9 replies to this topic

[Snight123]

Hi,

I'm having a problem with the voltage regulator on the centre speedo clock.

Bit of background, car started life as a 1990 mini City 1000 with twin clock in front of driver, new front loom installed and conversion to centre speedo setup, 998 engine replaced with 1275, loom made with no ballast wire as going to convert to electronic ignition in the future.

I've connected up the centre speedo wiring loom and all looks good, turn ignition on and voltage regulator starts to smoke and get extremely hot, double white wire is connected on terminal b, then two light green connected on I terminals. 12v on white wires, 10v on greens, after about a minute voltage disappears from light greens but 12v still on whites. I have tried an original smiths voltage stabiliser and a modern day LM7810 voltage regulator, both fail after a minute or two.

Any ideas of where to start looking would be great please.

[KernowCooper]

Ok sounds like the regulator can't handle the current, pull the greens off to the instraments and connect the white feed onto the B terninal and earth the stabliser and put a test lamp on the I terminal if this lights up and stay constant, then it proves the regulator can supply output voltage, then check that the greens to instraments are not shorted out somewhere.

 

The Smiths regulators were only rated at 1.5amps

[Snight123]

Thanks I'll wire up another regulator and test it out, I'm only running the fuel gauge and temp sensor. I'll check the greens for shorts though it's a new loom.

Should the central speedo be earthed separately back to the shell in addition to the earths running in the main loom?

[KernowCooper]

The centre speedo dhould have a Black Earth wite onto the speedo assembly, which is all it needs and the full diagram is below if that helps, check those gauges are not faulty and shorting to earth in their cases as that would turn the Smiths Regulator and Aftermarket ones inside out lol

 

Test the gauges by providing 12v to the Green inputs with a tester if you have one (ealey PP1/PP2/PP3 Power Probe) and see if they have issues

 

 

Doug AKA DKLawson did a excellent write up of Voltage Stablisers which I have attached below

Attached Files

•  voltage stabliser wiring.png   140.14K   12 downloads
•  Voltage Stabilizers By DKLawson.pdf   376K   26 downloads

Edited by KernowCooper, 15 September 2015 - 06:54 PM.

[Snight123]

Thank you, great information, tested the fuel gauge for earthing out and your spot on, it's earthing out onto the speedo so off to try and insulate the fuel gauge from the speedo face

[KernowCooper]

So the green feed from the Voltage Stabliser into the Fuel gauge is making the body of the gauge live and a dead short, so the gauge is faulty internally, maybe better to pich up a new unit, here on Minispares http://www.minispare...fuel gauge.aspx

Edited by KernowCooper, 15 September 2015 - 08:19 PM.

[dklawson]

Agreed.  Replace the defective gauge.  It will be difficult to insulate it from the speedometer case and may cause problems in the future even if you do manage to isolate it now.

[Snight123]

Thanks, found another speedo in my parts and swapped out the fuel gauge, that one tested fine with no shorts to earth now

[KernowCooper]

Amazing the different shorts that you come across working on cars just when you think you've seen it all along comes something new, glad your sorted

[Snight123]

Thanks for the great information, I thought I'd wired it up wrong, didn't think it would be the gauge shorting