What is this thing?

[RustyRecycledT]

Brother in law was working on his '92cc and found this thing. neither of us has any idea what it is or does. ford dealership doesn't show it in their diagrams of the vac system. It's tied into the vac block. it's located in the area of the drivers inner fender. In the picture it's the hockey puck looking thing with one vac line and some electrics coming out of it.

Anybody have any idea what this thing is and what it's for?

here's to hoping.......

 

[Silver91Hatch]

Low vacuum warning switch?

 

[icanfixall]

Thats what it is. Most of them don't work... At least mine doesn't work. Someday I may fix it but running the hydroboost brake system I don't care what the vacuum is doing anymore...

 

[smolkin]

Yeah, on my truck the "low vacuum warning" is when all of the sudden I have no brake boost and no gears except 1st.
Pretty silly I think since I'm either gonna have vac or not; do I need a light to let me know I can't stop and can't go more than 10mph?

 

[OLDBULL8]

If your not an Idiot, you don't need it. You know IDIOT LIGHTS

 

[RustyRecycledT]

thanks guys!

I'll let him know what it is. seems kind of redundant to me though. When I lost vacuum on my '86 I knew it because the brakes were nearly non-op.

 

[TWeatherford]

Cool, I was wondering the same thing a while ago. Never got around to asking though. I broke the plastic fitting on the side of it, so I carefully jb welded it back on. If I'd a known I would have just plugged it. Mine doesn't work, no low vacuum light came on when I broke my serpentine belt...

 

[MIDNIGHT RIDER]

Yes, that be the low vacuum switch.

You can test it for continuity when the engine is not running to see if the switch is good.

If it is a dud, that hose is a good place to connect your in-dash vacuum gauge.

If the low vacuum light actually works, then you can just TEE that line for the gauge.

I have two vacuum gauges, one for the truck and one for the trailer.

I need one of those switches that works so that I can connect a low vacuum warning buzzer to my trailer system, such that the buzzer sounds when the vacuum is low, more for the factor than any other reason, sort of like the low air buzzer on a big truck.

 

[Agnem]

For those wondering, it triggers at about 10 hg. All of mine work. You can test yours with the motor running, trans in neutral and parking brake RELEASED (block your wheels) by just pulling the fuel shutoff solenoid wire off to kill the engine, then just get in and pump your brakes until the pedal gets hard. The brake light will come on if everything is correct. I suggest doing it that way, instead of just setting the ignition to on and doing the same thing. Your glow plugs will suffer doing the test that way. If your smart, you've already installed a vacuum gauge as part of your standard instrumentation, as when this light comes on, it is really too late to stop anyway.

 

[LCAM-01XA]

Mine was dead too, I lost the vac pump once and the light never came on. Since I converted to hydroboost I've removed the darn thing, cut its harness, and use one of the wires for powering my recirculation door solenoid, and the other I use to trigger my auto-lights control module...

 

[gatorman21218]

theres a low vaccum light??? well i guess mine doesnt work either

 

[LCAM-01XA]

It ain't a designated low-vacuum light, it's just the red "brake" light that comes on when you put the parking brake on - basically the light gets key-on power from the cluster, and both the e-brake switch and the low-vacuum switch can ground it to complete the circuit and make the light come on.

 

[Sycostang67]

I spotted this in my engine compartment the other day and was curious about it's function as well. Good timing on the post.