Thanks for the replies guys, much appreciated.
There is obviously a reverse switch that is wired in and the fact that the other two identical switches are also wired in, grouped with the reverse switch and feeding into the loom tells me they serve a function. My guess was something to do with emissions also.
What I don't understand is how they are not mentioned or detailed in the main text of the workshop manual for the driveline or emissions sections, or even in the wiring diagram......?
As per Nissanman's reply, if one switch was for a 4th gear emissions function, what would that function be, also for the overdrive function?
My car on a trip seems to use more fuel than what others have told me these cars were capable of, if there is an emissions issue which is causing this, I'd like to sort it out.
A recent trip to Adelaide from Mildura in the heat wave before Christmas saw a range of approximately 500 to 540 km for the 60 litre tank.
That's sitting on 110km per hour with the air-con on, 4 people in the car plus luggage.
Fuel used ranged between 11 to 12 litres per 100km or 9.06 to 8.3 km per litre.
US Miles per Gallon worked out between 19.6 and 21.4. It was suggested to me that they are capable of 30?
Condition of the motor always makes a difference of course and my car is an original uncorked motor with almost 160k on the clock. It does puff a bit out the pipe if you give it a rev but there is no visible smoke at idle or low revs, compression is good and it starts instantly, idles well, revs cleanly.
I run Penrite HPR30 Full Zinc in the motor and the gearbox and diff oils are 3 months old with an oil conditioner added.
Basically I'm doing everything I can to make sure the old girl is as happy as possible
The fuel use sounds heavy to me as I used to drive (15 years ago) a 307 chev powered Holden HK Brougham with a Powerglide and 2.78:1 ratio LSD that returned up to 18 mpg on a trip.
Any thoughts guys?