a thicker gage cable and solder both ends and replace the factory cable. I did the cable replacement method to kill two birds with one stone.

Identifying the cable
The cable in question runs from the POS battery terminal to the relay box just a few inches away and inside there is the 'slow blow' fuse assembly. The wire attach's to the bottom side of that fuse. The whole fuse assembly will slide out of the bottom of the relay box once you get the relay box off the factory mounts and turned so you can remove the bottom. The factory cable is crimped and soldered on the relay box side so you will have to cut the crimp off if you are going to replace the cable and use on of the screw terminals on that same side to hold the new cable. Its a tight fit this way but it does work.

Modifications
I modified a 19" 6 ga. battery cable from Autozone that had a battery post clamp on one end and a flat terminal with a round hole through it on the other end. I just cut of the battery post clamp end, measuring the length I needed for the new cable (about 10") and soldered on a 6 ga. ring terminal. Then it was just a matter of adding heat shrink and the factory insulation sheath from the original cable to the new cable. Then I used this new cable to replace the factory cable that attach's to the underside of the 'slow blow' fuse assembly in the main relay box. The original flat terminal end on the new cable (the one I didn't cut off the new cable) gets attached to the POS battery clamp just where the factory one connected.

Prices
Since I didn't want to modify my factory part initially, I went to a salvage yard and pulled the factory slow blow fuse assembly and the factory cable for my test modifications.
My total costs were:

19" 6 ga. replacement battery cable (red) - $2.69 @ Autozone
6 ga. ring terminal (3 pack) - $1.99 @ Home Depot
3/8" Heat shrink tubing - $1.99 @ Home Depot
Salvage yard donor parts - $10.00 @ Toyota Heaven

Toyota only sells this cable if you buy the entire POS cable assembly and my local stealership quoted me $137.00 for the POS battery cable assembly complete with the suspect crimp that causes the problem in the first place.

Notes
That should be plenty of info to get you going if you are here searching for a fix. The write up is lengthy and detailed and I don't have pics just yet (or hosting) but if you want it send me a PM and I will email it to you in Word .DOC format. My research turned up the following sites that led to this fix:
Google Groups
www.yotarepair.com (see the section labled 95 4Runner V6 with electrical problem)

Hope this helps somebody because if you have this problem it will drive you nuts.

 

I know you guys aren't gonna believe me but after driving around with this new 6 ga. wire I can really tell a difference. The original problem is gone of course but I have also noticed a improvement in acceleration in the 0-40 range. Makes sense really - this is the primary electrical feed for damn near every thing and a bigger wire helps the electricity flow more efficiently.

I doubt this is 'new' power but rather re-gained power that was previously lost due to the bad wire. Either way it is a noticeable improvement in acceleration and overall smoothness of operation. Not to mention that turning on any electrical accessories hardly makes the volt meter move at all now - even with everything turned on.

 

Here are some pics that should help understand just what was done and how it goes together

Here is an over view of the parts:



Here is where everything is located under the hood:



Here is what it all looks like with the sub assembly ready for reinstallation:




It's all very easy to do once you realize there is room to attach the ring terminal to the bolt holding the fuse in place.

 

Thanks! I will definetly do this mod this summer!

 

This helps to provide a slight amount of voltage and helps with the drop you experience when increasing the load on your elec. system, but it does not completely eliminate the problem. I'm going to check all of the other grounds and see if I can correct the problem completely.

 

Good luck Rasta!

So far so good for me and this fix. It's been about 2.5 months and none of my problems have returned at all. For me this did indeed fix the issue.

One other thing I did do after the above fix was to upgrade the "big three" wires in the engine compartment - search for 'big 3' and you should find the link to it. Basically its an upgrade of the battery neg. to chassis ground, engine to ground and alternator positive to battery positive.

 

Wow! I must admit that this actually did correct my problem almost completely. In my last reply I reffered to the problem still existing, but today I took her for a spin and the dimming of my lights is vitually unnoticeable and the radio does not cut out or struggle at all. Even after adding an amplifier and XM receiver tto the mix. I also upgraded the ground from the negative terminal. Great Mod! I retract my previous doubts! Thanks!

 

Congrats!!

I think there was a serious design flaw in the implementation of this 'slow blow' fuse wire in 1995 and maybe all 3.0 - it seems the wire was 'just enough' to work when new but down the road a few miles and a battery change or two latter, it just isn't up to snuff any more. I am no electrician at all but it sure seems the resistance of this wire builds up to the point where it behaves like a bad ground situation...that has got to be some serious resistance to do that I would think...but then again I-A-N-A-EE

One other crazy thing I will mention is that I also switched from the original battery post clamp to a Autozone brass clamp (as seen in the pics above) and was able to feel a difference as well. Again, probably not new power but none the less the low end, part throttle acceleration was a bit smoother that with the sheet metal clamp the factory provides.

Glad all is working well for you!! Help me spread the word a bit - this is an easy fix and I think there are *a lot* of 3.0 owners out there suffering needlessly

 

I'm going to give the brass clamp a try as well. maybe this weekend. I've been waiting to find someone with a 2nd Gen. 3.0 so I could lay a little knowledge on them. Ther firs person I see will have the info. passed on to them!

