Car is a 1993 (Phase 2) 405 1.9TD estate, with the later-type ABS.
Last week, during torrential rain, I noticed the brake pedal seemed hard and the brakes rather "grabby". The ABS warning light was not lit. When I got home, I switched off the car - but continued to hear a rapid "ticking" noise from the under the bonnet.
The source of the noise is the electrical box next to the ABS pump, at the front offside of the engine bay behind the headlight. There are three electrical plugs to this box - a 3 pin, 5 pin and 6 pin. Unplugging the 3 pin stops the noise - but of course this puts on the ABS warning light. However, the brake pedal now feels normal (i.e. not hard), and the brakes apply evenly.
Looking at Autodata, it appears that the 3-pin plug is power to the pump.
I've suffered this once before - when I bought the car two years ago, and got a bit over-zealous with an underbonnet clean. Drying it out solved the problem.
Today I inspected the connections. The 3-pin socket on the black box looked pretty manky - lots of green gunge (copper sulphate?) which I cleaned out with electrical contact cleaner and paper towel.
However, now it's all clean and dry the problem persists - putting the 3-pin plug back on the connector brings back the ticking noise. Being an electrical dunce, I have no idea how to proceed, and am reticent to throw £££'s at the car really.
Any ideas from the learned members of the forum? Can this box be easily removed? Also, I assume the ABS ECU is sited elsewhere - is it up near the pollen filter on the scuttle?
405 - ABS pump continually on?
Moderator: RichardW
405 - ABS pump continually on?
'93 405 Hunter TD estate
Hi -
It wont be the ABS system thats playing up.
The ABS has only one purpose in life : to prevent the brakes from working, i.e. releasing the brakes on one or more wheels to prevent the wheels from blocking.
Its the vacuum pump for the vacuum power assist for the brakes thats playing up on you.
When the vacuum is not present (pump not working), you will instantly feel the lack of power assist, by the hard brake pedal : you will have to provide all the brakes effort yourself.
I'd say you should give it one more try before reverting to the garage.
1) disconnect the battery negative terminal (important !)
2) the power connector you already have tried to clean out, must further be polished down to clean metal on the maiting pins.
This is a tedious job, but its exactly where the big savings are hidden.
If you can clean up the contact pins, ensuring good electric connections, there is a 98% chance you are on the road again soon.
Use a tiny nail file, even a tiny drill, that will rub clean the metal by the sharp edges.
3) one part of the contact set will have any kind of a spring action to clamp well on its counterpart.
Try strengthen up this spring action using strong needles or whatever that does the trick.
Once clean and tested, you may smear with some vaselin for water protection.
It wont be the ABS system thats playing up.
The ABS has only one purpose in life : to prevent the brakes from working, i.e. releasing the brakes on one or more wheels to prevent the wheels from blocking.
Its the vacuum pump for the vacuum power assist for the brakes thats playing up on you.
When the vacuum is not present (pump not working), you will instantly feel the lack of power assist, by the hard brake pedal : you will have to provide all the brakes effort yourself.
I'd say you should give it one more try before reverting to the garage.
1) disconnect the battery negative terminal (important !)
2) the power connector you already have tried to clean out, must further be polished down to clean metal on the maiting pins.
This is a tedious job, but its exactly where the big savings are hidden.
If you can clean up the contact pins, ensuring good electric connections, there is a 98% chance you are on the road again soon.
Use a tiny nail file, even a tiny drill, that will rub clean the metal by the sharp edges.
3) one part of the contact set will have any kind of a spring action to clamp well on its counterpart.
Try strengthen up this spring action using strong needles or whatever that does the trick.
Once clean and tested, you may smear with some vaselin for water protection.
Anders (DK) - '90 BX16Image
Thanks for your advice, Anders. It's not too bad to clean up the socket on the electrical control box, although there still appears to be a little green gunge at the bottom. It's quite tricky to get any sandpaper in there, so I might see if I can find a nail file or similar to do it.
The contact with the spring action (the plug) is very difficult to get at - I am already concerned that one of the three sprung connectors is becoming bent. It's a shame the plug cannot be dismantled - and may be where the problem lies. I think this pin provides the signal to the ABS pump (I don't have Autodata on this computer - but I am sure the other two pins provide 12V and ground).
I am pretty sure the vacuum pump is OK - the pedal goes hard with the ABS pump working all the time. Removing the ABS fuse reverts back to a softer pedal.
Could there be a problem with the ABS ECU, sending a signal for constant need for ABS to the pump perhaps, or a relay to do same?
Richard
The contact with the spring action (the plug) is very difficult to get at - I am already concerned that one of the three sprung connectors is becoming bent. It's a shame the plug cannot be dismantled - and may be where the problem lies. I think this pin provides the signal to the ABS pump (I don't have Autodata on this computer - but I am sure the other two pins provide 12V and ground).
I am pretty sure the vacuum pump is OK - the pedal goes hard with the ABS pump working all the time. Removing the ABS fuse reverts back to a softer pedal.
Could there be a problem with the ABS ECU, sending a signal for constant need for ABS to the pump perhaps, or a relay to do same?
Richard
'93 405 Hunter TD estate
I've now cleaned up the connections with a nail file, and been out with a multimeter.
It appears that the modulator has the right internal resistance, however the 3 pins on the power plug give 12v for pin 1, 0 for pin 2 and 12v for pin 3.
Looking at Autodata, it appears pin 2 is ground and pin 3 is live feed, so that would make sense - I assume that pin 1 provides the voltage to operate the modulator.
Very confusing, as if the system is all connected up, the ABS warning lamp goes through it's self-test when the ignition is turned on (3 flashes)...then goes out, indicating normal ABS operation!
There has to be some reason why it's getting voltage to operate all the time, damned if I can work out why...perhaps the relay - is there one, I wonder? I have no idea where it is...
It appears that the modulator has the right internal resistance, however the 3 pins on the power plug give 12v for pin 1, 0 for pin 2 and 12v for pin 3.
Looking at Autodata, it appears pin 2 is ground and pin 3 is live feed, so that would make sense - I assume that pin 1 provides the voltage to operate the modulator.
Very confusing, as if the system is all connected up, the ABS warning lamp goes through it's self-test when the ignition is turned on (3 flashes)...then goes out, indicating normal ABS operation!
There has to be some reason why it's getting voltage to operate all the time, damned if I can work out why...perhaps the relay - is there one, I wonder? I have no idea where it is...
'93 405 Hunter TD estate
I managed to get hold of an ABS modulator from a scrapped car for £50, and after fitting this today (a fun job, I must say) the ABS is back to normal. So I suspect that a relay within the sealed electronics box had given up the ghost on my original one.
A decent brake pipe spanner is essential for getting the unions out of the modulator, though.
A decent brake pipe spanner is essential for getting the unions out of the modulator, though.
'93 405 Hunter TD estate