Short Circuit in A/C control panel 306 Phase 2 and 3

[dlittlelion]

The most common causes for blowing the air conditioning fuse is a blower motor overload or a short in the air-conditioning control panel. It is best to eliminate the blower as the fault simply by unplugging it. If the fuse still blows it is best to disconnect the control panel.

This is the easiest way to determine whether the fault is in the A/C circuit board or not.

1. Isolate the short circuit by disconnecting the A/C panel then replace the fuse (new)
2. If this confirms the fault then proceed with removing the control panel and dismantle.
3. Remove the large zener diode adjacent to the blue connector labeled D280 on the the A/C circuit board
4. Plug the A/C harness back into the circuit board.
5. Does the fuse still blow? If not, then you are almost there.
6. Check all functions to ensure that all is ok.

At this point you have a choice to either reassemble the panel without the Zener Diode which means no over current protection (very popular choice) or to replace it (1N5351B).

A common mistake made by the average auto electrician is to install a high wattage rectifier diode.

It is not unusual for the earth and main power supply pins on the board or in the connector to be burnt due to the high current flow. This can be easily rectified by soldering an earth and positive power supply wire directly in the place where the diode used to be NB
THE LEG CLOSER TOTHE BIG BLUE CONNECTOR IS POSITIVE AND THE LEG FURTHER AWAY FROM THE BIG BLUE CONNECTOR IS NEGATIVE

The reason why this happens is because the Zener Diode's function is to protect the sensitive logic circuits from voltage spikes by directing current to ground when the voltage exceeds the predetermined amount at the diode. A failed diode permanently lets current pass, which is your short.



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[Plex]

u get through with those pics?

[dlittlelion]

no boy pressure