Hey Del

[TrailBeast]

@67Dart273

Good morning.
The instructions for the Classic Auto Air system says to connect both power leads to switched ignition.
The system apparently draws up to 20 amps.
I want to take that load off my key switch with a relay direct to the battery and realize I probably need a continuous use relay.

I have multiple relays.
This one says 40/30 amp, but I don’t know (and can’t find) much anout it.

One problem is that the AC system power supply wires are 10 gauge, and any relay socket I have is wired with 14.
Suggestions?

The resistor is connected between terminals 85 and 86. Why is that there?

Thanks

 

[67Dart273]

That is not a resistor, that's a spike diode, to protect whatever is driving the relay, AKA EFI module. You MUST be sure you get that polarity right. Many relays have them built in, and the "internet wisdom" claims that SOME are backwards. Isn't that a bummer. The band is the cathode, and current goes from neg to positive from right to left. You do NOT want current flowing in the diode, so you must power the relay with the positive feed on the BAND end of the diode, IE the red wire pos. in your photo

(DO NOT connect polarity as shown here, these polarity markings cause the diode to conduct. You want it "turned off."

Another thing to look for is that some relays are a "trick." There are two versions I've seen and don't know what they are called. On one version, a quick glance would make you think that the relay is a double throw, AKA has one normally closed (NC) contact. But these special versions have TWO of the blades in parallel for extra current, and in fact are ONLY normally open (NO). The second version I've seen, the blades are quite large and require a different socket. Some of these are rated up into 40-50A

All these such "Bosch" style relays are continuous duty so far as I know.

This website:

Automotive Relay Guide | 12 Volt Planet

Read our guide to relays found in vehicle electrical systems. How they work, why they're used and some example applications

www.12voltplanet.co.uk

Pictures the difference between a SPDT and one with bridged blades for more current, SPST only. They are calling the SPDT a "changeover" and the SPST a "doubled output

 

[AJ/FormS]

I have used Mopar starter relays to good effect. They don't look hi-tech, but they get the job done ...... for decades.

 

[TrailBeast]

That is not a resistor, that's a spike diode, to protect whatever is driving the relay, AKA EFI module. You MUST be sure you get that polarity right. Many relays have them built in, and the "internet wisdom" claims that SOME are backwards. Isn't that a bummer. The band is the cathode, and current goes from neg to positive from right to left. You do NOT want current flowing in the diode, so you must power the relay with the positive feed on the BAND end of the diode, IE the red wire pos. in your photo

(DO NOT connect polarity as shown here, these polarity markings cause the diode to conduct. You want it "turned off."

View attachment 1716272042
Another thing to look for is that some relays are a "trick." There are two versions I've seen and don't know what they are called. On one version, a quick glance would make you think that the relay is a double throw, AKA has one normally closed (NC) contact. But these special versions have TWO of the blades in parallel for extra current, and in fact are ONLY normally open (NO). The second version I've seen, the blades are quite large and require a different socket. Some of these are rated up into 40-50A

All these such "Bosch" style relays are continuous duty so far as I know.

This website:

http://[URL]https://www.12voltplanet.co.uk/relay-guide.html

[/URL]

Pictures the difference between a SPDT and one with bridged blades for more current, SPST only. They are calling the SPDT a "changeover" and the SPST a "doubled output

View attachment 1716272043

That clears that up.
Thank you for the effort you put into this.
I appreciate it.