Electric Rev Counter

[johnwill]

I decided to get my Tacho converted to electric by JDO. (TR4A, Neg earth)

The wiring has 4 wires:-

Black - Already Screwed to back of Tacho case

White - To Constant +ve feed

Red - To Positive Ignition

Green - To Coil negative terminal

Green is straight forward, but has anyone else done this, and where did you connect Red & White to please? White to Fuse box? Red to ignition switch, but which terminal?

Just want to make double sure before I connect.

Thanks

John

 

[RobH]

Have you got that the right way round John?   A conventional colour code usually has red as the constant positive and white as the switched supply.  Is your information from the people who did the conversion? 

Edited April 7, 2022 by RobH

[johnwill]

1 hour ago, RobH said:

Have you got that the right way round John?   A conventional colour code usually has red as the constant positive and white as the switched supply.  Is your information from the people who did the conversion? 

Yes, from JDO

[stillp]

Can't JDO tell you?

Pete

[RobH]

 Your red wire can go to the fuse terminal with the green wires - that is ignition switched and saves having to get at the back of the switch. The white wire can go to the A1 terminal on the dynamo control box. (If you still have a dynamo. If not it depends on how the wiring has been changed).

[johnwill]

Well, they’ve labelled the wires, I just wanted to make sure I connect it properly to my TR.

Don’t think they have TR specific knowledge. 
 

Someone who’s knowledgeable with TR electrics is a better bet I think. 

[johnwill]

1 minute ago, RobH said:

 Your red wire can go to the fuse terminal with the green wires - that is ignition switched and saves having to get at the back of the switch. The white wire can go to the A1 terminal on the dynamo control box. (If you still have a dynamo. If not it depends on how the wiring has been changed).

Alternator Rob… 

[RobH]

To fit an alternator the brown/yellow wire from the ammeter,  the heavy  brown lead from  the alternator, the brown/yellow feed to the horns and the brown/green feed to the ignition switch must have been connected together somehow.  (Often the old control box is left in position and used as a convenient junction point.) That is the point you want for the white wire.  

[johnwill]

Ah. There is separate junction box next to my fuse box that appeared after the alternator conversion. 

 

thanks Rob

[Lebro]

White would normally be switched, unfused ignition feed, but as long as both white & red have +12V then it should work.

Bob

[johnwill]

Thanks

[Lebro]

Still can't think why you would need  a permanant feed, could one of the wires be for illumination ?

Bob

[Steves_TR6]

I have a jdo converted tacho in my 6 so can take a look for you but am away for a few days.

i don’t remember a permanent positive connection and dont see why/like the idea!

steve

[RobH]

1 hour ago, Lebro said:

could one of the wires be for illumination ?

You're right that a permanent live doesn't make much sense - after all the only time you need the tacho to work is when the ignition is on.   I assume illumination is still as standard since the original tacho body is used. 

 

 

 

[Richard71]

Contact Autosparks.........my electronic tacho came supplied with flying leads and they integrated it into the new loom they made for me. There are for wires and one is for illumination, though I don't remember which.

Richard.

[johnwill]

6 hours ago, Lebro said:

Still can't think why you would need  a permanant feed, could one of the wires be for illumination ?

Bob

Something to do with the needle returning to 0 revs I think. Steve at JDO did say, but I’ve forgotten 

[ntc]

50 minutes ago, johnwill said:

Something to do with the needle returning to 0 revs I think. Steve at JDO did say, but I’ve forgotten 

Correct and I should follow the wire labels or on your head be it.

[Lebro]

Tjat suggests that the movement is driven by a stepper motor.

Bob

[johnwill]

I received my tachometer back from JDO this morning. Steve put a video on their site showing it working. 
 

I’ve connected up exactly as described, the tachometer does it’s test (to max then back) but on starting the engine, it doesn’t move. 

JDO not in today, not surprised being Easter. Steve normally works Sat mornings 
 

Is the wire to negative on coil correct? Eg should it be positive? That’s the only thing that can vary isn’t it? (Neg earth car)

not changing anything until I know it’s correct  

puzzled

john

Edited April 16, 2022 by johnwill

[johnwill]

On 4/8/2022 at 9:24 AM, Steves_TR6 said:

I have a jdo converted tacho in my 6 so can take a look for you but am away for a few days.

i don’t remember a permanent positive connection and dont see why/like the idea!

steve

Would be helpful Steve, thanks

[RobH]

1 hour ago, johnwill said:

Is the wire to negative on coil correct? Eg should it be positive? That’s the only thing that can vary isn’t it? (Neg earth car)

not changing anything until I know it’s correct  

The wire needs to go on the terminal which connects from the coil  to the distributor.  

That ought to be the "-" one on a negative-earth car but it is possible the coil could be connected the wrong way round.  

Edited April 16, 2022 by RobH

[johnwill]

3 hours ago, RobH said:

The wire needs to go on the terminal which connects from the coil  to the distributor.  

That ought to be the "-" one on a negative-earth car but it is possible the coil could be connected the wrong way round.  

I found an internal break in one of the wires I was using to test it with….. oops. 
 

replaced that, and all working now, so fitted it to car proper, and all good. 
 

thanks everyone. 

[Steves_TR6]

Good result !

also saves me pulling mine out of the car to check :-)

steve 

[johnwill]

2 hours ago, Steves_TR6 said:

Good result !

also saves me pulling mine out of the car to check :-)

steve 

[johnwill]

The next installment on this....

 I set the Tacho up to test first, and saw it showing the revs as i pushed the pedal down, so fitted it, checked again and it did the same, so thought job was done. Working ok it seemed, but I hadnt checked closely enough....

Took it for a drive a couple of days later, and when running at a constant speed, say at 2300 revs, the needle bumps up to 3000, returns to 2300 then bumps again to the same or higher, including up to 6000 revs. Its every couple of seconds or so, but doesnt seem constant or any pattern (that I could see)

I assumed this may be the wire to the coil (maybe getting a fluctuating signal somehow?), but firstly checked that wire, and all the other wires, including earth, were connected solidly by replacing each in turn with a separate (new and tested) wire, but nothing changed.

Steve at JDO did a video of it working before sending it to me, and it was steady as a rock in that, and has suggested I send it back for him to check in case it got damaged in transit, but before I do that, I thought I would ask on here.

Any Ideas?

Coil is new (Accusparc)

Distributor new (The Doc)

Alternator, not Dynamo

Thanks

John