RRC brake failure

went to drive to work this morning and found that the brakes didnt work..

-the pedal feels normal
-there are no obvious leaks anywhere under the bonnet
-the pump doesnt come on with the ignition like it usualy does

so im thinking this is an electrical problem rather than mechanical? i had a multimeter on what i assume is the pump power supply and it didnt show any signs of life.

car is a '90 RRC vogue se 3.9

any ideas?

thanks,

tom

I don't have a wiring diagram for a '90. They seem to jump from '88 to '92. The '88 doesn't have ABS. The '92 diagram shows the pump being fed from fuse F4 in the ABS fuse block through a relay K102. I think both of these are under the left hand front seat.
Hope this may help.

would the fuses and relays under the seat be labelled? i took the side panel off the seat but could only find 3 fuses under there, none of which were labelled (not clearly anyway) and none of them were blown.

Don't know to be honest. I can't check mine as I'm not at home and won't be for a couple of weeks yet.
F1 feeds the supply for the ABS Load relay K101 and then the ECU
F2 feeds the ECU
F3 feeds the ABS pump relay coil K102 which is earthed via the ABS pressure switch unit
F4 feeds the ABS Pump itself via the K102
Remember this is for a '92. I'm assuming the '90 should be the same or very similar. maybe the 4th fuse is somewhere else under the seat. You'll need to identify the relay K102 to see if that's energising when you switch the ignition on. When you say you had a meter on the pump power supply, where were you measuring that?

must be something in the air, my light came on today for the first time ever.

it went out for the next two drives so I am praying it doesnt come back on!

i measured it at the plug right next to the pump itself under the bonnet (the power leads that is, not the multiplug that plugs directly into the pump unit)

and oddly i didnt get any warning lights at all on the dash =/

Looks like you have to do a bit of fault finding then working backwards from that connector. Next back is the relay K102. If you can find this under the passenger seat, you need to check for power into the relay base on pin 30 (from fuse F4) which should be a brown and orange wire and power out if the relay is operating on pin 87 which should be a brown and red wire. The power to operate the relay come from F3 on a white and red wire onto pin 86 and goes out on pin 85 to the ABS pressure switch unit on a white and blue wire. The other side of the pressure switch is to earth.
I have a very handy tool I got years ago from Snap-On. It's basically a test light that has a hook at the bottom and a retractible pin that you push down on the wire. The tool has an earth lead you clip onto any convenient bear metal. Pressing down on the pin causes it to go through the insulation onto the wire itself. If it's live, the tool then lights up. Very quick and easy way of testing for live wires without trying to prod into terminals where quite often there is no room anyway. I'm sure Halfords or Sealey etc will do something similar now. It was only a few quid then and it's paid for itself a hundred times over.

thanks for the replies, but it seems to have started working again =/
seems its doing what late 80's and early 90's british cars are best at... intermittent electrical faults...
if (when) it fails again i will try what you said above and hopefully find the source of the problem.

thanks again,

Tom

Then be ready for it and find and buy one of those circuit testers!
Sealey

yeah that looks like a pretty good investment.

im not sure whether to chance it with driving the car now, because it didnt come up with any warning lights when the brakes failed this time, im slightly concerned that they could fail again without warning. i was just lucky that i was travelling about 2mph when i noticed it had no brakes last time.

should there be an ABS light that comes up with the ignition like there are in all the other cars with ABS ive had?

yup, two

excellent... how worried should i be about using my car? =/

actually thinking about it there is a light that comes on when i crank the engine then goes out again when it fires (doesnt come on with the ignition though, only when i actually crank it); its an orange one showing a circle surrounded by another ring of dashes, which i guess would be pad wear sensor?

im guessing there should also be an ABS light that comes up?

what year is yours? mine are red and opposite each other, come on when you start the car and go out at 7mph

mines a 1990 Vogue SE. the only lights i have when the ignition is on are the battery light, engine oil light, and the parking brake light (this never goes out, dodgy sensor i think)

and the pad wear light (im assming thats what it is) only comes on when you crank it, then goes out as soon as it fires

mmmmm I think the lights your calling pad wear and parking brake lights are the ones I mean and they are not behaving for you

oh right, is there no light specifically for the ABS system? every other ABS equipped car ive had has had abn ABS warning light come on with the ignition then go out after the engine has been running a few seconds. what do all the lights that you get look like?

EDIT: just been out to have another tinker under the bonnet, while the brakes are working the same as they have been up until this incident the other day...

1. the power supply to the pump now reads a healthy 11.5something volts
2. when i unplugged the multiplug connected to the pump itself the light on the dash that i thought was just for the handbrake went out

so i guess the handbrake light is actually the ABS light aswell, but i dont know what to do now.
also its worth mentioning that my ABS has never worked, so i just assumed my car didnt have ABS fitted. it was only when i went hunting under the passenger seat for fuses that i found the ABS control box...
so my ABS system is boned, but the brakes themselves work fine, but because the ABS light is always on whether or not the basic braking system is working i cant tell whether or not the basic system has failed again until the car just fails to stop....
:frusty:

any ideas?

the light is on because its not working at all!!

You want the light out after you go over 7 mph form each startup.

I dont know alot about abs as I have had no probs till my light came on briefly this week but it went out and hasnt come back so I am not worried.

I know a man who can fix it for you, he is a mobile landy specialist. he is busy but he can sort it easy. PM me if you want his number.

Also khryztal on here has had some fun with his, although his light was on the other day so I am not sure if his fix worked but PM him, tell him Fett sent you and that hes a cnut

yeah i realise that the light is on because the ABS is ****ed, i was just kind of hoping someone else may have had this problem before and be able to tell me exactly whats wrong, how to fix it, and that it wont cost more than about 34p (for that is my entire worldly wealth at the moment...) to repair.

possibly wishful thinking

Most likely a wheel sensor, either incorrect air gap or wheel bearing/ sensor.

Early disco's/classics you can blink fault code