I know we got few EE here. I need some help.

I'm using a MSD window switch to provide a (-) ground for my nitrous solenoids. The MSD will provide (-) ground to the solenoids between the correct RPM range. This basically activeates the nitrous. The MSD can only handle 1.5 amp of draw. I believe the nitrous soleniods are drawing more. I need help wiring up a relay to provide (-) ground to the nitrous soleniod that's trigger by the MSD window switch's (-) ground signal wire.

Would this work.

30 - low amperage negative from MSD window switch.
85 - Constant +12V
87 - Ground
86 - To ground my nitrous solenoids
87A - Not used

 

I think you have 30 and 86 switched around...

You want the MSD to trigger the relay to supply the ground(- from source 87) to the solenoid. The 'trigger' to the relay should be either 85 or 86 to complete the circuit (both +/-)

Although you can wire 30 and 87 the way you did... it may be dangerous... if 87A grounds itself... your NOS will be activated!

I would reverse 30 and 87 also...

Summary:
30 - to Ground source to be supplied
85 - 12V
86 - MSD trigger (-)
87 - to NOS solenoid (the throw?)
87A- not used (default connection to 30)

 

OK...I called MSD and this is what they said.

85 - Switched +12.
86 - MSD (-) trigger wire.
87 - Nitrous relay / Soleniod ground ??? This doesn't sound right?
30 - Constant +12.

Chung, would the above work?
I think the first nitrous relay should be grounded and then get the +12V from the above relay 87. I'm so confused.

 

The Switched 12V at 85 is a good idea...
30 would cause your relay to send a +12V to the NOS relay/solenoid... is that what you want? I thought you wanted a ground sent?

 

I do want ground sent to my main nitrous relay to complete the circuit so it will activate my nitrous.

I believe MSD wants me to ground the main nitrous relay to the chasis. Wire the second relay to give +12V via the (-) signal from the MSD RPM switch to power the main nitrous relay.

I guess I either give +12V to the main nitrous relay or give (-) ground to the main nitrous relay.

 

Tony,
Check out my site for basic info on how relays work and how to use them. It's pretty simple and Chunger already answered most of the questions, but anyway..
http://www.geocities.com/bracecraig/maxima/relay.html

 

Thanks Chung and Craig. After looking at the diagram of the link and what Chung suggested, I understand more about relay now.