So my tacho is working fine when headlights are on but if lights off it works sometimes but not smoothly and other times is jumping around all over the place and sometimes just not at all. If headlights are on its perfect. It’s Digital I assume and I thought an earth issue but I can’t work it out - any thoughts?
Well I bought it as a gift for myself as doing a lot of hilly driving and like to keep the revs under 3.5k where possible and certainly not over 4k so is a good check to myself
Mmm I have these instructions and pretty sure wired as suggested but will check that red / blue wire - just very odd works perfectly with headlights on - if just side lights then does not work properly either - strange!
I can of course just forget about it and put the headlights on but I have a tendency to forget I put them on in the day and leave them on when parked as only sometimes I get a noise to tell me left on -
Is it well grounded? We had a strange problem like this on a friend bay window. Oil temp raised when he turn on lights, raised a bit more when wipers are working... He used a stock ground location that already was a bit too loaded. Relocated the ground, problem solved
On a more positive note here’s a picture from earlier this week staying in an apple orchard in ottery St Mary - we had the entire orchard to ourselves and plenty of apple tree branches to burn from last seasons pruning
It’s grounded to the metal dash so probably not the best place but wire was short and thought would be ok?
Dash earth is fine. As a first step, I'd try connecting the +ve supply directly to the fusebox. The top of F12 would do (on a Late Bay).
One problem comes from the long wire from the engine bay - when fed with the horrible waveform coming from the average points, it may be causing the rev counter to sometimes count an extra pulse. The supply voltage to the coil goes down when you turn the lights on because of the way the bus is wired. So interference or ringing from the points wire with the lights off may just be large enough to trigger the counting of extra pulses. Did you ground the spare input or just leave the wire hanging around ? You could fit something like a resistor from coil negative to a 12 volt Zener diode in the engine bay, and take a wire from the Zener diode to the counter, that may help. Problems because in a normal classic car, they are designed with one or two metres of wire to the generic rev counter (like you have here with a bus-style face) , you have 5 or 6 metres of wire. If your engine is stock, I would have said 3500 rpm is a bit low for max RPM, more like 4000-4100 rpm is realistic with an unbalanced crank in an AS41 engine case, also a stock engine doesnt really like delivering power below 2000 rpm, power band 2000-4000rpm.
Thanks - this makes sense, I just wired as per snotty’s suggestion but have not tested driving yet as we are parked up so let’s see what happens when I get on the move again. In terms of rpm I have a 2l type 4 and sits really comfy at 60 mph at just over 3000 rpm, hills I really try not to go above 3500 as sounds like it is unhappy but yes agree anything below 2000 is not great either - I typically sit at at around 2500-3500 band. I have used 1 litre of oil in nearly 3000 miles and change oil within every 3500 so about to do an oil change before we head off of France later this month. Engine is original to van and was rebuilt about a year ago and so far so good
In case you didn't know, 5,400 is the red line so it really doesn't hurt to rev it to 4,000 or even 4,500. It should manage 60mph in 3rd and should sound very smooth doing it. I'm not suggesting you drive like that all the time but TBH at 3,500rpm it's just getting going.
Good to know - will take it on a track day We are traveling for another 16 months ( nearly 2 months into our 18 month European sabbatical already) so trying to be gentle as possible to hopefully have less time at side of the road. More than can be said for my 20 yr old Campingaz grill which I had in bits today - was a blocked valve and now back in use
Sounds good to me and what you're doing should see you having a relaxed and comfortable sabbatical. The bus is geared to the rpm and speed you see at 60ish but you've just got to watch the die-back on the revs during changes, especially at lower speeds in towns and villages. We didn't get out of third for about 6 weeks around the Peloponnese one year. It's just not worth lugging the box. The engine may have been rebuilt, but be mindful of the transaxle that will thank you for keeping the revs up
