87 4Runner SR5 Turbo - Headlights go on, Dash/Interior Lights go off - YotaTech Forums



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87 4Runner SR5 Turbo - Headlights go on, Dash/Interior Lights go off

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Old 10-18-2017, 07:33 AM   #1
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87 4Runner SR5 Turbo - Headlights go on, Dash/Interior Lights go off

I just picked up my '87 SR5 22rte 4Runner from FL last weekend. All the interior lights and digital dash features work great in the day, but when I turned the lights on everything but the ETC light on the dash, Indicator Lights (Brake, etc) and Digital Clock goes dark. I immediately thought there must be something wrong with the dimmer - maybe it's stuck in full dim mode - so I pulled it last night and it's circuit board looks okay, but I don't know enough about them to tell.

Also, from my searches, I've seen issues where a fuse or trailer wiring causes this problem but it's always in conjunction with tail lights being out. My tali lights work fine with lights on or brakes pressed.

Help?
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Old 10-18-2017, 09:35 AM   #2
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Got a multi-meter? If not, spend $6 at Harbor Freight.

Without a multi-meter, senses would suffice...
Find the tail light relay (location here: https://www.yotatech.com/forums/f116.../#post52364207)
Feel/listen to click when you turn on tail lights. That click is contact closing to turn on tail lights.
Turn on head lights. The tail light relay should NOT click. If it clicks and tails and dash lights go out, that means the relay contact opened when it was not supposed to. Suspect a bad contact in dimmer combo stalk switch.
With headlight still on, jump pin 11 (red wire with black stripe) to pin 10 (white with blk stripe = ground) of dimmer combo switch . Does tail light relay click and dash lights come back on? If yes, check/clean contacts. IIRC, Terrys87 has that procedure.

When you have your multi-meter, check these voltages...

Last edited by RAD4Runner; 10-18-2017 at 09:46 AM.
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Old 10-18-2017, 09:50 AM   #3
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Perfect - I've got a MM (from HF) and will test those voltages this afternoon. I'll be back in touch with what I find.

Thank you!
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Old 10-18-2017, 11:40 AM   #4
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The clock is attached to the dimmer also, so if it works as expected when you turn the dimmer its not likely a problem there.

The problem with the digital dash is a side effect of its coolness factor, it uses high voltage displays (vacuum tubes) for most of the instruments. It is susceptible to "brown out", a low power situation (voltage and or current).

Start with testing battery voltage in the following states, ignition off, engine running at idle with running lights off, running lights on, and finally headlights on. Repeat measurements at the digital cluster main power input with the cluster disconnected.

​​​​​​​While you have the dash apart verify the (few) screws are tight against the flexible circuit material and there is not a bunch of surface corrosion on the flexible circuit terminals.

Short of finding a problem there (bad flakey wire, or connections) it's going to be internal to the cluster. I haven't yet found the time to pull mine back out and inspect for replaceable components. It could be something simple like a failing capacitor or a failing solder joint.
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Old 10-18-2017, 11:44 AM   #5
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Originally Posted by RAD4Runner View Post
Got a multi-meter? If not, spend $6 at Harbor Freight.

Without a multi-meter, senses would suffice...
Find the tail light relay (location here: https://www.yotatech.com/forums/f116.../#post52364207)
Feel/listen to click when you turn on tail lights. That click is contact closing to turn on tail lights.
Turn on head lights. The tail light relay should NOT click. If it clicks and tails and dash lights go out, that means the relay contact opened when it was not supposed to. Suspect a bad contact in dimmer combo stalk switch.
With headlight still on, jump pin 11 (red wire with black stripe) to pin 10 (white with blk stripe = ground) of dimmer combo switch . Does tail light relay click and dash lights come back on? If yes, check/clean contacts. IIRC, Terrys87 has that procedure.

When you have your multi-meter, check these voltages...
Iím pressing the brake to ďturn the tail lights onĒ, but cannot hear/feel the contact moving in the tail light relay. I just removed it and am going to inspect it next.
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Old 10-18-2017, 11:46 AM   #6
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The clock is attached to the dimmer also, so if it works as expected when you turn the dimmer its not likely a problem there.

