What triggers the brake warning dash light?

[RustyBucket]

I've been noticing the brake light on my dash has been coming on recently and I haven't been able to figure out why. The brake fluid level is fine and the brakes are working normally. The car stops normally with no unusual pedal feel.

It's usually been doing it on cold mornings and it goes away once the car warms up. Yesterday, however, it went off when I disengaged the parking brake but then came back on about a minute later. Today, it came on briefly under hard uphill acceleration but then went away almost right afterward.

My first suspicion is the parking brake switch, but I haven't been able to test it while the light on the dash has been acting up. The fact that the light went out after disengaging the parking brake but then came back shortly afterward makes me wonder if it is something else. The connector to the low fluid level sensor on the master cylinder is seated properly.

I remember when I had problems with the alternator wire on my old Pulsar, the brake warning light came on when the voltage was low. I see that the alternator connects to the brake warning light on the G50 as well. I checked the battery voltage both at idle and with the car off and the voltage was definitely not low; around 14V at idle and 13 with the car off. According to the FSM, the regulated output voltage of the alternator should be 14.1-14.7V (EL-17).

Any ideas NICO?

[goody90q45]

What you're describing happened to me when I had the alternator on my first 90Q replaced with aftermarket. The battery never discharged but the brake light coming on under load was very annoying, especially at night.

Have you replaced the alternator?

[Q451990]

Check your brake fluid and make sure both chambers are filled to the full line. The fluid tank is partitioned so the front or rear will still work if one set looses fluid. The alternator will typically make the ABS light flicker with it too.

Heath

[StevieRaySTL]

-- Ive been having the same problem, it's really cold here right now. Going to check it out today.

[maxnix]

Brake Fluid level or Alternator/Battery or pad sensors.

[RustyBucket]

StevieRay, how did your battery terminals look when you checked out your Q?

I cleaned off and re-seated my battery terminals today since there was quite a bit of corrosion build-up on the negative terminal. I'm hoping that was the cause of the light, so I'll be keeping my eye on the light to see if it comes back.

Check your brake fluid and make sure both chambers are filled to the full line. The fluid tank is partitioned so the front or rear will still work if one set looses fluid. The alternator will typically make the ABS light flicker with it too.
Heath

I should go out and get some brake fluid to top it off or, if I find the time, change out my brake fluid. It kind of looks like it could use a change. Wouldn't you notice a difference in pedal feel if you were low on fluid in one of the chambers though?

Have you replaced the alternator?

I've never replaced the alternator and I have not seen any indication of it being replaced since 2005 which is as far back as the receipts from the PO go. Lino told me that my alternator looks OEM, possibly original because of the green painted stator. If it's original it's 17 years old with 280,000KM on it (about 174,000 mi).

Brake Fluid level or Alternator/Battery or pad sensors.

I think you're mistaken on the last item on that list. The pad sensors are connected to the multi-function display. It's just the parking brake, low fluid level and alternator connected to the light, according to page EL-43 of the 1994 FSM.

[96Qowner]

It happens to mine every fall when it gets cold. It's always low fluid - a very sensitive sensor. Just top off your fluid.

[StevieRaySTL]

-- My battery terminals are good... Turns out my float was stuck.

[Q451990]

Interesting... I have never heard of that before!

Heath

[qship96]

What condition/color is the brake fluid? I have seen some scummy looking brake fluid in master cylinders that actually looked like it had algae/mold growth due to owners not changing it!

[Infinitiguy19]

After having the ABS actuator and Master Cylinder (MC) replaced I will bleed the system frequently. I mean it is stupid simple to bleed the ABS Actuator and the calipers are not that bad either.

One should think things are impossible to accomplish then find out how easy it is to do. It really is a good feeling being wrong like that.

[RustyBucket]

I topped up my brake fluid over the weekend and I haven't seen the light come back. I guess it was low after all

I've been meaning to change my brake fluid for a while, I think it could use a change.

[maxnix]

Every two years will save you future ABS problems. Use DOT 4.

[q45ness]

Can you take the leads from one sensor and run it to another sensor so that two connections are on one sensor to make the abs tcs light go out on the dash? I don't see any reason why not, other than I do not see any threads about it. Please let me know if this is doable on the rear brakes. I know it will change the ohms with two leads going to one sensor, but will it clear the light?