Originally Posted by GARETH T
why didnt you fit a brdge rectifyer on the supply circuit then
Ok here goes....
The power input positive was protected by a series diode to prevent
power reverse polairty which in its own right works fine.
A bridge rectifier could NOT be used as this would raise the ground voltage
level with respect to the vehicle earth about 0.5 volts higher and this
would affect comms signal quality and switching reference levels up.
The problem comes when the lead connecting the tester to the car
diagnostic socket has its own ground in the lead.
So, when the tester is plugged in to the car its own earth is correct.
Then when you connect the GROUND battery lead accidently to positive,
this created a short circuit across the battery - BANG.
The unit was protected with a fusable resistor in the comms lead ground
connection which is designed to blow in such circumstances to protect
from it from fire.
Hope that explains it.
Originally Posted by b19bal
Originally Posted by GARETH T
Originally Posted by SECS
He is talking sh*t.
More likely to have blown a fuse as said above or another earth wire
elsewhere on the car.
As an aside, I dont think most patrol men are "clued up".
I used to work for a company that supplied RAC with diagnostics testers.
They had a RED and BLACK wires for connection to the vehicle battery
and labels on the coloured wires saying positive/negative.,
Nearly had 50% of them returned for damage caused by connecting them
up backwards.
Thick cnuts
why didnt you fit a brdge rectifyer on the supply circuit then
cause he would have lost 80% of his work and also had more waranty claims rather than proof of bad workmanship i guess
mmm
