Wiring LA3 to control fan in SVO

[xr2300]

Ok, I'm inept when it comes to the EEC wiring.

From what I understand, pin 52 on the LA3 can be wired to a relay to control a fan.  On the Turbocoupe, when coolant reaches 220 F, the EEC grounds pin 52 (HEDF) which turns on the fan.  

The LA3 can be wired in the SVO to control a fan.  What I've read about the wiring looks something like this:

photos.app.goo.gl/xGsguaunsMNqqQW89


My dumb question is,  how does the EEC ground pin 52 when there isn't any relays in the EEC?

And wouldn't putting 12 V through pin 52 before being grounded damage the EEC?

[Stinger]

There aren't relays in the EEC. 87-88 TC's use an IRCM (integrated relay control module) that's mounted on the passenger side inner fender.

Page 2 of this PDF shows how the relays for high and low fan are configured inside the IRCM.

rothfam.com/svo/reference/87Thunderbird.pdf

[xr2300]

Awesome, that makes sense. I didn't realize the TC's had that external relay controller.

[Stinger]

Yep, those, 91-93 Mustangs, and Rangers all used an IRCM.

[xr2300]

Update...Well I got it wired up to a relay. And it works. Funny thing is my mechanical temp gauge reads different from my quarterhorse with binary editor. The mechanical gauge will read around 190, and binary editor will show around 210 when the fan kicks on. Either way, it works.

[Stinger]

Good to hear.

Not overly surprised they read different. It's not all that uncommon, people just typically don't have any way to know they are off.