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Rewiring of the Herald will include the upgrade to a regulated 60 Amp Alternator and conversion of the complete system to NEGATIVE Ground.
A schematic of the electrical system upgrade is illustrated below with Blue lines indicating the upgrades. (Click on image for full size image)
This NEGATIVE Ground conversion is NOT for novices nor anyone uncomfortable doing internal rewiring of some of the instrumentation. The most critical and difficult modification is that of the Fuel Level Gauge. It is relatively straight forward but involves disassembly of the gauge and rewiring it's internal circuitry. A photo tutorial of the Herald Fuel Gauge modification is linked below.
Besides the Alternator and conversion to negative ground, wiring upgrades on the Herald will include a circuit breaker panel, a lighting upgrade including, relay isolated halogen headlamps, driving lights and fog lights, additional side flashers, an in-dash voltmeter, in-dash oil pressure gauge, Hazard Flasher, 12 volt accessory power outlet, cigar lighter, and updated radio/CD system.
Here is the Fuel Gauge Modification Photo Tutorial and once I get the fuel tank sending unit out of the tank I will document the gauge calibration procedure as well.
(03-11-07) I modified the fuel gauge, connected it up to the fuel level sending unit and all works well with the negative earth system. Since then, I picked up some AutoMeter Arctic White gauges to add to the dash instrumentation. As I was mounting the gauges in the dash I noticed that the original Water Temp and Fuel Gauge looked a bit shoddy in comparison. So, I got a new AutoMeter Arctic White water temp gauge and after some sorting out of the electrics I selected the AutoMeter 1318 Arctic White Fuel Gauge. This fuel gauge registers full at 30 ohms and empty at zero ohms. The Herald fuel level sending unit ranges from 70 ohms full to zero ohms empty. I attached a 50 ohm resistor in parallel with the fuel sending unit (T terminal to Ground) and the gauge reads correctly. The dash will have a very nice look now with the Artic White gauges clustered around the white face speedometer.
Here is a look at the new dash layout with full instrumentation; Oil Pressure, Water Temp, Fuel Level and Volts. Not perfectly symmetric but the Oil Pressure gauge cutout was already there and there wasn't quite enough room to get the Voltmeter spaced exactly the same.
(03-14-07) I visited a local auto salvage yard (A Breaker to you folks on GMT) and dug around through his switch bin until I found a decent Hazard Switch. It simplified my wiring considerably and will make for a very neat installation. The updated wiring diagram, including the Hazard Switch internal routings, is shown here.
(03-29-07) After several days of sorting out the Intermittent Wiper Switch that I picked up at the salvage yard, I finally got it working with the Herald wiper motor. The delay module that came with the switch from a 1986 Ford F-150 truck provided
switched 12 volts to the wiper motor. The Herald wiper motor wants to see a switched earth. Fortunately, when I bought the relays for the upgraded lighting I picked up a couple of extras. I ended up wiring the delay module to a pair of relays that
in turn controlled the wiper motor and provides feedback to the delay module to let it know the wiper motor started. I will probably replace the pair of relays with a single double pole relay but at least I got things playing together nicely with no smoke. I wired up the two speed blower fan switch too. I had to epoxy a trimmed down
10-24 nut into the Herald's Panel Light Swith knob and scraped off the 'EL' on the switch so now it says 'PAN' that really looks like "FAN" in poor light. I am replacing the Panel Light Switch with a Panel Light Dimmer that will get mounted on the other
side of the instrument cluster by the Fog and Driving light switchs. The new two speed "PAN" Switch will go where the Wiper Switch was and the new Intermittent Wiper Switch will go where the Panel Light Switch was.
Here is a look at my bench setup of the wiper delay switch, delay module and relays. You can see the new two speed fan switch by the pliers.
(04-02-07) I didn't get any work done on the Herald this weekend as I was 'redirected' to do some much neglected work around the house. I did manage to update the wiring diagram to include the latest upgrades.
(04-09-07) I'm still sorting out the wirng and when I tore down the steering column I found that the headlamp switch was broken. I don't really care to have the headlamp switch on the column so I checked the parts car and found it had a Hi/Lo dip switch on the column. I will put the Hi/Lo dip switch in, remove the U.S. model floor mount dip switch and I picked up a replacement dash mount, headlamp switch at the Salvage Yard. The switch I got has the instrument light dimmer built-in which will hookup to the instrument lights. I also found that I have an ignition switch with an Accessory position on it so wiring will be modified to accommodate that as well. I wired everything up on the bench tonight and I've now got; Intermittent, Low speed and High speed wipers, electric washer pump, two speed heater fan, Hazard flasher, Left and Right turn indicator lamps, Fog and Driving lamp switches and pilot lamps and adjustable instrument lamp brightness. About all I'm missing is a "Headlamp On" alarm. I updated the wiring diagram, again, to reflect the latest changes. One of these days, when I start mating the dash wiring to the main wiring harness, I'll update the wire colors. I am going to try to salvage as much of the original wire harness as I can but I will still need to remove some wires, add others and mate it to the Circuit Breaker Panel and the Relay Block.
(10-30-07) I've been neglecting the electrical stuff for a few months while I did chassis reassembly, body work and started reassembly of the drivetrain and bulkhead mechanicals. Tonight I was quite surprised at how easy it was to mount and align the Delco 12SI Alternator. The mounting lug face to pulley V-groove center was almost exactly the same on the alternator as it is on the old dynamo. All that was required was a longer spacer between the two lower mounting points on the engine and an extension for the upper adjusting bar. I found that the various belts I have on hand are either just too short or just too long. A trip to the auto parts store will solve that though.
