1985 v6 to v8 carb swap

mgriffin_2222 · Mar 23, 2026

Doing a v6 efi to v8 carb conversion, would like to keep it clean and factory looking as possible. Anybody remove the TCAS computer and get the A/C to work without it?
TIA

General karthief · Mar 23, 2026

I believe the AC in 85-6 did not interface with the computer.
I could be wrong
But I doubt it
I have the T shirt to prove it.

mgriffin_2222 · Mar 23, 2026

I read elsewhere that it interfaced with the "TSAD" module which was for some funky two speed front drive, but the AC interfaced through this module so if its removed the AC needs to be rewired. Havent dug into the wiring harness diagram to see if its simple or complex.

From Facebook post by Randy Nicholson
For a 1985 factory carbureted car, that computer is the TSAD module which does essentially nothing. The AC runs through it, so if you bypass the module, you would have to wire the AC wiring around it. It was for the Two Speed Accessory Drive which was never actually a working system. EFI car is a different story.

General karthief · Mar 23, 2026

So what is the TSAD module, I search and got efi computers, google is trash, did find a post here but not sure there was a resolution and they were going to run a Holley setup I think, anyway here is that mess...

Electrical Thread '1985 Gt Wiring Questions'

Sep 1, 2017

A little background. I've had a 85GT for 8 or 9 years and it had a 3g alternator upgrade when I got it. I've converted it to Holley Commander 950. I am in the process of replacing the C950 with the HP ECU and want to redo all of my wiring I used to install it originally. I am also wanting to get rid of the TSAD and all the wiring associated with it and simplify the A/C wiring. I am thinking of doing a partial wire tuck. Hide some of the wiring, and add the underhood fuse/distribution box from a SN95. I'm trying to make heads and tails of the existing wiring. My biggest question is...

mgriffin_2222 · Mar 24, 2026

General karthief said:
So what is the TSAD module, I search and got efi computers, google is trash, did find a post here but not sure there was a resolution and they were going to run a Holley setup I think, anyway here is that mess...

Electrical Thread '1985 Gt Wiring Questions'

Sep 1, 2017

A little background. I've had a 85GT for 8 or 9 years and it had a 3g alternator upgrade when I got it. I've converted it to Holley Commander 950. I am in the process of replacing the C950 with the HP ECU and want to redo all of my wiring I used to install it originally. I am also wanting to get rid of the TSAD and all the wiring associated with it and simplify the A/C wiring. I am thinking of doing a partial wire tuck. Hide some of the wiring, and add the underhood fuse/distribution box from a SN95. I'm trying to make heads and tails of the existing wiring. My biggest question is...

droopie85gt

1985 gt 3g upgrade wire tuck wiring

Replies: 3

Forum: Fox 5.0 Mustang Tech

Check out this post on Facebook, Randy Nicholson gives some detail about the TSAD module and its purpose.

T-Top Mustangs | Got this 85 GT and need to get a harness and ECU for it | Facebook

Got this 85 GT and need to get a harness and ECU for it. Last owner put a 88 or 89 harness in it but done it the worst way imaginable. There anyone who even makes a 85 harness or computer or will I...

www.facebook.com

LILCBRA · Mar 24, 2026

Interesting read.... He said something about rewiring around it in his reply.

So I suppose it would make more sense to someone who had a diagram....

LILCBRA · Mar 24, 2026

Dug out my Haynes manual, here are a couple pics that I know include the AC system. I didn't spend a lot of time nor did I scour the pages, so there may be more than this.

The Haynes manual could be beneficial for you, but I think the Prospero diagrams are a lot easier to read. They're larger and color coded. I've not traced any of them to know if there is something wrong with them, but I think they would be a great addition to anyone's tool arsenal.

Ford 1985 Mustang (Fox Body) US Spec 4 pages

Prospero's Wiring Diagrams presents: 11 x 17, Laminated, Full Color Wiring Diagrams for Motorcycles & Vintage Sports Cars! PROSPERO'S WIRING DIAGRAMS offers the Sports Car Enthusiast the finest color wiring diagrams available. Our diagrams are accurate and easy to use - they are based on Factory...

colorwiringdiagrams.com

Or, you can find them on Ebay (which is where a lot of us have found them to begin with).

11 x 17 COLOR Wiring Diagram for Ford 1985 Mustang (Fox Body) US Spec 4 pgs | eBay

Make & Model: Ford Mustang (Fox Body Style). YOU WILL GET A DIAGRAM - NO MATTER WHAT. Prospero's Wiring Diagrams presents 11 x 17 - Bigger than other wiring diagrams. The Quick and Dirty on Our Wiring Diagrams.

www.ebay.com

mgriffin_2222 · Mar 26, 2026

I have the Ford electrical diagrams.. though those Haynes ones look fairly simple, if they're complete and accurate. I'll study the factory diagram and see if I need to get the Haynes or Prospero's, thanks very much for the info! I have located the Unicorn 1985 5.0 carburetor wiring harness in a wrecking yard, waiting for them to pull it from the vehicle, so may not have to modify it at all (fingers crossed!).

mgriffin_2222 · Apr 9, 2026

Figured it out. The v6/efi harness has an A/C pressure switch on the dryer, which interfaces with a full throttle cutout relay and the ECU. Fairly simple to remove most of that and have the switch pass power to the A/C clutch (didnt retain the full throttle cutout relay since we didnt install a switch to detect full throttle).

1985 v6 to v8 carb swap

mgriffin_2222

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General karthief

wonder how much it would cost to ship you a pair

mgriffin_2222

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General karthief

wonder how much it would cost to ship you a pair

Electrical Thread '1985 Gt Wiring Questions'

mgriffin_2222

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Electrical Thread '1985 Gt Wiring Questions'

T-Top Mustangs | Got this 85 GT and need to get a harness and ECU for it | Facebook

LILCBRA

I wish I didn't have all of these balls in the air

LILCBRA

I wish I didn't have all of these balls in the air

Ford 1985 Mustang (Fox Body) US Spec 4 pages

11 x 17 COLOR Wiring Diagram for Ford 1985 Mustang (Fox Body) US Spec 4 pgs | eBay

mgriffin_2222

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mgriffin_2222

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