The problem with the digital dash is a side effect of its coolness factor, it uses high voltage displays (vacuum tubes) for most of the instruments. It is susceptible to "brown out", a low power situation (voltage and or current).

Start with testing battery voltage in the following states, ignition off, engine running at idle with running lights off, running lights on, and finally headlights on. Repeat measurements at the digital cluster main power input with the cluster disconnected.

While you have the dash apart verify the (few) screws are tight against the flexible circuit material and there is not a bunch of surface corrosion on the flexible circuit terminals.

Short of finding a problem there (bad flakey wire, or connections) it's going to be internal to the cluster. I haven't yet found the time to pull mine back out and inspect for replaceable components. It could be something simple like a failing capacitor or a failing solder joint.
Note that the clock does not dim when I turn the dimmer. It simply stays the same brightness regardless of what I do with the dimmer. And all dash lights work fine with the lights off.

Also, the backlight behind the SR5 gauges, A/C and Heat controls, and all other interior lights go off with the lights on too so I highly doubt itís just something to do with the digital dash.
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Old 10-18-2017, 11:50 AM   #7
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Iím pressing the brake to ďturn the tail lights onĒ, but cannot hear/feel the contact moving in the tail light relay. I just removed it and am going to inspect it next.
Tail lights and brake lights are not the same. There is no brake light relay. Tail lights are turned on with the "headlight" switch.
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Old 10-18-2017, 12:29 PM   #8
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Tail lights and brake lights are not the same. There is no brake light relay. Tail lights are turned on with the "headlight" switch.
Thanks. Iím just turning headlight switch to driving lights and not headlights. No movement in the tail light relay and itís cold vs the EFI relay which is hot to the touch. Iím guessing itís the relay...
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Old 10-18-2017, 01:33 PM   #9
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Ok, just picked up a new Tail Light Relay. Now the relay “clicks” when I turn on tail lights, but doesn’t click when I turn on the headlights. If I understand correctly, the relay is now working.

Unfortunately no change to the dash dash or other interior lights - still off when either tail lights or headlight are on.

Also, the digital clock dims when I turn either tail or headlight on, but has no reaction to the dimmer switch. The dimmer also looks like it’s either old or was burned (is Yellow overall but dark brown in areas). Think I should replace the dimmer? Or can I bypass it to test it somehow before buying s new one?
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Old 10-18-2017, 10:17 PM   #10
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Sorry I was confused... I overlooked Digital dash!

A problem well-stated is a problem almost solved.

O.P. please re state the problem using clearer terminology... For the people who are a thousand miles away
(i.e., don't just say "interior lights because that includes dome lights).

Digital Dash Display/gage Light, LED bars, etc - that, I would expect, come on as soon as ignition OR accessory is turned on. Like Co_ mentions above, clock comes on with the digital dash. I know is that there is a DIM function where the digital clock dims when taillights or headlights are turned on. Based on what CO is saying this may also affect the digital dash display. Sorry I do not know the circuit that controls that dim function.

Running Lights - (steady red lights in rear corners, steady amber in front corners) that come on when the headlight dimmer-combo switch is on first on position. That's when the tail light relay clicks to close contact.

Dash backlighting. Comes on with the running lights. However, this is controlled by the analog / potentiometer dimmer - like a volume control. Different from the auto-dim function of the digital dash and the clock.

Headlights - On when dimmer combo switch is in second ON position... I thought O.P. meant to say that when he turned the headlights on the "running lights" turned off (that's why I suggested to observe the tail light relay if it was clicking for the second time when headlights were turned on - that suggests bad switch contacts.)
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Old 10-19-2017, 12:21 AM   #11
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Stupid browser ate my post...


Light control switch should have continuity between pins 10(gnd) and 11(tail) in both "on" position. Sounds like you are good there.

you can jumper over the rheostat to put the lights to full brightness.

Rad was right, check for voltage on both sides of the tail fuse.
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Old 10-19-2017, 05:58 AM   #12
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A problem well-stated is a problem almost solved.

