Brake proportioning valve (Page 1/2)
Duck 1 FEB 06, 12:23 PM
Any way to free up the sliding valve part of this ? Is there a replacement valve for my 88 Fiero GT ?
theogre FEB 06, 12:41 PM
See my Cave, Combination Valve

The spool has 3 or more seals and doesn't move very easy to start.

The spool should return to normal to turn off the Brake Light when both circuits have full pressure again. May have to "pump the pedal" hard and a few times to "reset" the spool.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Duck 1 FEB 06, 03:33 PM
Thanks for getting back to me. I tried the pumping on brake pedal but nothing happened. I took the emergency brake handle apart and cleaned all parts, put it back together an still have red dash light Took the sensor wire connector wire off and still have red light. Is there a way to remove the internal spool valve to clean it ?
theogre FEB 06, 05:08 PM
⚠️ Warning: Do Not drive the car until fixed.

The Spool doesn't move w/o some problems w/ the brakes and you pushing the pedal to force it to move.
In most cars, you have to push pedal harder then normal braking to stop the car in light traffic.
You can't move the spool during most brake bleeding including "Pedal Method" that causes more problems.

If you did "Pedal Bleeding..." May have stuffed the MC secondary piston and turn on Fail switch because Front brakes are "dead" w/o leaking. IOW The MC is now F'd and B-light will stay On because the Combi spool is doing its job.
See my Cave, Bleeding MC notes & Quick Take-up notes

When that happens, the brake pedal and MC seems to work normal because rear brakes and MC primary still works and maybe you get some low pedal not like rear brakes w/ bad calipers.

--- Otherwise ---

Unplug what "sensor?"

You unplug the switch on the combi valve?
If so then your problem is Not the switch or spool but wiring or other problems.

You mess w/ P-brake lever...
Even if that switch works, P-brake hand lever won't shut off B-light unless have Cable Tension to pull the ratchet that operates the switch.
Get help so someone pull and release the P-brakes
Go in back of car and pull on main cable while helper release handle.

Or maybe close and just pulling the main cable can shut off the switch and light.


quote
Originally posted by Duck 1:
Is there a way to remove the internal spool valve to clean it ?

No. Taking apart a combi valve often causes more problems and must bleed all calipers after this and often those bleeders have frozen.

But You can remove the switch w/o causing problems because of 2 of seals on the spool. Pull the switch, plug in the wire to it, and light should still be off if is the spool has moved.

While very rare, the combi switch can fail or have other issues and keep light on.
Maybe Can see the notch in the spool too when switch is out.

⚠️ Warning: If you see liquid in the hole when the switch is out... Is likely the combi valve is trash and have to find good used one now.
Liquid is Water getting in thru the switch or B-fluid leaking out from same 2 seals letting you to remove the switch.

[This message has been edited by theogre (edited 02-06-2023).]

sanderson231 FEB 06, 09:08 PM

quote
Originally posted by Duck 1:

Thanks for getting back to me. I tried the pumping on brake pedal but nothing happened. I took the emergency brake handle apart and cleaned all parts, put it back together an still have red dash light Took the sensor wire connector wire off and still have red light. Is there a way to remove the internal spool valve to clean it ?



If you have unplugged the switch on the proportioning valve there are two possibilities; one is a ground in the wiring to the switch and two the parking brake switch is causing the brake light to illuminate. Plus if you remove the switch from the proportioning valve you should be able to see or feel the4 groove that the switch feeler rides in to verify that the shuttle is centered.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Duck 1 FEB 07, 08:45 AM
Thanks for all that information. I removed the valve switch and there was NO fluid of any kind. While I had the switch out I ran a continuity check on it and it checked out good. When removing the emergency brake assembly I noticed some light rust . I completely disassembled the brake handle and did a complete cleaning and light sanding. Using my multimeter I checked the green ground wire and switch operation which both checked good. With all visible checks performed , today I am going to refill the brake fluid reservoir, bleed the brakes again and try kicking the brake pedal to see if that will magically make that ##!%&*# red dash light go off , wish me luck, because I do not know what else to check !
Patrick FEB 07, 07:23 PM

quote
Originally posted by Duck 1:

I removed the valve switch and there was NO fluid of any kind.



Nor should there be.



Was the spool off-center, thus triggering the switch? If so, did you manually center it? I took mine apart years ago when I first got my '84. The previous owner had somehow got a small piece of rubber jammed in the spool of the combination valve.

[This message has been edited by Patrick (edited 02-07-2023).]

sanderson231 FEB 07, 10:05 PM
There are two switches that can cause the brake light to illuminate; 1) the proportioning valve switch and 2) the parking brake switch.

If you disconnect the proportioning valve switch and test the tan/wht wire with the ignition switch on you should see 12 volts. If there is not power at this wire then there is a ground in the wiring between the light and the connector (most likely place is the foil inside the receptacles for the wiring harness plugs to the instrument panel) and that will cause the brake warning light to stay on. If there is 12 volts at the connector then it points to the parking brake switch. I know from personal experience that it is possible for this switch to stay closed even if the emergency brake is released. Pull the connector and test the continuity through this switch with the parking brake released. It should be open. There could also be a ground in the wiring between the light and switch in this circuit.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Duck 1 FEB 09, 03:03 PM
Took the plug off of the pro. valve. Put a test light in the center hole and put the other test light wire against the other switch wire in the plug . There is no power getting to the por. valve switch plug. What is this foil you are talking about in the wiring harness and where exactly is it located ?
theogre FEB 09, 06:28 PM
The plugs for B-light should have "12v" when the I-key is on.
For Combi valve, just short the "pin" and light on. Plug in the switch when out of the valve should be Off until you push the tip.

Note: If have Power Lock for Rear Deck and manual transmission...
That uses P-brake wiring to work and if the relay have problems may keep the B-light On.
Find small relay under the dash and unplug it.
Same size & shape as Horn relay maybe dif color.