khoopes

I have an 87 Turbo 4Runner that has the digital dash cluster. Well, every time I turn on the headlights, the dash starts intermittently going out. I notice that when the problem happens it seems to make a difference where my gauge light adjustment knob is positioned, i.e. it goes from on to off very fast instead of using the whole range. When the problem happens I cannot roll down the back window either. And if I turn off the headlights then poof! Everything works again.

I had trouble yesterday morning with the alternator not charging, but after tinkering with the dash cluster- removing it for cleaning the glass, The alternator was charging again. I don't know if the two are related. This must have been an ongoing problem for the PO because the put an aftermarket switch on the back window. The PO said he put a new alternator on it but the battery was stone dead when I bought it from him as it had been sitting. I have a different battery in now.

Thanks for any sugeestions. I have a pdf 88 FSM but not an 87.

ozziesironmanoffroad

sounds like a bad ground...

Matt16

Or alternator. Chances are the brushes are going on the alternator. Once it starts going, you have maybe 50 miles before it dies. The brushes are cheap and easy to replace.

Search "weird electrical problem". I mean it, people ALWAYS describe it the same.

khoopes

Interesting. Yesterday I drove it about 250 miles and it starting blinking out without the headlights on. I troubleshot it at the parts store for a while, found that the junction point from the alternator to the battery point had been overheating so I cut the wires and put new connectors at the junction point. Didn't fix the problem but one less issue... found a coolant leak while scouring over the wiring where someone didn't put the clamp back on a little hose under the intake manifold. I also discovered someone has taken the plenum off and did not route the harness correctly through after putting it back on so all the sensors have the wires pulled really tight.

I think I will go for a new battery and alternator. Has anyone had good luck with aftermarket alternators or should I get a Toyota reman? It is $175 bucks.

One more thing, the dash still blinks out when the alternator is disconnected. IT is like any time I roll a window or any kind of electrical load.. or when driving normal with nothing on and battery disconnected. I also note that the voltages on the fuse box seem like they are not stable, like I have resistance in the wiring or something.

just a 22re

if the volts are jumping around like you said try looking at the batter connectors they might be losse or bad and also check the alt wires and if you said the harness is all messed up then the motor might not have a grond anymore try taking a 4g wire to the head and right to the neg side of the battery cheaper then a battery and alt cause there good

battery lets you start in the moring and driving with the battery disconected tells you the alt is good

khoopes

More on this. I found the Fluke 77 I have has unreliable connections on the leads. I have recently changed the leads to new ones and thought that fixed it but apperently it is internal in the meter. So I am not sure how accurate my readings have been. Anyway, the tailgate window relay circuit and the digital cluster are on the same bus (E bus on the schematic) which comes from one side of the ignition switch. I spent several hours troubleshooting my rear window not working from the key switch in the back door. The key switch power comes right off a circuit breaker to the window relay, but the front switch circuit gets power to the relay through the engine fuse and the E bus. I found that the wiring harness below the vehicle rear that feeds into the back door had gotten water into the wires and corroded the wires in two although the damage was not evident to the eye. I removed the harness, found the trouble spots, and rewired it. Re installed it and now my back window works fromt he key switch--- and I discovered that often the switch that senses the back door is closed does not function properly, and that is why the it appears the back window does not work, I think it is unrelated to the gauge cluster problem even thought they both obtain power form the engine fuse rail. I can not find a schematic for the digital gauge cluster and the non digital cluster only takes one power feed from the engine fuse, but I think the digital cluster takes two feeds from it. I have watched the power feeding the cluster remain steady but the display go out, running but with no alternator installed at all. I think the cluster itself has an internal problem. Now if I could find a schematic for it I will disassemble it and try to determine what is wrong.

mnmontana

I believe the back window, and the interior lights share a ground. Ceck the manuel, but yeah... bad ground is what id suspect