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Dashboard lights and rheostat not working?

Tiny
BUTYDUDE
  • MEMBER
  • 1991 TOYOTA CAMRY
  • 2.5L
  • V6
  • AUTOMATIC
  • 125,000 MILES
I have a lighting problem.

When you turn the headlights on, the lights on the instruments in your car should get dimmer (clock, ac, gauges). However, after installing an aftermarket stereo, when turning headlights on the dim lights behind the gauges (speedometer, fuel, etc.) Do not turn on, and the rheostat does not work at all.

It couldn’t be the wiring from the stereo (at least I believe) because all illumination lights to the instruments are run parallel to each other, so the fact that the radio is disconnected shouldn’t affect anything else.

I blew two different fuses during the installation of the radio, due to an unfortunate mistake. It was the 20A Dome, in the engine fuse box, and the 15A tail, in the left side kick panel.

I am wondering if I damaged some other electrical components, but I have no idea which ones. All fuses are fine.
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Sunday, February 4th, 2024 AT 5:33 PM

7 Replies

Tiny
BORIS K
  • MECHANIC
  • 762 POSTS
Hello,

As you have fitted an aftermarket radio, I would suggest checking the wiring at the original connector.

The green wire at either pin 2 or 10 was switched out to white/green wire at either pin 5 or 12 depending on if you had a separate or build in amplifier.
The green wire supplies 12V to the radio and the radio then switches it out to the white/green wire to a junction behind the right side of the dashboard.
This junction then supplies the rheostat on a black wire at pin 2.
You could simply bridge or join the green and white/green wire at the original radio connector.

See diagram below.

The 12V is supplied by the taillight relay to the panel fuse (7.5A) in the instrument panel junction box, see 2nd diagram below.

Cheers, Boris
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Monday, February 5th, 2024 AT 8:04 AM
Tiny
BUTYDUDE
  • MEMBER
  • 5 POSTS
Boris,

Firstly, thank you for the quick response.

I did as you said, connected green to white/green, and nothing changed. The blue/yellow provides constant 12V from the battery to the radio, and the grey gives 12V power to the radio from the ignition switch. So, should I connect the white/green to one of those? Or if the green should be connected to the white/green, what’s next?

I’ve attached some pictures below.
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Monday, February 5th, 2024 AT 1:51 PM
Tiny
BUTYDUDE
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  • 5 POSTS
This is the wiring diagram I have been using:
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Monday, February 5th, 2024 AT 1:56 PM
Tiny
BUTYDUDE
  • MEMBER
  • 5 POSTS
Just checked with voltmeter, 12V is coming through each wire.
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Monday, February 5th, 2024 AT 2:21 PM
Tiny
BORIS K
  • MECHANIC
  • 762 POSTS
Hello,

It appears that my wiring information is different to yours.
Let's work with your information.
Suggest checking at the rheostat next.
Pin 1, green wire should have 12V with ignition on, lights on.
Pin 2, white/black wire should be ground.
Pin 3, black wire should have 12V with ignition on, lights on.
This 12V comes from the combination meter, in at pin 2(green wire and out at pin 1(black wire).

12V supply is from tail lamp fuse (15A), supplied by the taillight relay.
Are the taillights working?
Is the glove box light working?

Cheers, Boris
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Tuesday, February 6th, 2024 AT 2:35 AM
Tiny
BUTYDUDE
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  • 5 POSTS
Hi,

Taillights work.

At the rheostat and behind the instrument panel (comb. Meter), the green wire does not supply 12V power with lights on.

The glove box light works (with the lights on, the light inside glove box turns on when glove box is opened).

The other thing on that circuit, ECT switch, also works.

It is just at the rheostat and the comb meter that the lights do not work and the green wire does not supply 12V.

I am thinking that the problem has to be between the oval 1F and the start of the green wire (at various locations). The green wire coming off the 15A going sideways works perfectly normal. So between the 15A and the start of the green wire, or somewhere at the very end of the circuit, there is a problem, maybe with a box being unplugged, or with a specific wire, or a circuit breaker.
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Tuesday, February 6th, 2024 AT 6:25 AM
Tiny
BORIS K
  • MECHANIC
  • 762 POSTS
Hello,

Have you tried supplying a separate 12V to the green wire at pin 1 of the rheostat?
If the lights work, then I would suggest to perhaps run a wire from the glove box green wire to pin 1 at the rheostat.

Cheers, Boris
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Wednesday, February 7th, 2024 AT 5:59 AM

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