|The MGA With An Attitude
WIRING HARNESS REPLACEMENT
"Do you have any info or wiring harness replacement?"
Okay, when I get bored late at night write longer memos. The MGA harness installation is pretty straight forward.
In general there is a substantial trunk of the harness running across behind the dash, where it is mostly supported by being connected to the instruments. The only connections there not on the back of the dash are for the headlight dipper kick switch and I think one ground loop bolting to the firewall. Wire terminals here are ring lugs on the back of the instruments (and one to ground on the firewall), a couple of bullet connectors for the heater blower switch, and bare wire ends for screw posts on the switches. Four instrument lamps are part of the harness.
There is a single large passage through the firewall (large rubber grommet), then another substantial trunk running left and right along the front of the firewall, mostly just laying on the heater shelf. Here the terminals are bare wire ends for the voltage regulator and fuse box, bullet connectors for the heater motor, forked lugs for the turn signal relay box (MGA 1500 only), and ring lugs for the flasher unit and wiper motor. Also one large ring lug where it picks up power at the large battery cable on the starter switch, and a bundle of bullet connectors near the starter switch (to connect the front to rear harness).
From there the main harness runs forward over the right side inner fender with one or two p-clips to tie it to the wall. Then it runs past (under) the body diaphragm beside the radiator down to a location just inside the right inner fender corner ahead of the radiator, then across just inside of the grille to the left inner fender corner, just lying on the air panel ahead of the radiator. From these two corners the harness runs down through rubber grommets to the headlamps, parking lights and turn signals. Also from the right front corner a couple of wires run across (loop around) the large tube of the front frame extension to connect the horn(s), and one more to connect the (optional) fog lamp(s). Wire terminals here are all bullet connectors with a bundle of them ahead of each front tire near the corner lights, and one or two for the fog lamps. The bullet connectors for the horns terminate inside of the domed horn covers, with a small rubber grommet for the passage through the cover. There are grounding wires with large ring lugs that attach to a body to frame bolt at each front corner.
Very near the manual starter switch (on the frame to the right of the engine) there is a junction with the harness running to the rear of the car. Here you find a bundle of bullet connectors to connect the two parts of the harness. As it drops from this point a pair of wires (bare ends) split out for the hydraulic brake light switch at the 5-way hydraulic block on top of the lower frame. Then it runs back under the floor along the inside surface of the right side frame rail, held in place by a few bend-up clips welded to the frame. Near the front of the RR wheel a wire breaks out for the fuel pump (bullet connector, and the fuel pump has a grounding wire to the frame). Then beside the fuel tank one more wire for the fuel level sender unit (ring lug), and one wire for grounding on the frame at that point, where the harness is also mounted to the frame with a p-clip near the fuel sender unit. The front to rear harness terminates just behind the RR wheel where it connects to the rear cross harness with another bundle of bullet connectors.
The rear cross harness passes along the large round tube across the rear of the frame, where it feeds the tail lamps, turn signals, and license plate lamp, and is held in place by a pair of thin straps around the frame tube. There are rubber grommets where it passes through the underside of the rear fenders to the tail lamp housings, and another grommet where it passes through the rear valance at the center of the rear bumper on its way to the license plate lamp. As I recall all of these wire terminals are bullet connectors that plug directly into connectors inside of the lamp housings.
When removing the whole harness, start at the four corners of the car, disconnect all of the lamp wires and ground lugs and withdraw the harness in the general direction of the starter switch. With the front to rear harness disconnect the fuel sender unit, the fuel pump, and the brake light switch along the way, dismounting p-clips and unbending retainer tabs as you go. Near the starter switch you can disconnect all of the bullet connectors, or you can leave them connected to remove the entire harness in one piece.
For the main harness disconnect all of the wire ends behind the dash (including the kick dipper switch and a ground wire). Also disconnect all of the wire ends in front of the bulkhead (where the ground wire terminates at the voltage regulator). Withdraw the main harness through the large hole in the bulkhead.
Now assuming you can remember all that, reassembly with the new harness is simply the reverse of disassembly. And you may find that putting the new one in doesn't take much longer than ripping the old one out. Just pay close attention to the color codes on the wires, because there are absolutely no polarized harness connectors in this car, and all wires are single point connections. Where wires branch for grounding connections or split for parking light and headlight wires there are multi-way female bullet connectors to accept the single loose wire ends. In spite of the illustration in the catalog, there are no 3-way female connectors, except for gtound wires at the rear of the 1600 cars.