O.P. please re state the problem using clearer terminology... For the people who are a thousand miles away
(i.e., don't just say "interior lights because that includes dome lights).
Great idea. Also, I love '80s Toyotas but am much more Mechanically inclined than Electrically inclined. As other members said, I need to get "great" with a multi-meter. This is a good project to practice on.

Problem Well Stated: All interior and exterior lighting works fine with Running Lights (light switch turned on one position) and Headlights (light switch turned fully on - two position). When I turn Running Lights or Headlights on, the:
a) Digital Dash goes out except ETC light and Indicator Lights (Check Engine, Brake, AT Temp, etc)
b) Heat / AC backlight goes out
c) SR5 Altimiter / Inclinimeter backlight goes out
d) Digital clock dims, but does not go out
e) Aftermarket stereo (which looks like a recent add by PO) stays on fully light regardless of running or headlights on/off
f) With Running or Headlights on, the dimmer switch has no effect on any lights
g) All exterior lights work fine as they should: Running Lights turn on front running lights and rear tail lights; Headlights turns on front running lights, front headlights, and tail lights

I read for an hour last night. Next steps are:
1) Bypass dimmer using this description:
"To do this, you just unplug the dimmer switch and use a paperclip to "jump", or connect, the positive and negative. Be careful here though: The plug coming FROM behind the dash that plugs into the Rheostat housing (knob on your dash) has 3 prongs. 2 prongs provide power (positive) and one is negative. You have to jump the 2 prongs that are over and under each other, or parallel. These will be a positive and negative that you are jumping. The other is off to the side and is facing a different direction (sort of up and down). Leave that one alone."

https://www.yotatech.com/forums/f116...y-help-183722/

2) Check voltage on each side of 15 amp Tail/Dimmer fuse in drive kick-panel (note I already put a new 15amp fuse in there) per description above.

3) Check aftermarket stereo wiring - looks like a mess back there.
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Old 10-19-2017, 09:11 PM   #13
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Great idea. Also, I love '80s Toyotas but am much more Mechanically inclined than Electrically inclined. As other members said, I need to get "great" with a multi-meter. This is a good project to practice on.
Awesome. We'll help you with that. You see, with mechanical issues the senses (sight, smell, touch) are usually enough to expose the problem. With electrical, we need to see the electrons run - with the volt meter. Well... we can smell smoke, too, but then that would be too late - LOL!

Tnx for the clearer description below... Best if we could see the schematic, then we can group circuits that behave in same manner and look for point common to them where they get power. Anyway... Please see my notes in lime below.

All interior and exterior lighting works fine with Running Lights (light switch turned on one position) and Headlights (light switch turned fully on - two position).

IMPORTANT QUESTION:
Are there any lights on the dash (or center console near sifter) that are off when running light switch is off, and come on only when running light switch is turned on?


When I turn Running Lights or Headlights on, the:
a) Digital Dash goes out except ETC light and Indicator Lights (Check Engine, Brake, AT Temp, etc) -
This Digital Dash going out is the work of the auto-dim system. Either it is over-active/broken or setting is wrong.
Combination meter / indicator gages take their power from engine fuse so not affected by light control. They turn on when Ignition is on:
schematic is here

b) Heat / AC backlight goes out, c) SR5 Altimiter / Inclinimeter backlight goes out
Need to see schematic IF these are controlled by digital dash auto-dim. On the non-turbo these run off the running lights circuit (see above post)

d) Digital clock dims, but does not go out -
This auto-dim happens on DLX trim as well. This is normal. This happens at same time as digital dash dim but has separate control (clock schematic here).

f) With Running or Headlights on, the dimmer switch has no effect on any lights.
By "dimmer switch" do you mean the dimmer "rheostat" that you turn like a volume control correct?

g) All exterior lights work fine as they should: Running Lights turn on front running lights and rear tail lights; Headlights turns on front running lights, front headlights, and tail lights.
Good, so apparently no issue with the dimmer-switch combo.

