My fan switch has two LED's, which light up when the computer turns on the fans too. Well I was driving today and I notice both LED's turned on (temp was at about 190) and then my SES Light stayed on.

Also shortly before this, my speedometer stopped working. The fan thing happened twice and stops after I turn the car off then back on.

 

I had a similar thing happen on mine when I had my fan switch hooked up, not the speedometer problem, but the SES would come on occasionally like you I had two leds and sometimes when both of them would come on it would trip the light I narrowed it down to it only happening when I was using the A/C for an extended period of time. I don't know why this would make the light come on but it did.

 

My A/C was off.

One of the lights does come on when the A/C is on though.

 

The SES caused the fans to come on (often there is a slight lag time between the two). That is normal. A 1993 can easily flash trouble codes, so there is no need to wonder what it is all about.

The primary fan LED should light when you run your a/c. The fan is supposed to run with the a/c. Again, normal.

 

Trouble Code 24 flashed up:

"Vehicle Speed Sensor (VSS) circuit"

Is there anything I should check before changing the vehicle speed sensor?

Also, I tried looking for the sensor using both the A/C Delco number and GM Number and couldn't find either of them.