Dimmer Repair for 95 Mitsubushi Montero (Pajero/Shogun if you are UK)

[ricardohd91]

I have a 1995 Montero/Pajero with a non functioning instrument panel dimmer. Part is discontinued and not available anywhere anymore, used ones from bone yards have all been duds. So I ask here. I have seen Dave's videos for a while now and now its my turn to try a repair of a board. The board uses a 12 volt input, a ground, and a output. From what little i know, i can make out a potentiometer, something that i think is a ceramic load (labeled  Micron 47T) there is one 50v 1 uf cap(near potentiometer), a 25v 47uf (farthest from potetiometer), a B222 cap, a c945 transistor (near cap), a953 transistor (near ceramic), a d553 transistor (riveted on a lead), 5 diodes, about 10 resistors. 






When i received the truck, the aftermarket radio's ground lead was wired to the dimmer's output. Radio was not function, replaced with new unit and wired correctly to body ground. If i jump the output on the plug to ground the light on the panel light up, but are too bright for night driving, and being in California, i can get a citation for it.

Please help me diagnose and repair this. You are all awesome people and we can get this working. I will start to identify and measure the resistances. Please guide me to test the rest.

[coppice]

Its called the Pajero in most countries. In the UK its called the Shogun. I think only the US calls it the Montero.

[ricardohd91]

Update: Potentiometer appears to be in working order.

[poot36]

I would start by checking for cracked soldier joints.  If you find none use your multimeter on diode mode to test the diodes and transistors.  It looks like this circuit has a pulse width modulation (PWM) generator that drives the rivated transistor on the ground side of the circuit.  Also make sure that you have 12V at the socket that this module plugges into.  If you can get to the pin of the rivated transistor that is not attached to the ground or light output pin when the module is plugged in probe it with the positive lead of your meter set on dc volts and the negative lead connected to ground you should see the voltage vary with the setting of the brightness control.  If you cannot fix the module you could replace all of the incandescent bulbs that are controled by this circuit with LEDs and then just get an appropriate power resistor (300 to 500 ohms 3 to 5 watt) and use the current variable resistor from the broken dimmer module (assuming that it works) and wire these two components up in series between the ground and light output terminal on the socket for the module.  I am basing my component values on the standard 12V LED replacement bulbs you can get at most auto stores and online.  You may not even need the power resistor depending on how bright the LED bulbs are (I am making an assumption that the variable resistor in the current dimmer is rated to 1 watt or so).

[ElektroQuark]

Quote from: coppice on Today at 06:07:16 PM

Its called the Pajero in most countries. In the UK its called the Shogun. I think only the US calls it the Montero.

In Spain is called Montero too. Pajero has some sexual connotations.

[Dongskie2]

Good day guys!

Any updates on this? I'm currently experiencing the same issue.

Thanks!

[stj]

i would start by replacing the electrolytics - even on a working one.
that thing is going to generate some heat and dry them out.

and use a good high-temp part like panasonic FR series.

[amyk]

It doesn't look like it'd be that difficult to reverse-engineer and fabricate one yourself from entirely new components.

[james_s]

Yes but surely repairing the existing unit would be simpler? Not much to go wrong there, I'd probably draw a schematic to get an idea of how the circuit works. Otherwise just replace those electrolytics and also test the transistors. I suspect it's a simple oscillator with the pot adjusting the duty cycle.