Venturi Switch, no power help!

[n/a]

Hi Everyone (especially you Joe!) I still have that annoying rear end clunk upon final downshift coasting to a stop. I checked for power to the Venturi switch and am receiving power at the lower wire (red) wire but not at the upper wire (brown/white). When I trace the wires they disappear into a loom of many wires.  Is there a fuse that controls this switch somewhere, and if so where is it located? Or should I be looking elsewhere to source the brown/white wires short/no power? Right now, I am ready to source a new wiring harness for the engine compartment!  Help!

[ja17]

Hello James,
With the car in gear at idle the switch should be "closed" (power enters the switch on one terminal and leaves through the other). If you do not show power at both terminals in gear at idle then the switch is "open" not closing. The two 5mm allens which mount the switch can be loosened and the switch rotated until it closes (power to both terminals). Before making this adjustment you need to make sure the venturi linkage stop screw is not set incorrectly. This screw as mentioned must be set to hold the linkage so that the venturi flap just barely does not bind.
Some cars have an additional micro switch on the firewall which can be adjusted after the venturi is set up correctly.

In your case James adjusting the venturi and the venturi switch should solve the problem hopefully. Try disconnecting the dead wire and operate the switch to see if the power goes to the second terminal with the dead wire off. If you slightly advance the linkage the switch should "open" and not allow power through it. If you close it again power should be at both terminals. Keep us up to date!


Joe Alexander
Blacklick, Ohio

[n/a]

Thanks Joe, as usual you come through, thanks again!  Today, I adjusted the throttle plate first and then followed up with a linkage adjustement.  What a difference!  Car idles much better, no missing today. After doing this work, I noticed that I was getting small amounts of power to the formerly dead brown/white wire.  I pulled the venturi switch, and then cleaned all the contacts with a dremel tool and finished up with dielectric grease. I then would get full power to switch, but then it would fade as I tightened/adjusted switch with allen heads. I went through this scenario many times and then noticed that my venturi switch is cracked. I think that any pressure creates a short within which explains the weak/strong contact. Perhaps the venturi switch housing flexes from allen head pressure. Either way, it looks like I need a new switch. I am assuming that they are still available and very expensive?