Vacuum Pump Relay Help

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=45559
Printed Date: July 07, 2025 at 4:49 PM

Topic: Vacuum Pump Relay Help

Posted By: Carnalsupply
Subject: Vacuum Pump Relay Help
Date Posted: December 19, 2004 at 9:21 PM

I have a '70 Corvette and have installed an electric vacuum pump to run my headlight and windshield wiper doors, but I am a REAL NOVICE at electrical, and am having difficulty wiring the vacuum pump, relay, and pressure switch correctly. The pump needs to run when the ignition is switched on, but at this time it isn't. In fact, when I used a test light to verify the relay was receiving power, the ground of the test light actually started the pump running, so I obviously have a problem.

Thanks,

Carnalsupply

Replies:

Posted By: KarTuneMan
Date Posted: December 19, 2004 at 11:29 PM

how is your relay wired.... ? What type of wire is going to what pin on the relay (voltage ground etc)

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Posted By: Carnalsupply
Date Posted: December 20, 2004 at 11:31 AM

#30 is connected to the Pressure Switch

#85 is "pigtailed" to the fused 12V source and the + side of the pump

#86 is grounded

#87 is connected to the - side of the pump

As it turns out, my touching the test light to the #85 post and making the pump start running might just be a tell-tale sign the pressure switch is bad (according to a friend), so he advised me to go home, power up the system and ground the pressure switch (at the top, above it's insulation ring), and if the pump starts running the pressure switch is bad.

I SURE wish I had known that before!!!!!!

Thanks for the input/help, it's MUCH appreciated!

Carnalsupply