I read for an hour last night. Next steps are:
1) Bypass dimmer using this description:
"To do this, you just unplug the dimmer switch and use a paperclip to "jump", or connect, the positive and negative. Be careful here though: The plug coming FROM behind the dash that plugs into the Rheostat housing (knob on your dash) has 3 prongs. 2 prongs provide power (positive) and one is negative. You have to jump the 2 prongs that are over and under each other, or parallel. These will be a positive and negative that you are jumping. The other is off to the side and is facing a different direction (sort of up and down). Leave that one alone."

https://www.yotatech.com/forums/f116...y-help-183722/

2) Check voltage on each side of 15 amp Tail/Dimmer fuse in drive kick-panel (note I already put a new 15amp fuse in there) per description above.


e) Aftermarket stereo (which looks like a recent add by PO) stays on fully light regardless of running or headlights on/off - Typical of after-market stereos. Probably not related to the digital light off issue.
3) Check aftermarket stereo wiring - looks like a mess back there. - Don't worry about that yet, although that mess could be part of previous owner hacking the wiring.


Last edited by RAD4Runner; 10-20-2017 at 09:50 AM.
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Old 10-19-2017, 10:42 PM   #14
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b) Heat / AC backlight goes out, c) SR5 Altimiter / Inclinimeter backlight goes out
Need to see schematic IF these are controlled by digital dash auto-dim.
I just want to confirm that the Heat / AC backlight never turns on, regardless of the running lights and headlights being on or off.

Is this correct?

I know on my truck that the Heat / AC backlight only comes on when the running lights or headlights turn on.

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Old 10-20-2017, 07:14 AM   #15
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IMPORTANT QUESTION:
Are there any lights on the dash (or center console near sifter) that are off when running light switch is off, and come on only when running light switch is turned on, and stay on when headlights are turned on?
No, other than the clock (bright when all off, dim when running or headlights on) and radio, absolutely no lights on the dash or center console near shifter come on in any position.
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Old 10-20-2017, 07:15 AM   #16
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I just want to confirm that the Heat / AC backlight never turns on, regardless of the running lights and headlights being on or off.
Is this correct?
Yes, that is correct.
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Old 10-20-2017, 11:39 AM   #17
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I just want to confirm that the Heat / AC backlight never turns on, regardless of the running lights and headlights being on or off.
Is this correct? I know on my truck that the Heat / AC backlight only comes on when the running lights or headlights turn on.
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Yes, that is correct.
But, P.O. says^^^ "When I turn Running Lights or Headlights on, the: a) Digital Dash goes out... b) Heat / AC backlight goes out... c) SR5 Altimiter / Inclinimeter backlight goes out"
This implies that when ignition is on, BEFORE running lights are on, the DD, Heat/AC backlight and SR5 backlight are on. THEN they go out when running lights are turned on.
IF things are as O.P. describes them above, then the above are controlled by auto-dim of the digital dash.

With no light turning on when running light is turned on (first on position), This suggests that the dimmer rheostat (that turns like a volume control) could be bad / open.

Charles4x4,
Does your dimer rheostat have only 2 pins as in schematic below?


dash backlight dimmer circuit:
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Old 10-20-2017, 11:43 AM   #18
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Please post video

Looks like we have two root causes here:
1) Over-active/wrong setting/ broken digital dash auto-dim, AND
2) Bad/ most likely open dash backlight dimmer rheostat.

A picture paints a thousand words; a video a million words

Charles4x4,
Please post video showing the dash lights / gage lights from ignition OFF, but turning running lights on to first position, then to headlight second at position.
All OFF. Then accessory on, ignition on, start, running light first on position, then headlights a second on position.

When you're ready to put multi-meter to the rheostat, let us know, too.
Also post picture of your rheostat.

Last edited by RAD4Runner; 10-20-2017 at 11:46 AM.
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Old 10-20-2017, 01:31 PM   #19
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so you bought another 87 Turbo or is this the same one you had for sale during the summer?
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Old 10-20-2017, 04:02 PM   #20
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so you bought another 87 Turbo or is this the same one you had for sale during the summer?
just got this one last Friday!
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