Amp Draw

[bruce69camaro]

I hooked up my NOS system this weekend and melted two micro switches and can't figure out why,
except now I'm thinking the switches I have are not rated for the correct amperage.

I'm using a relay and use the micro switch to make the ground on the relay and each time I close the micro switch, it melts.

What amp switch should I be using? I'm using cheater system solenoids which I believe are 10 amps? Thanks, Bruce

[Danny Cabral]

I'm using a relay and use the micro switch to make the ground on the relay and each time I close the micro switch, it melts.

You must not have the micro switch wired to the relay correctly, or you have a short circuit.
If the micro switch triggers the relay's coil, there shouldn't be any load on the micro switch at all.
It seems you somehow have the N2O solenoid's amperage draw going through the micro switch.

[bruce69camaro]

I've been picking my mind on this. I'm using SPDT relay, #30 goes to battery, #87 goes to solenoids, then to ground, #86 goes to arming switch, #85 goes to micro switch then to ground. I'm going to double check my wiring and then make sure the relay isn't bad. Thanks.

[440roadrunner]

Some of those relays have a diode across the coil. This is intended to protect switching circuits from voltage spikes but it ALSO means you must now wire the relay coil with regard to polarity, otherwise the diode will act as a dead short. An example:
http://www.bcae1.com/images/gifs/bos...atasheet01.gif
If you hook power to 85, and the grounding switch to 86, you have a short, as the diode will conduct. I realize you stated you hooked power the other direction?

But it could be you have a bad relay? Or if a diode the diode may be backwards from "usual'.
Remove the relay, check it with an Ohm meter and see if it is dramatically lower resistance with the leads reversed on the coil on 85 and 86.
Also, fire the relay using clip leads on a battery to make sure the relay is actually OK.
I would think most any micro switch made will handle a relay...I don't know what those coils draw, but a fraction of an amp.

[Danny Cabral]

• If you don't want to concern yourself with the correct wiring polarity, just use a resistor type relay (no polarity wiring matters).
For diode relays, the relays have a schematic diagram on their side. Follow the directions below regardless of relay manufacturer:
+12V - Cathode
Ground - Anode

http://www.autoshop101.com/forms/hweb2.pdf (Diode vs. Resistor Relays - Page 12 & 13)

• It's nothing special. Although for ECU wiring, a relay with a resistor or diode (across the coil) should be used.
It's a typical five terminal automotive relay (Bosch/Tyco) that can be obtained at your local auto parts store.
The first five relays listed below, are all the same five terminal SPDT configuration, with bracket & resistor:
Tyco V23234-A1001-X043
Bosch 0 332 209 161
Hella 87420
Pico 5591PT (Relay/Wiring Kit)
Echlin/Napa AR143 (Wiring Kit)
Echlin/Napa AR204 (50 amp, diode protected - correct wiring polarity required.)

• Relay terminals (ECU ground signal scenario):
#85 - ground signal from ECU/micro switch
#86 - fused 12V power to relay coil
#30 - fused 12V power to relay contact
#87 - 12V power to electric component
#87a - not used in all applications
Terminals #30 & #87 can be reversed.
http://www.autoshop101.com/forms/hweb2.pdf (Understanding Relays)

[bruce69camaro]

It's fixed, not sure what happened, but I can tell you, I pulled all the wires off the relay, traced to where each wire went, and then reinstalled them on a new relay.
I used a toggle switch in place of the micro switch, and when I closed the switch, things worked.
So I reinstalled a new micro switch and the solenoids open when the switch is closed.
I checked to see if the first relay was OK, and it checked out fine, but just decided to put on a new relay just to be sure.
I'm going to install the first relay to see if that actually could have been the problem, even though it did check out fine.
I still think I wired it wrong for some reason, because when the arming switch was closed, you could hear the relay energizing,
but the solenoids were not opening, so I'm not sure which wires I had wrong? Thanks.

[bruce69camaro]

• Relay terminals (ECU ground signal scenario):
#85 - ground signal from ECU/micro switch
#86 - fused 12V power to relay coil
#30 - fused 12V power to relay contact
#87 - 12V power to electric component
#87a - not used in all applications
Terminals #30 & #87 can be reversed.
http://www.autoshop101.com/forms/hweb2.pdf (Understanding Relays)

We were discussing this the other day. #85 & #86, does it matter which post is used to bring power in?

[Danny Cabral]

We were discussing this the other day. #85 & #86, does it matter which post is used to bring power in?

It only matters if the relay has "diode protection". The first paragraph in post #5 explains this.