Convenience Wiring Harness

[Russ McElwee]

Good morning and Happy New Year. Once again, I come to the brain trust for guidance this time regarding the Convenience Group harness. I have a 71 Mach 1 with gauges, tach, power windows and heated backlight. Car came to me in pieces – and I mean pieces. Without too much detail – stripped to bare bones, blasted, replaced rot, painted, rebuilt engine, front-end, rear-end, etc. Everything has been touched and renewed. Midlife reworked both the dash and engine compartment harnesses. Reworked Tach and Amp meter by Rocket Man (modern Tach and Volt Meter). Everything works (all exterior lights, horn, wipers and heated back light circuit as far as I can tell without window being installed), but not the power windows. I have a new Circuit breaker on the junction block and a new Window Safety Relay. Fuses are good. Have purchased every wiring diagram including both the 71 and 73 Forel Publishing, Classic Car Wiring, and the 71 and 73 Mustang Wiring Diagrams. I have no power to the #175 – Black with Yellow Dot wire. I have power from the Accessory Pin on the fuse box to the Window Safety Relay (#298 – Purple with Orange hash) and I have continuity from the Safety Relay to the window switch bank (#400 – Light Blue with Black dot). Every diagram shows a dotted, hash or semi-circle connection between the Starter Relay and the junction block. Where do I get power to the #175? Jumper from Starter solenoid? But that means constant power to that circuit. Has to be a jumper somewhere from the Acc/Run switch to that circuit. Just cannot find it on any diagram. Driving me crazy for two weeks. Getting nothing else done.

 

[Hemikiller]

The junction block should have the two Black w/Orange stripe wires, in addition to the circuit breaker. One is from the alternator harness, the other from the engine compartment harness. The heavy Yellow should be on the starter solenoid lug.

 

[Doug's 73 Mach1]

The circuit breaker should be connected to the battery side of the starter solenoid. The black yellow dot wire to the circuit breaker and have power all the time. The circuit breaker/ black yellow dot wire feeds power windows and rear defrost (these are only activated with their relays energized) . On a convertible it the feeds the power top. It also feeds the convenience group auto seat back release system. The later two systems don't require the ignition on to operate.

 

[Hemikiller]

I have a 71 Mach 1 with gauges, tach, power windows and heated backlight. ..... I have no power to the #175 – Black with Yellow Dot wire. I have power from the Accessory Pin on the fuse box to the Window Safety Relay (#298 – Purple with Orange hash) and I have continuity from the Safety Relay to the window switch bank (#400 – Light Blue with Black dot). Every diagram shows a dotted, hash or semi-circle connection between the Starter Relay and the junction block. Where do I get power to the #175? Jumper from Starter solenoid? But that means constant power to that circuit. Has to be a jumper somewhere from the Acc/Run switch to that circuit. Just cannot find it on any diagram. Driving me crazy for two weeks. Getting nothing else done.

Yes, the Accessory Power Feed #175 is powered full time. The Window Safety Relay is what controls the power to the windows themselves. When you turn the ignition to "on", you should hear the WSR engage with a "click", as it receives power from the Accessory Post and the #298 wire, completing the circuit between #175 and #400.

My recently purchased 71 XR7 has power windows, and they were inop when I bought it. The PO had replaced a bunch of parts, hotwired things and made them "work". Turns out the only thing that was wrong with the entire setup was a bad connection between the #175 wire's fork terminal and the circuit breaker. Took me five minutes to find the problem and three swipes with a piece of sandpaper to fix it.

I would start with the #175 wire assembly itself. Try jumpering the circuit breaker to take it out of the equation, then work your way through the wire. Could simply be corrosion under the factory terminals.

The circuit breaker should be connected to the battery side of the starter solenoid.

On gauge equipped cars, the CB was moved to the terminal block.

 

[Russ McElwee]

Thank you gentlemen. I currently have the Circuit Breaker attached to one end of the Engine Compartment harness (#175 circuit - Black wire with Orange Dots) through the copper terminal off-set extension to the terminal block (have the gauge package). The other heavy black wire on the terminal block is from the alternator harness. There are no other wires attached to the terminal block. The main power circuit (#37 - Heavy yellow wire) is attached to the Starter solenoid. Per HemiKiller picture above it appears there are at least two other wires on your terminal block - and in your diagram cutout on your second post there is one additional wire attached to the terminal block. First time I have ever seen a picture, wiring diagram or had a discussion indicating a third wire on the terminal block. In your attached picture assume either the #6 wire or the #8 wire is the alternator wire. Is the other one a jumper from battery side of the starter solenoid? Doug's 73 Mach 1 - You exactly described my understanding with the exception of the additional terminal block.
I have cleaned everything before assembly - the Power Window Safety Relay is brand new (and they truly do like that one - got to give them your right arm for them to send it to you). I do hear the Safety relay click so the connection is there between #175 and #400. I have taken the #175 circuit breaker (which is also new) out of the loop and connected #175 directly to the battery - the system works fine. Also works fine with the circuit breaker in the loop attached direct to battery. So am I being hardheaded and making this more difficult than it is (which often happens) and simply need to add a jumper between the terminal block and the battery side of the starter solenoid? I was thinking power for #175 circuit should be from the Acc/Run side of the ignition switch so as not to be live all the time.

 

[Hemikiller]

There are two Black w/Orange stripe wires (38, 38A) in a gauge equipped car, one from the alternator harness (#38A), and one from the main engine bay harness(#38). Both *must* be on the terminal block. If wired otherwise, the ammeter will not function properly.

The #37C->#37B->#38 wire circuit forms a path to the terminal block, with #37A providing power from the splice to the fuse block. The ammeter monitors this circuit with 654 & 655.

If you have power to the WSR with the breaker removed from the circuit, then it's most likely bad. Check it for continuity.