Parking Brake Switch Problems

[Daveo91Burb]

Parking brake light stays lit and works fine when parking brake is applied, but when p-brake is off, driving down the road, idling, key just on, etc. the light flickers. Constantly. How does this thing work? It seems like a bad ground - does something get grounded when the brake is off to turn off the light?

 

[Cuba]

The ratchet mechanism depresses a switch and grounds it. It's in the driver footwell under the steeringcolumn.
1.The switch may be bent a little to where it's still making contact.
2. The parking cable or the return springs (at the ratchet mechanism or at the drums) could be too lax to where it's allowing for intermittent contact.
3. Fluid level in the reservoir could be getting low & when driving shifting the fluid enough to activate the light.

 

[yevgenievich]

It could be the rwal system blinking

 

[bucket]

It could be the rwal system blinking

That flashes in a sequence though, not really a flicker. I guess it really depends on what Dave considers to be a flicker.

 

[Daveo91Burb]

It's very erratic, definitely not a sequence. It has all the hallmarks of a loose or bad ground so that's where I'll start. (Thank goodness as I'm sure the RWAL system is loads of fun to diagnose). Thanks for the help everyone!


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[bucket]

IIRC, you can simply unplug the ABS control module and it completely defeats it, including turning the flashing light off. I realize that this info does no good right now, but maybe in the future.

 

[Daveo91Burb]

IIRC, you can simply unplug the ABS control module and it completely defeats it, including turning the flashing light off. I realize that this info does no good right now, but maybe in the future.

Well maybe not so far in the future.... I looked at the flashing more closely and it is flashing a sequence - 4 short and one long. I think Viktor may have been correct.

So I unplugged the top connector on the controller by the m/c - blinking stopped. Then I plugged it back in and the light seemed to reset - now it's off when it should be but I didn't drive it yet. We'll see maybe I'll get lucky? What is it that usually fails on those systems, the controller?


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[yevgenievich]

This is the link I use for reference
http://www.aa1car.com/library/abs_kelseyhayes_rwal.htm

I have not been able to find a source for new replacement parts for the rwal system yet. But have not looked too hard. Mine has an intermitent indication that started after blowing rear wheel cylinders out during the Elk on the road accident.

 

[chengny]

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[Daveo91Burb]

Thanks, guys. This may take a while to diagnose, but now it's not doing anything wrong. I drove it today and light behaved properly - brakes did too. Dumb question: the PO replaced the rear-end with a 14 bolt FF from a '77 Burb. That wouldn't cause any problems with the RWAL would it?

 

[chengny]

Thanks, guys. This may take a while to diagnose, but now it's not doing anything wrong. I drove it today and light behaved properly - brakes did too. Dumb question: the PO replaced the rear-end with a 14 bolt FF from a '77 Burb. That wouldn't cause any problems with the RWAL would it?

Yeah, in some cases it would. The VSS (vehicle speed sensor) is mounted on the transmission and provides the DRAC with a pulsed signal that tracks up/down with road speed. The DRAC takes that AC sine wave input and converts it to a DC square wave output which is then sent to the ECU.

If the final drivetrain is altered (e.g. by changing the axle ratio or installing different sized tires), the ECU will then receive a skewed road speed input. And it will get all pissed off.

But in your situation (4WD), it is doubtful that the PO would have used a rear gear set with a different ratio - unless he also changed the front axle to match the rear. That would only leave off-sized tires to confuse the ECU. You could just revert to the stock size.

Either that or install the correct DRAC for that axle ration. The VSS is not an issue - it is standard across the line.

 

[yevgenievich]

If your spedo is accurate, not an issue. If spedo is off, get a soldering iron out and change the jumpers on the drac. Non of the online calculators are exactly correct that I could find. I had to play with jumpers a bit to get correct speed before

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[Daveo91Burb]

But in your situation (4WD), it is doubtful that the PO would have used a rear gear set with a different ratio - unless he also changed the front axle to match the rear. That would only leave off-sized tires to confuse the ECU. You could just revert to the stock size.

He used both front and rear axles from the '77 - went from 3.73s to 4.10s. However, the speedo is pretty close in checking with GPS, 1-2 mph off only. So maybe he did that part right. And I took it camping for the last several days and no issues at all. Maybe the reset by unplugging the connector was all it needed. Thanks again for the help.

 

[chengny]

He used both front and rear axles from the '77 - went from 3.73s to 4.10s. However, the speedo is pretty close in checking with GPS, 1-2 mph off only. So maybe he did that part right. And I took it camping for the last several days and no issues at all. Maybe the reset by unplugging the connector was all it needed. Thanks again for the help.

It's very erratic, definitely not a sequence. It has all the hallmarks of a loose or bad ground so that's where I'll start.

We may have gone off on a wild goose chase with the whole RWAL thing. Should've listened to Mr. Cuba's thoughts on the subject and checked those first - specifically no. 2 below:

The ratchet mechanism depresses a switch and grounds it. It's in the driver footwell under the steeringcolumn.
1.The switch may be bent a little to where it's still making contact.
2. The parking cable or the return springs (at the ratchet mechanism or at the drums) could be too lax to where it's allowing for intermittent contact.
3. Fluid level in the reservoir could be getting low & when driving shifting the fluid enough to activate the light.

If it happens again, lift up on the e-brake pedal with your toe. If the light goes out...that's all it is.

 

[Daveo91Burb]

No, I don't think it was a wild goose chase. True, I did think it was erratic at first but in a later post I corrected that and said there was a pattern: four short and one long. (The short blinks are very short so it looked at first like a bad ground but definitely now see a repeating pattern). And the blinks stopped by unplugging the RWAL connector at the M/C so I'm pretty sure it was related. And when it was blinking I did mess around with the pedal a fair amount with no change. My worry now is what happens when unplugging and reconnecting the connector doesn't work but I'll cross that one when I come to it. For now - no issues....


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