15 replies to this topic

[L400RAS]

Model: 1293
Year: 1975
Hi,
I bought the rev counter below, and decided to hook it up underneath the bonnet before I cut a large hole in the wooden dash... I ran a new 12V switched live to the terminal marked red +ve, the black -ve i earthed to the engine block, and the trigger I connected to the - negative on the coil. The needle does not move regardless of where the switch is (can be for 4,6,8 cylinder). I am getting approx 12V out along the earth cable. Wondering if anyone can suggest where I am going wrong?

The seller stated it was tested on a car, however since then it has been in the hands of Mr Postie... (sorry for implying anything if there are postmen/ women about)

The car has electronic replacement for the points - hence buying an RVC counter.

many thanks
Ryan

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Edited by L400RAS, 18 October 2010 - 03:59 PM.

[stevede]

There will be others that no more about this than I, but I think your last sentence may be the issue.

It looks an older style RVC maybe not designed for electronic.

Can you try it on another car with points? May answer you question.

Good luck

Steve

edit: spelling

Edited by stevede, 18 October 2010 - 04:26 PM.

[L400RAS]

It looks an older style RVC maybe not designed for electronic.

Hi steve,
RVC is designed for electronic (its RVI that isn't), so pretty sure this is not the cause, but thanks though

[Gulfclubby]

It looks an older style RVC maybe not designed for electronic.

Hi steve,
RVC is designed for electronic (its RVI that isn't), so pretty sure this is not the cause, but thanks though

Sounds like it's simply broken. Take it apart and have a look at the mechanism and electrics inside. I had to go through 2 defective units before I finally got a working, new smith's unit. Always suspected my wiring but it was just bad luck, the new one is working perfectly. I'm assuming this is a non-stepper Smiths tacho, right? They seem to be pretty fragile.

[L400RAS]

Sounds like it's simply broken. Take it apart and have a look at the mechanism and electrics inside. I had to go through 2 defective units before I finally got a working, new smith's unit. Always suspected my wiring but it was just bad luck, the new one is working perfectly. I'm assuming this is a non-stepper Smiths tacho, right? They seem to be pretty fragile.

Thanks for the input Gulf. The seller sounds pretty honest, and has offered a refund if I cannot get it working. To me it seems bust.
Not sure what you mean about non-stepper, havent heard this term before. If i take it apart, I won't know what i'm looking at, so won't bother.

Thanks
Ryan

[Gulfclubby]

Sounds like it's simply broken. Take it apart and have a look at the mechanism and electrics inside. I had to go through 2 defective units before I finally got a working, new smith's unit. Always suspected my wiring but it was just bad luck, the new one is working perfectly. I'm assuming this is a non-stepper Smiths tacho, right? They seem to be pretty fragile.

Thanks for the input Gulf. The seller sounds pretty honest, and has offered a refund if I cannot get it working. To me it seems bust.
Not sure what you mean about non-stepper, havent heard this term before. If i take it apart, I won't know what i'm looking at, so won't bother.

Thanks
Ryan

A stepper tacho is one where the needle moves in small steps instead of spinning freely, the electronics behind it are a lot more sophisticated than in a "normal" tacho. That way you get sort of an "average" value and the needle doesn't spike and jump at all.

[dklawson]

I cannot read the text in the two pictures. What does the text say at the bottom of the gauge face? Are the two power terminals on the back marked +VE and -VE?

My gut feeling is that you may be misinterpreting the power connections. I don't think BOTH should be marked as " VE ". The way they are marked implies that one is the power connection IF the car is negative earth. The other would therefore be the connection if the car is positive earth. Of course, the gauge case would be "earth" so the lamp would power up.

I'll do some digging later but you may want to contact the seller to see if my suspicions are correct.

[GreenMini17]

Have you tried wiring the tacho in by just onto the negative or positive (I cant remember which) side of the coil? Then just earthing it through the body?

There will also be a negative and positive for the back lighting. Non of the smiths classic range is stepper motor driven I don't think, they are not the gauges they used to be.

[L400RAS]

What does the text say at the bottom of the gauge face? Are the two power terminals on the back marked +VE and -VE?

Face says RVC1003/00F. The terminals are labelled:

LEFT: +VE (RED)
MIDDLE: -VE (BLACK)
RIGHT: Trigger (Blue)

How i wired it:
12v feed to the +VE, earth to -VE, and negative side of coil to trigger.

Doug, do you think i should only supply the unit with 12V on the +VE? - if i disconnect the earth it still does not work. I have measured voltage on the -VE pin without it connected to earth, and it shows approx 12V (fluctuating).

[Dan]

- if i disconnect the earth it still does not work

You would have to earth the casing and power the +ve terminal if Doug is right, as he may well be. The -ve terminal would not be used.

[L400RAS]

- if i disconnect the earth it still does not work

You would have to earth the casing and power the +ve terminal if Doug is right, as he may well be. The -ve terminal would not be used.

Thanks Dan, I will give this a try tomorrow:
12V to the terminal marked +VE
ring terminal to the body
trigger to the coil.

Cant hurt. Yes, seen Doug post many times regarding electrical issues - very knowledgeable.

thanks guys,
Ryan

Edited by L400RAS, 18 October 2010 - 06:45 PM.

[dklawson]

Ryan, I tried finding more info on line regarding the 1003/00F tach. I found them mentioned several places but none had wiring information. Several other aftermarket 1000 series tachs are listed as suitable for positive or negative earth so my gut feeling is that your tach is also.

I'll continue looking and post anything I find.

[L400RAS]

doug, so if i earth the case, which terminal should i put 12 volts to +ve or -ve? my car is negative earth by the way.

[L400RAS]

I tried earthing the case, and 12V power source to +VE terminal, negative coil to trigger terminal, with no success. I will borrow another known good rev counter tonight to test my wiring, but I think I will be returning this one. Shame, looks great.
Ryan.

[L400RAS]

Hi all,
update: it's now working! Cause of the problem - a poorly crimped spade on my earth lead (sorry for being stupid everybody...)

If anyone in future is reading this with the same tach as myself, I connected it up in the following

For a NEGATIVE earth car:
+VE terminal =12V
-VE terminal = earth
Trigger terminal = negative side of coil.

For positive earth I ASSUME the power connections are reversed.

I did have to earth the case as well - the bulb holder did have an earth "fly lead" however this had broken off, so i just thought a ring connector to the stud would suffice for bulb earth only.

thanks again for the input,
Ryan.