Rev counter not working

[jasper2347]

Anyone had any dealings with the late 130s rev counters? The wiring diagram insists on a white feed wire on the back of it. No white wire just two linked greens on a spade terminal one earth on a spade terminal and a female bullet terminal with green wire. Car was rebuilt before we got it and the rev counter has never worked. Just thought I would try and get it working while the dash is out. If no joy fixing will just bin it and get a modern one. Cheers.

[HCA]

You should definitely have 'another' wire - white if no one has changed the colour.

rather than get into all sorts of ifs and buts, will you tell us a bit more maybe? Like a good photo of the rear and front (just in case a po has changed the unit). Then have a hunt around for a white wire in the spaghetti behind the dash.

To start you off this is one of the +2 schemes. You might find that the white wire has bypassed the rev counter for what ever reason. But unless someone has hacked at the loom, it will be there.

Screenshot 2021-05-19 at 18.18.31.png (60.66 KiB) Viewed 1064 times

[jasper2347]

Many thanks for your reply. Pics attached. Currently off the car so could be wired direct to coil and feed to test if we know what goes where. Dash out to swap voltage stabiliser. The wired pic is as we found it. Cheers, Rob

[mbell]

WHere does the green bullet connector wire go? Does it go to the coil -ve?

You'd normally have two white wires on those connections, one comes from ignition switch and other to the coil +ve. This allows the tacho to see current pulse to the coil associated with points opening/closing and therefore engine RPM.

It might be your tacho has been converted to RVI from RVC. In which case I would expect the green cable to go to -ve side of the coil.

[HCA]

Rob, you have the Mk2 RVI type rev counter, correct for the car as shown on the photo of the face. i just wanted to check it was correct.

As to the wiring, forget my diagram, it is for a Mk1.

Wiring colours have, and still are, the bain of man’s existence! I confess that I have never seen the signal wire as green. But if anyone was going to fly in the face of normality, then it would have been Lotus.

Green generally is for something completely different, so very wrong to use the colour for this signal function.

So I might not be able to help unless you bring me the car! Let’s try though. On the RVI, there is a clump of three conns - a male spade, a male pole and a female socket. The spade is a swithched 12V. The male pole goes to ign switch pos 2 and the socket goes to coil +.

I can see your green on the male pole - where does this go? I cannot see another green wire though.

You must have a wire - normally white from ign 2 to coil. A tach dits in this circuit. Can you trace what wire you have for this please?

[jasper2347]

Great cars if they work! I was wondering about the trigger wire. Most rev counters trigger from the -coil or contact side. Smiths were always different though. As far as I can make out the green with the bullet type connector goes to, or comes from coil+ have had tester on that circuit. This is of course becomes 12v live with the ignition on. The spade with the two greens seems to be ignition fed also. We seem to be missing a trigger wire? There was no wire at all in the female bullet connector on the rev counter. If between us we can work out which goes to what I will just run new wires from wherever to the rev counter. As you can see the gauge is out right now. I could put it on a different car for that matter for a test. Have an old SAAB and an MGB in the shop for body repairs. Can't fix my own car though!! It is a Lotus. Cheers for your help, Rob

[HCA]

OK, how about this - you say the green wire that is on the male pole comes from the coil. Can you trace the other two green wires? I wonder if they both go to ign pos 2? If so, then one of these should be taken off the spade, and the other to one of the signal poles.

If this is the case, google the wiring for an RVI - I think the male pole is to ign pos 2 and the female socket is to coil.

[jasper2347]

Will have a go. Let you know how we go on.

[jasper2347]

OK then. not a good day regarding the rev counter. Went on the Smiths web site and got the correct wiring setup. Needed a new feed cable as we thought. All cabled up, went to start the engine to test...no start. Fried the Lumention module. Great. Would say there is a fault in the gauge and this has fed something the wrong way round. Could explain why it was not wired in the first place? Luckily we run two Lumenition modules on the race car. Took the gauge off, was tempted to put in to orbit but resisted, plugged the other module in and off we went. Have fit one of our usual new pod mount gauges with a shift light built in and have just used the old thing to fill the hole in the dash. The new one is in place we can see it now as well. At least we managed to cure the other gauges by fitting the new voltage stabiliser, which was why the dash was out in the first place. Many thanks to the guys who posted ideas and info. Live and learn, Especially with Lotus wiring and forty eight year old gauges. If it stops hissing down for more than five minutes, we'll be off for a run before the first meeting next month. Thanks again.

[billwill]

See: viewtopic.php?t=18275&p=147217

and viewtopic.php?t=48725&p=353329