View Full Version : wiring interchange questions

08-02-2009, 09:22 PM
Ok, I am going to be installing the dash and interior wiring harness from my 90 into my 89 this week. I've been trying to search but haven't been able to find the info I was looking for.
The 90xr7 dash/harness I'm using is from an automatic car and my 89xr7 is a manual. My main concern is about the starter interupt circuits.....I have heard that they are different between the years, so what would I need to do???
Also can I splice into where the automatic trans wiring is under the dash, into my 5 speed trans harness??
Any other information you guys have about this would be greatly appreciated!

XR7 Dave
08-02-2009, 09:42 PM
Yes the harnesses are different. If you are going to have the dashes both out, you might want to go ahead and swap the harness. Otherwise you have to splice into the main harness to connect the proper switches. I've done it before but it wasn't fun and I don't have a diagram to follow, sorry.

The transmission harness is the same, the problem centers around the clutch switch (which isn't there on the auto harness).

08-02-2009, 09:50 PM
The 89 dash wiring is melted in a few spots between the fuse box/main connector. So, that 1 foot section of harness that I spoke of, I am probly going to de-pin the fuse box and re-pin in the section from the 90?
Also, if I use the existing (good section) of the 89 dash wiring into the 90 dash, I should be using all the modules, relays, etc?
Thanks again

I know this is going to be a pain in the a** I hate wiring:mad:

XR7 Dave
08-02-2009, 11:21 PM
The 89-90 wiring is the same, so you should be able to swap any sections you need. The pigtail for the clutch extends from the middle of the main harness, right behind the instrument cluster, that is the only part you really need if my memory serves correctly.

The auto has the relay for the "must press brake pedal to start" which can function with the 5spd but I recommend either not saving that part of the harness or if you end up with it, just bypass the relay to avoid having to change any wiring. That relay is in the cavity above the fuse box.

08-03-2009, 01:10 PM
So, if i installed the dash and harness the way it sits, I would just need to hold the brake pedal down to start the vehicle correct?
Im not to worried about a clutch switch since I always put my foot on the brake and clutch pedals to start the car>
Any other input would be greatly appreciated!!!:):)
Thanks as always

08-03-2009, 03:13 PM
if you are on cruise and shove the clutch in the engine will rev to the limiter since the clutch also cuts the cruise off...............Dan

08-03-2009, 03:24 PM
Excellent info so far guys!!!
I barely ever use cruise control, always in 5th gear if I do, I'll just remember to turn it off before I hit the clutch:rolleyes:
So installing the automatic dash, this is all Im really looking at for issues?