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I'm trying to work through some vacuum issues on my car and have a question about one of the components in the system. The A/C Vacuum tank (engine compartment right beside the engine compartment light and relay box) has a couple of round switches (at least they appear to be switches of some sort) bolted to it. The lower switch is yellow and has one vacuum line running from it over to the intake manifold. If I put a vacuum gauge on this, I just suck air right through it -- it doesn't hold vacuum. First question, is this the way that this switch should function, or should it hold vacuum? Second question, what does this yellow switch, and the one above it for that matter, do?

many thanks,
kordon
 

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Re: Vacuum Answer on '83ZX

Kordon the two switches you ask about are magnet valves.

The lower switch is yellow and
> has one vacuum line running from it over to
> the intake manifold. If I put a vacuum gauge
> on this, I just suck air right through it --
> it doesn't hold vacuum.

The one with the yellow cap is for the FICD. (Fast Idle Control Device) Out of it should be coming a hose with a yellow stripe on it. It runs over to the manifold and connects to the FICD which is a round disk looking thing with a vacuum connection looking straight up. When the A/C compressor kicks on the wire to the yellow magnet valve is energized and the magnet valve supplies vacuum from the tank to the FICD. This in turn increases the engine speed. The only time vacuum should be going through this valve is when the A/C compressor is on.

First question, is
> this the way that this switch should
> function, or should it hold vacuum?

If you connect a vacuum gauge to the yellow capped valve, you should get no vacuum reading until the A/C compressor kicks on. If you want to test the valve one easy way to do it is to disconnect the wire to it and see if it won't let vacuum through.

Second
> question, what does this yellow switch, and
> the one above it for that matter, do?

The other magnet valve, the one with the black cap, is for the heater. When you turn the selector switch to any position but off (low, auto, high, etc) power should be applied (through the blower relay) to the wire going to this valve and should open the line to the vacuum tank and supply vacuum to the heater doors (and water valve if auto temp control).

There are two more lines coming out of the tank. One supplies vacuum from the manifold to the tank. This line should have a white stripe on it. The other line goes directly into the cabin and supplies vacuum to the auto temp controls.

At least that's how I remember it. If you still have trouble let me know and I'll dig out my diagrams.

Bob A.

> many thanks,
> kordon
 
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