North American Turbocoupe Organization



Mystery Wire Harness
jtucci Offline
Junior Member
#11
I just noticed this in one of your pics. Can you get a pic of everything under here? I wonder now if the brake work actually resulted in the removal of the prop valve.


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Jeff K Offline
Administrator
#12
Are those compression fittings in the brake line? I hope not, as compression fittings are NEVER supposed to be used to repair / splice brake lines.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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anasazi4st Offline
Senior Member
#13
(12-11-2020, 09:16 PM)Coupedaddy Wrote:   Anybody know where this one should be connected?  I was changing my oil and I found this one dangling loose right next to the filter.  Can't really tell where its coming from and can't see any obvious place where it should go.  Recently had major ABS master cylinder work done and the car has been offsite for the past year.  But everything that was working before is still working now, so I can’t tell if something has been disconnected or if this is a connection to some accessory my car never had.

I am almost 100% certain that it is the connector for the proportioning (prop) valve. I had my ABS unit out for a bit while I DIY repaired it last spring, and I have pictures of what that area looks like WITHOUT it in there. Looking at it, the only connectors that are close are the SPOUT and the prop valve, and you’ve already said the SPOUT has its little shorting plug, so it’s gotta be the other I would think.

If you look at jtucci’s second photo—underneath the non-ABS master cylinder (just to the left in the picture) you’ll see a white part with an orange plug connected to it. That is the prop valve. And, I would agree with him that the purpose of that electrical connector is to illuminate the red BRAKE lamp to warn of loss of braking capacity.

The only flaw in my reasoning is that, by design, that light should be ON—in your case, all the time, if it is in fact disconnected—when there is no signal, as a safeguard.

And, to your later question, it seems unlikely that the prop valve was removed, but certainly not out of the question.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 3 T5OD full rebuilds, 6 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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Jeff K Offline
Administrator
#14
Went out to the garage and had a look at my TC (20 deg F here this morning). That switch on the prop valve is the pressure switch that tells the PRC to switch to FIRM mode when brake system pressure exceeds 400 psi. My switch failed several years ago. Found one new one on Ebay, but the seller wanted something like $200 for it. NO WAY! Searched Mcmaster Carr (one of my favorite places to find weird electrical and mechanical components) for something similar and found an adjustable pressure switch I could adapt to work for $50. Required some adaptors and some brazing to get it to adapt to the fitting on the prop valve, and a different electrical connector but I got my auto switch to under hard braking FIRM back! Also, since the new pressure switch was adjustable, I was able to set the FIRM ride pressure to just where I wanted it.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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anasazi4st Offline
Senior Member
#15
(12-16-2020, 02:44 PM)Jeff K Wrote: Went out to the garage and had a look at my TC (20 deg F here this morning). That switch on the prop valve is the pressure switch that tells the PRC to switch to FIRM mode when brake system pressure exceeds 400 psi. My switch failed several years ago. Found one new one on Ebay, but the seller wanted something like $200 for it. NO WAY! Searched Mcmaster Carr (one of my favorite places to find weird electrical and mechanical components) for something similar and found an adjustable pressure switch I could adapt to work for $50. Required some adaptors and some brazing to get it to adapt to the fitting on the prop valve, and a different electrical connector but I got my auto switch to under hard braking FIRM back! Also, since the new pressure switch was adjustable, I was able to set the FIRM ride pressure to just where I wanted it.

Thanks Jeff! So that’s what it does! I wish we had a way to bookmark posts, it sounds like that’s a topic (what is it and what does it do?), that someone is going to be searching the Forum for in the future.

I will copy your response into my online Evernote Useful TC Notes for future reference.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 3 T5OD full rebuilds, 6 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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