LS3 convertion with rev counter problems

[UFO MATT]

Hi all. Has anyone on here had a topcats or personal LS3 convertion and had problems with the rev counter? I am having a problem where the rev counter stops working after anywhere between 10 and 30 mins driving depending on how hot it is? I have been told conflicting answers to what the fault could be. I believe its a heat related problem as it can start working again if you get a good run without stopping or traffic. If it's a faulty crank sensor would I not be getting other running problems?
Many thanks for any help

[UFO MATT]

Both the digital and analog rev readings drop out at the same time and return at the same time. There is no other problems or loss of display on the dash when it happens only the rev counter. I am not hugely electricly minded so if I get a professional to look I need to give him some idea where to start.

[UFO MATT]

I have removed the pod and checked the connections. I have also removed the dash ecu and by elimination it's the green plug that supplies sensor readings. Do you have any idea witch one is the tac wire? The Sagaris manual does not tell you as far as I can see it only has the main ecu diagrams. If I can find out what wire it is I can test it to see what side the fault is.

[UFO MATT]

samnorthy said:

The wire should be white and black it goes to pin No 15 on the green dash plug.

Cheers will have a look.

[UFO MATT]

I have traced the tac wire on the dash ecu and there is still a signal being sent after the display has dropped out. I have also removed and turned round the ribbons from the dash ecu to the dash pod and it still does it. I have removed the dash to look for dry solder joints but can't really see any. Any more ideas anyone, starting to loose hope :-(

[UFO MATT]

I have run the engine until hot without the dash in the car so it's cool,connected the dash back up with a fan blowing on it to keep it cool and there is no tac reading!!! I am beginning to think it's not a dash problem as that test eliminates that.i also kept the dash ecu cold to see if that was the problem. I guess now it can only be a tac pick up sensor problem or a problem with the Gm 429 ecu loom interface with the tvr remaining loom.?

[UFO MATT]

Initial needle sweep is normal when the ignition is turned on. That is always fine. That is another reason I'm sure it's not a binnacle or dash ecu problem.

[UFO MATT]

Don1 said:

If it worked before, and it's like this after the conversion, then isn't it the job of the garage to fix it?

Tricky when they are on the other side of the world :-)

[UFO MATT]

Ok I have had the Gm ecu read with an OBD reader and there are no sensor fault codes. I did a meter reading and there is 5volts coming from the Gm ecu supplying the tach feed. Does anyone know if this needs to be more like 12volts? Did the original speed six tach feed have a higher voltage being an older system?