Using LED 18 For Fan Control issues

[widersturbo]

MS1 V2.2 with extra code. 7 year porject that was finally finished a month ago, and I just got the car started and idled running complete standalone on MS1.

I did not assemble this ecu and I'm trying to troubleshoot what's going on, so here's the scoop....

I thought the guy who assembled this unit added what I needed for fan control to run off x12/x2 but he did not. He hooked up the tach output to x12/x2 and said it was on pin 31 of the DB. However after searching around, it looks like x2/x12 runs off of pin 30.

So now I swapped pins 30/31 on the db and 31 should run off of led 18. I have setup led 18 for output 4 - fan control. I'm wired up as followed.

86 - from ecu
85 - ignition
30 - b+
87 - to fans.

I have a 1n4001 diode jumped between terminals 86 and 85 with band side on 85 terminal.

So here's my issue, there is always VOLTAGE on the wire out of the ecu. I don't understand why. There shouldn't be any mods needed for the LED to control fans from what I have read online.

Now I have not had the engine running while the command is taking place, only keyd up.

Is it true that LED18 needs to see rpm in order to correctly operate and the engine should be running before I dig into this any furthur.

Thanks.
MIKE

[Matt Cramer]

Post a picture of how it's modified.

[widersturbo]

Thanks for the reply, I have done all the searching and finally came up this.

The member who built that ECU did indeed give me the incorrect pin out of the DB harness. He had pins 30/31 labeled incorrectly.

I now have the fans coming off of pin 30 of the DB harness and the tach out of 31 which is x14. The pin 30 is used for LED 18 for a fast idle valve/warmup.

I have also verified that the setup on the external board inside the ecu was not the setup for the Fan Control, it was for the tacho output.

So, moving on, I swapped the pins on the connector and got it wired back up to my norma ice cube relay. I am wired as is. 30 B+, 85 From ECU pin 30, 86 IGN, and 87 to fans. Also a 1n4001 diode jumped from 86-85.

With engine running, the LED is lighting up when being told to with the temperature set, FAN/OUTPUT4 indicator is also on steady when its being commanded to, However, still no fans. I have jumped the harness prior a few days back to verify the circuit to the fans and fans themselves are good.

LED18 should be a negative output trigger, however when its being commanded, pins 30, 86 and 85 all have voltage on them.

So unless someone can tell me otherwise, I am back to the drawing board of why theres volatge on there.


I suppose my next step should be to unplug the relay and use a test light to ground and see if the led lights up, or vise versa, test light to voltage, I need to figure out if that LED is outputing Ground or Voltage.

Unless the relay was damaged through this hoop of adventure I am having, or possibly something damaged in the ECU, but then again if the ECU were damaged, I would also assume that the LED would not illuminate.

So, any advice for a newbie? Thanks