By the way, I work a little with electronics on F-15s and I agree that there must be a considerable amount of resistance in the old factory wire. Over time heat and corrosion can easily incrase the amount of resistance in a wire. I'm willing to bet the problem is exactly where you described...in the crimp.

 

So about the radio, mine will shut off for a couple of seconds then turn back on every once in awhile. It does this most of the time when i touch something on the receiver like the volume knob or something. Is this kinda what you experienced?

 

yotafool - my problem first manifested itself with the headlights blinking or flickering when I stepped on the brakes, and then it spread to anything electrical adding to the problem. I had whine through the speakers only with the AC on for awhile...then the high-beams started to stall the engine while at speed...then the radio would cut on and off anytime *any* extra load was introduced...then it became hard to get it started. I don't mean it was hard to get it to turn over I mean I would roll the key forward and I would barely have 9 volts on the meter.....if I rolled the key back and forth many times it would eventually jump back to >14 volts like all was fine and then start up just fine.

Any and all of those things can easily look like other problems - normally they would be but this wire seems to be the cause of a lot of odd electrical problems with the 2nd gen 3.0's.

It only cost about 5 bucks and maybe takes a total of an hour to do - it wont hurt anything to do it if you don't need it. If your symptoms are close to similar and you have already checked out bad/loose grounds and the like....give this a shot - its cheap and easy!

Rasta - Thanks for the feedback and the conformation - I started out as parachute infantry in the Army @ Ft.Bragg back in the day but now I am old(er) and slow(er)... Hey if you do the Autozone brass clamp, watch out for tight clearances between the stud and the hood. I was worried so I measured and cut it flush with the nut after the slow blow fuse wire was attached. The problem with the Autozone brass clamps is they molded the little arms on the wrong end of the taper of the post clamp for the best hood clearances. Mine has been on since I wrote that first post and no problems although I do make sure the factory boot is always over the + clamp anytime I am shutting the hood (I am paranoid at times). I did try 'flipping' the clamp but I could not overcome the taper being the wrong way for the post..if you could drill it out some it would probably work but I dont have a bit that big.

 

Nice to see my post helped and great writeup ROMAD!

 

Romad- Nice to meet a fellow military man on the site! I'm sure there are others lurking around. I haven't had the chance to do the brass clamp upgrade yet but thanks for the advice. Hope to do it soon.

 

So, when I do this mod, do I need to go to the junkyard and pull another box as well, or was it just to test out the original thought??

AFAIKT, I just need to get the cable itself and rig it up???

Mike

 

I went to the junkyard today looking for stuff for the runner when i remebered about the electrical mod. Saw this wrecked runner with no engine but the wires from the battery to the starter where there. So i grabbed the wires and was only charged $3. When I got home i statred working wire upgrade and noticed that the wire from the batt to the 80amp fuse was 2 different guages. About 3 inces from the battery was the splice. Not sure if this is an OEM thing or a fix from previeous owner.

 

I just did this mod on my '85 Toy 4Runner Wednesday night. I found the original 8 ga wire spliced (badly) into a 14 ga wire that went to the POS terminal of the battery. I replaced it with a 4 ga wire from Autozone.

I've got pics of the "wire from heck" if anyone can post them for me.

Thanks,

Albin

 

Man, I did this about a month ago now and as far as I can tell it has made a huge difference. Lots more power bottom end and more pickup.

I dont understand the mechanics behind this but why would it do that? It's an electrical modification. I figured it would remedy any loss I knew I was getting in the electrical system but I didnt think it would be a performance mod at all.

Mike

 

Are you a USAF ROMAD?

 

Just want to clarify something. Did you replace the old wire (white) with the new wire (red 6 ga.) that you soldered the ring clamp on? Why did you clip crimp off as opposed to just connecting the new ring clamp directly to the fuse box? Does using a larger gauge wire defeat the intended slow-blow feature of the original wire?
Thanks for the write-up.

Just re-read the instructions. Think I understand it now. Replace old wire with modified new wire. Hope this works!

 

Sorry for not getting back sooner guys - I have been away from the boards for a long time. Glad to see some of you have been trying this out - my problems have not come back since I did this mod and my electrical system is as strong as ever now.


No junkyard parts are really needed at all. I wasn't sure how well I could do this the first time, or if would even work - so I pulled the affected parts from the yard to "test" with. Now that I know it works there isn't any need for the extra parts unless you too want to keep the factory ones "just in case"


Same thing here - I was surprised by the difference too. Best I can figure out is that the fuel injection and the ignition system are getting 'more better' juice and things are working more efficiently.


Nope, former US ARMY that used to work with TACP on occasion and had a few buds that were ROMADs


Yes


It was too big to fit the clearances in the box and I was wanting to replace the smaller white wire with the larger red wire. I also needed to maintain the brass plate to conduct electricity to the other connections on the slow blow fuse box (with out the brass plate you would isolate the other connections)


My understanding is the "slow blow" portion is the fuse you are attaching the wires too. I don't think the original wire has any slow blow ability at all as it was a single piece of 10 gage(?) wire (white wire as seen in pics)

My 1995 3.0 did not have a fusible link on the wire at all but many of the ones in the junkyard did though. Not sure why some have this and some don't.