pressure switch on ABS pump module

Gilles · #1 (**permalink**) 12-26-2006, 01:20 PM

yes, my yellow light came on and I already bleed the brakes and topped the reservoir (like on the past) but this time the light remains on.

Do you have to bleed the brakes again afret replacing the pressure switch that is located next to the electric pump or just depressurizing the sistem will do?

After bleeding the brakes they feel great and firm but once you start moving (and after a couple of times of using the brake) the light comes on again.

Thanks, Gilles

**AR4me** · #2 (**permalink**) 12-26-2006, 03:01 PM

Gilles,
Check your wheel speed sensors. Verify that they are in the right range (look up in the manual, though I believe 1000 Ohm is the right ball park). This is the most typical cause for the orange light coming on once vehicle starts to move.
Jes

andrewg · #3 (**permalink**) 12-26-2006, 04:13 PM

When the light comes on does the pedal get soft? Can you lockup the brakes?

Gilles · #4 (**permalink**) 12-27-2006, 03:21 PM

Ok, yesterday while driving home the light did not came on until right before getting home and this morning was off all the way, (these are the good news)

However, early this morning I was going very slow (5-10mph), slightly applied the brake and the pedal jumped back against my foot. This was not the first time, but it did it on very seldom occasions.

At lunch time it did it several times and on one occasion it felt first like the front left caliper got stuck for a moment before the pedal jumped back up again

Could a sticking caliper cause this? Or more like a failing master cylinder

Thank you, Gilles

**AR4me** · #5 (**permalink**) 12-27-2006, 03:34 PM

Gilles,
It could still be a wheel speed sensor issue. Not necessarily the sensor itself. It could be loose (warn) front wheel bearings causing the gap (between sensor and ring gear) to vary as load on the wheel changes. Try jack up the front and check for play in front wheel bearings. Also, is the light coming on, or the kick-back, correlated with turning a particular direction, or hitting a particular road uneveness?
Jes

loach1 · #6 (**permalink**) 12-27-2006, 03:59 PM

I have had the pedal kick back problem, both times cured by a new accumulator. The first new accumulator didn't last long at all and may be OK, perhaps the system just needed a good bleed which came with the new accumulator.

I've never had a sticking caliper feeling, though. Just wanted to let you know that pedal kick-back is probably just a pressure problem. The stuck caliper may be unrelated and caused by the master or caliper, but probably not a control problem since the ABS only releases pressure and cannot keep it applied unless your foot tells it to.

If it was my car, if the accumulator is original, I'd replace it along with a good bleed and hope for the best.

Gilles · #7 (**permalink**) 12-27-2006, 06:24 PM

Loach,
I installed a new accumulator a little more than a year ago
However, I have a spare accumulator that I can use for testing, they are not really that hard to install but they are a little pricey, the one I bought was a GM (not AR OEM).

AR4ME, I installed new bearings about 12-15 months ago, I will check if one of them is loose

Gilles

loach1 · #8 (**permalink**) 12-27-2006, 07:08 PM

Another suggestion:

To determine if it is an ABS control problem or a brake pressure problem, disconnect a wheel sensor and the ABS controller will go off-line, your ABS light will be on but you will have conventional braking. If your symptoms persist then you will know that they are on the hydraulic side rather than something screwy with the sensing/pressure relieving side of the system.

andrewg · #9 (**permalink**) 12-28-2006, 06:08 AM

I agree that is sounds like a pressure problem not a sensor problem. I have never had a caliper stick that caused what you talking about. I like the idea of determining what side of the system it is.

Gilles · #10 (**permalink**) 12-28-2006, 08:16 AM

Actually I had two different issues, the light and the pedal kick back
The wheel bearings where ok, I noticed that the wheel sensor cable was too tight against the body (at the grommet) so I give it some slack, and this morning the light was off, hopefully it will stay off :-)

For the pedal kick back issue, I noticed that right after the pedal kicks back, when you push down it makes a slight noise (and feels) like something is rubbing / dragging at the master cylinder.

After replacing the accumulator with a spare one I will advise if there is some change or improovement. I do appreciate your comments and suggestions, thank you.
Gilles

sgmhz · #11 (**permalink**) 01-03-2007, 04:04 PM

Is there a test procedure for the abs pressure switch? Is there a pin out for the connectors so I know which one is which switch / ground?

I suspect my pressure switch is bad. I can hardwire the abs pump and it will run, but the pump relay doesn't close so no power goes to the pump.

Can the pressure switch be separately replaced? Where would I find one?

Thanks a lot.

loach1 · #12 (**permalink**) 01-03-2007, 04:15 PM

If I remember correctly the factory manual troubleshooting guide has the pin-outs in it. I have a new pressure switch from a Reatta pump that (again, if I remember correctly), the same connector on it. I chose to re-use my Milano switch just in case the pressures were different. If you want to give it a try, let me know and I will mail to you.

sgmhz · #13 (**permalink**) 01-03-2007, 06:44 PM

Thanks for the info. I have been using the wrong manual (there is the craigs version and I guess alfa75.info version.) I have now found the section with the pin out.

I will check the switch with a multi-meter tomorrow and let you know.

andrewg · #14 (**permalink**) 01-03-2007, 09:34 PM

The Reatta switch is different and can not be used for the Milano application.

**AR4me** · #15 (**permalink**) 01-04-2007, 12:50 AM

Quote:

The Reatta switch is different and can not be used for the Milano application.