Hi,

I am interested in reverse engineering the Climate Control III Junction Box, part number 126589032100. Is there anyone who would be willing to take one apart and take pictures of the PCB?

It's true you can test the pins, but I wanted to have a junction box that was simple to use like an OEM. See attached photo. Thank you very much!

Attached Thumbnails

     

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Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )

Probably better to try and replicate the function than to actually try and copy the PCB and components. Now that we have MOSFETs, and dirt cheap microcontrollers, things are much easier.

It seems that this is just a way to illuminate indicator lights to diagnose the HVAC system?

The original diagram I sent has notes in it that my father helped me with. A transistor may act as a switch or an amplifier, and logic may take place depending on voltage inputs that may or may not exist. Don't know what the diode with the symbol is, but my best guess is that it's the LED, although the symbol is closer to a silicon controlled rectifier (SCR)? I'm not sure.

Anyway, I completely agree with interpreting the function of each test.

Let's start with test #1:

Attached is the test. Pins 1 and 6 should have voltages greater than 11 volts. Pin 6 is assumed to be ground. Further, I assume that no circuitry is used from the junction box. Position 1 of the knob connects pin 1 directly to the cable to test voltage.

Attached Thumbnails

 

__________________
Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )

I'm reading it differently the voltage should be less than 11 volts that's what the diode is for just don't know how much drop across the diode

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

The test is for the supply voltage, so it should be >11V (greater than 11 volts).

__________________
Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )

I think it's a Zenner diode, as the polarity is opposite from that of an LED.

https://en.wikipedia.org/wiki/Zener_diode

I'm guessing it's used as a step down from 12v to maybe 5v for TTL.

https://en.wikipedia.org/wiki/Zener_diode#/media/File:Zener_diode_voltage_regulator.svg

I realized this box may be much simpler than I initially thought. The circuit we are looking at may not be inside the tester itself. Electronic switching unit for temperature control is component #9, which is already in the car. For most tests, the battery is also disconnected.

So the question is:
1. Is this box simply a junction that selects the pins that we should test directly without #9 circuit involved?
2. Does this box have a duplicate #9 compenent and we have to include the #9 for the circuit tests? If so, maybe we make a dongle or breakout that let's us test the invidual pins, with the #9 component from the car in the circuit?

__________________
Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )