TAKdriver
Active Member
- Posts
- 621
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- Beside a field in Midlothian
There is a test to determine whether or not your ABS pump is working before you spend serious money on replacement. The fault might well be in the pressure switch alone.
Take a length of wire and earth it to the bolt holding down the battery clamp : bare the other end : remove the rubber sleeve from the connector to the pressure pump : jam the other end of the earth wire into the BLACK AND YELLOW wire in the pressure switch connector while it's in place : switch on ignition. If your pump fires up the problem is almost DEFINITELY in the pressure switch.
There are five wires going into the connector : BY goes back to the relay : BG goes back to the fusebox and is the + for the relay inside the pressure switch : BW goes back to the ECU and doesn't appear to go through the fusebox. The other two are blacks and they go to a common earth.
When I got the pump running by earthing BY it made me think ( not unreasonably) that the problem was a bad earth somewhere in the system. That resulted in futile weeks of tracking down and checking every earth.
I wrongly thought that earthing BY triggered the abs relay (17) . BY in fact goes through the fusebox and is in fact power going to the pressure switch which is earthed by one of the relays inside the pressure switch being closed by the pressure from the pump.
IF YOU EARTH THE BLAck/YELLOW WIRE AND YOUR PUMP RUNS THE PROBLEM IS DEFINITELY IN THE PRESSURE SWITH OR THE CONNECTOR. The connector wires are easily checked.
I suspect that an awful lot of perfectly functional ABS pumps have been replaced due to a faulty pressure switch. I have now had two out of three pressure switches faulty ( viz my original which went : the replacement which I assumed was OK and thirdly the scrapper which I put in as a last resort.)
You can also replace the pressure switch in situ by using a jubilee clip round it , tapping, slackening, tightening, tapping. Very little brake fluid comes out because the chamber that the pressure switch is going into is sealed by a diaghram which activates the plunger on the top of the pressure switch.
There's a million more things I could tell you that I got wrong before arriving here ! DON'T SCRAP YOUR ABS PUMP UNTIL YOU HAVE EARTHED B/Y TO FIND OUT IF THE ACTUAL PUMP PART FUNCTIONS
Pic 1 shows the abs pump complete
pic 2 shows the pump with pressure sweitch removed and sitting on top
pic 3 shows the rear of the connector where earth wire can be inserted.
Take a length of wire and earth it to the bolt holding down the battery clamp : bare the other end : remove the rubber sleeve from the connector to the pressure pump : jam the other end of the earth wire into the BLACK AND YELLOW wire in the pressure switch connector while it's in place : switch on ignition. If your pump fires up the problem is almost DEFINITELY in the pressure switch.
There are five wires going into the connector : BY goes back to the relay : BG goes back to the fusebox and is the + for the relay inside the pressure switch : BW goes back to the ECU and doesn't appear to go through the fusebox. The other two are blacks and they go to a common earth.
When I got the pump running by earthing BY it made me think ( not unreasonably) that the problem was a bad earth somewhere in the system. That resulted in futile weeks of tracking down and checking every earth.
I wrongly thought that earthing BY triggered the abs relay (17) . BY in fact goes through the fusebox and is in fact power going to the pressure switch which is earthed by one of the relays inside the pressure switch being closed by the pressure from the pump.
IF YOU EARTH THE BLAck/YELLOW WIRE AND YOUR PUMP RUNS THE PROBLEM IS DEFINITELY IN THE PRESSURE SWITH OR THE CONNECTOR. The connector wires are easily checked.
I suspect that an awful lot of perfectly functional ABS pumps have been replaced due to a faulty pressure switch. I have now had two out of three pressure switches faulty ( viz my original which went : the replacement which I assumed was OK and thirdly the scrapper which I put in as a last resort.)
You can also replace the pressure switch in situ by using a jubilee clip round it , tapping, slackening, tightening, tapping. Very little brake fluid comes out because the chamber that the pressure switch is going into is sealed by a diaghram which activates the plunger on the top of the pressure switch.
There's a million more things I could tell you that I got wrong before arriving here ! DON'T SCRAP YOUR ABS PUMP UNTIL YOU HAVE EARTHED B/Y TO FIND OUT IF THE ACTUAL PUMP PART FUNCTIONS
Pic 1 shows the abs pump complete
pic 2 shows the pump with pressure sweitch removed and sitting on top
pic 3 shows the rear of the connector where earth wire can be inserted.
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