Hands too large...
Join Date: Feb 2009
Location: South Africa
County: Northern Cape
You will need:
- three fast-switching N-channel MOSFET's with low on resistance, low gate charge and good avalanche characteristics, capable of delivering a continous drain current of +50A. I chose the SFP75N08R MOSFET's made by Winsemi (the originals was STP60NS04Z MOSFET's made by ST Microelectronics and was not available).
- one SCHOTTKY Diode (Rectifier) with a rating of 25A. I chose the MBR3045CT SCHOTTKY Rectifier made by International Rectifier (the original was MBR2545CT and was not available).
All four components are in the TO-220 package, with 3 longish legs, and a hole for bolting to the heat-sink.
In my case, only one MOSFET tested faulty, however I recommend that all four components be replaced, since:
- the test is done at ambient room temperature, while others may only show defects at higher operating temperatures.
- they are very cheap.
- their legs have to be snipped off to remove the heat-sinks, onto which they are bolted, making it difficult to resolder the legs and re-use the components.
The procedure for replacement is:
1) Once the ABS control module is removed from the car, open the lid by removing the retaining screws. This will expose two small arrow-head shaped aluminium heat-sinks, under which are the transistors.
2) Remove the retaining screw from each heat-sink, and lift one side of the heat-sinks upwards, bending the long spring-steel fingers (that are spot-welded to the transistor legs) to an angle of about 30 degrees. Using a small side-cutter, snip off the legs from the transistors, and remove the heat-sinks from the control unit.
3) Snip off the middle legs of two of the three new MOSFET's, and replace the old transistors with the new ones, taking careful note of their positions on the heat-sinks.
4) Bend the legs of the transistors to 90 degrees, and solder them to the spring-steel fingers.
5) Push down the head-sinks back to the original position in the control module, and replace their retaining screws.
6) Close the lid up, and re-fit the control module to the car, taking care not to damage the solenoid coils, and protruding copper tab (power feed to the pump). Re-fit all other parts removed for access.
7) Re-connect the battery negative terminal, and run all ABS actuator tests with FES, to verify that all is working properly.