1985 GT Main Engine Bay Harness Removal

[IDriveFords]

So my paint guy finally came over to give me a quote on painting my 85' resto project and he gave me some bad news (I guess it's only bad if you're lazy). He said I need to pull the entire engine bay harness and all the brake parts if I really wanted it done right (and I do). So yesterday after much swearing I managed to get the dash entirely out without breaking anything that wasn't already broken... Now my question is I see how the wires come out on the drivers side but I can't seem to trace them on the passenger side. Do I need to pull the entire HVAC box system? What wires need to be disconnected on the Passenger side to pull the harness through the engine bay (Without Breaking anything)?

On a side note someone went crazy with undercoat and sprayed all the plugs. Is there anything I can soak this in once its out to clean it up or am i stuck trying to scrape it away with razorblades and screwdrivers?

[Jerry peachuer]

3m adhesive remover and or really good quality bug and tar remover worked for me

I was using heavily soaked rag but it's going to be messy putty knife the bulk of it and use cardboard box to soak up the liquid before tossing out

Good luck

[wraithracing]

To remove the passenger side wiring it is much easier with the HVAC unit out of the way. Not going to say it can't be done with it in place, but I just went thru this on the Saleen Clone I am doing for Erratic50 and that is how I did it.

Good Luck!

[IDriveFords]

TY for the quick responses as always super helpful. I would imagine now that the dash is out the entire HVAC assembly is pretty simple to pull? I can tell you from experience the dash is NOT fun mostly due to the stupid plug connectors Ford used back then (I use two flat head screwdrivers to get them off I dunno maybe there is a trick?). On a brighter note the dash is on my bar undergoing surgery... I even sand blasted and powder coated all the dash brackets. Also while I'm back there is there anything else I should replace that is not on the following list (I really don't want to pull this again if I can help it):

Heater Core
Throttle Cable
Clutch Cable
Speedo Cable
Light Bulbs

I read that there are vacuum lines buried in the HVAC system that run into the engine bay? I have the engine bay pretty much cleared out and don't see any vacuum going from the bay into the cab so I'm not sure if I'm just confused about something.

[tbirdman]

I would definitely replace the heater core if it has never been done. This is the easiest time to replace it, with the dash out of the way and you being able to easily remove the hvac housing.

[boogiestang]

Heater core heater core do it now and be done with it. I second that recommendation. Way easier now.

[IDriveFords]

I should have mentioned the list above are the things I will definitely be replacing I was more-so looking for anything additional (Vacuum lines/Relays etc...)

[tbirdman]

I'm not exactly sure, but I believe that most of the wiring will feed through the driver's side of the firewall into the engine bay. On the passenger side you have the heater core inlet and outlet hoses, as well as the line for the AC evaporator. There may also be a vacuum line for the HVAC coming out of the passenger side. It probably will be a learn as you go sort of thing.

These might not help a whole lot, but here are three pages on the electrical system of the Mustang...







What you can do is see what systems you have already identified as going through the firewall, and that might help you figure out which ones are still left and where they might be routed.

An EVTM would also be a big help.

As far as what to replace while you have the dash out, that really is going to be up to you. The first thing to do is to determine what condition the existing parts are in. One thing I've found out is that it is getting harder to find replacement parts for these cars. A lot of the behind the dash parts are not currently being reproduced, and NOS parts are almost impossible to find. You may find the occasional relay or module here or on Ebay, but as far as vacuum hoses, wiring, HVAC components, you are going to have to probably find the best used parts that you can. If your existing part is in good condition, it's probably best to re-use it.

One thing you can replace and that is being reproduced is the HVAC blend door cable. Over the years they become harder to work, almost to the point that you'll need all your muscle just to move the control on the temperature slider on the HVAC control panel. Again, the cables are reproduced, or you can re-use yours if it's in good condition and lubricate it. I'm sure if you do a search on here you'll find the instructions on how to do that.

As far as the harness clips being difficult to get apart, oh my god they are. They were just as hard when the cars were new, and now that they are 30+ years old, not only are they still hard to get apart, but now they are brittle and usually end up breaking. I broke the clips on my heater blower resistor wiring harness, and was lucky enough to find a repair harness on Ebay that i could source a new harness clip from. I think there is a tool that you can use that might help, but I can't see any tool helping unless you have three sets of hands.

Good luck. If you need any help, just post it and hopefully someone can chime in. If you need help identifying a part, let me know and I'll see what I can do.

And by all means, post pics of your progress. I will be doing the same project to my 85 GT here soon, and it's a lot easier when you have pics to go by.

[IDriveFords]

Thanks for response and I saved those pictures you posted to my project folder as they look like they will be very helpful. There are actually 2 sets of wires that feed through the passenger side but I believe most of them go to what I would call the ECU/PCM but in 85' it was probably called something entirely different. Then there is one single yellow wire that feeds through on that side as well. I have the dash completely out which I managed with breaking little to no connectors so they should all be re-usable. This weekend I plan on doing what Wraith suggested and just pulling the entire HVAC box and leaving all this stuff out when the car goes out for paint. This should make those wires very accessible in order to easily pull the harness.

[dagenham]

I managed to replace my 85 harness under the hood without pulling anything of the dash. It is tricky but you can get the vacuum lines and harness out on the passenger side