ALDL Troubleshooting

[ricmik]

I have a question regarding my Chevrolet G20 ’88.

Here’s the cars data:

 

Chevrolet G20 Van ’88

6.2L Diesel

Automatic transmission

Mileage: somewhere around 65000

A/C and Cruise Control

 

Questions:

 

The ”Service engine soon” light is constantly lit. When I try to short the ALDL to get an error code, I only get the “Diagnostics mode” code (1 pause 2).

Anyway, when I short the ALDL, I can hear the glow plugs relay click (I suppose it should do so) – in addition to a weird fast clicking noise (like a relay is being turned on and off repeatedly). Is this normal?

 

I have a light bulb hanging behind the instrument panel with wire colors: gray/pink-black (pink with black stripe). There’s also a plug with 4 contacts; wires: dark blue/yellow – brown/light blue.

What are these for?

 

Is it an easy way to check that the A/C compressor is working? I can't get any cold air out of the vent.

[GM-Tech]

I'm not going to be much help here. I don't recall what level of functionality the computer had on an 88 diesel G van, or what those wires would go to. I probably didn't even know the latter in 1988.

 

Lots of wires under there and hard for me to guess without even seeing them. Light gray is typically a dash light circuit. Pink w/black is ignition power. Not sure why a bulb would have power from the dash light circuit AND ignition power.

 

As for how to tell if your compressor is working... look at it. Is the clutch engaged when the a/c is on and the engine is running?