*How To Install A Relay*

[Zippi]

First let me say I know nothing about the electrical portion of a car. I have installed a new set of bucket seats in my 49 and the drivers seat is electric. I have put power to it and it all works fine. I'm told it needs to be connected to a 20 amp relay. I will have one + wire and one - wire coming from my seat. Can someone tell me where these two wires will connect to the relay and where the power will connect. I've looked at wiring diagrams its Greek to me.

[Andy4639]

Originally Posted by Zippi

First let me say I know nothing about the electrical portion of a car. I have installed a new set of bucket seats in my 49 and the drivers seat is electric. I have put power to it and it all works fine. I'm told it needs to be connected to a 20 amp relay. I will have one + wire and one - wire coming from my seat. Can someone tell me where these two wires will connect to the relay and where the power will connect. I've looked at wiring diagrams its Greek to me.

Ok here you go.
Your relay should be marked with the same numbers as my drawing.

1-You will need a wire straight off the fuse panel are battery that has a good 12 volts on it all the time to plug in to the #30 terminal of the relay with a 25-30 amp fuse in line.
2- Then the + wire you have from the seat will go to terminal #87.
3- The - wire from the seat can go straight to the frame.
4- The relay terminal #85 will need a ground as well. You will need one relay for each seat.

[lutronjim]

Why is a relay needed? Why not just a fuse?

[Richard]

If installed properly the relay will allow power to flow directly from the power source to the device. The switch just activates the relay. In your case ignition turned on will power relay (86). Power to relay from battery (30) should be direct as possible to battery meaning not through switches or other devices. The information provided by the previous post is good. While I disagree a standard 30 amp Bosch relay should be fine for both seats provided adequate wire size is used.

[The Rocknrod]

Originally Posted by lutronjim

Why is a relay needed? Why not just a fuse?

Relays are used in circuits to reduce the current that flows through the primary control switch (like a headlight switch). So your using relatively low current to control the relay (for the headlights), instead of running high amps thru the light switch.
A smaller switch or sensor can be used to turn a much higher capacity relay on and off.

[Zippi]

Thanks for the info guys. Only the drivers seat is power so do I still need a 25-30 amp inline fuse? What amp relay do I need? Same size as the inline fuse?

[Zippi]

I have a second smaller fuse block with an open spot. I'm not sure what the amp rating is on this block. Can I run a wire from this fuse block to #30 terminal?

[Andy4639]

The relay should be a 30/40 amp and the fuse should be at least 30 amp.
It's like your head lights. You want as much power to get to the seat motor as possible.

No you don't have to put 2 relays in for both seats but if some point 2 people hit the seat switches at the same time then you will know why I suggested 2 relays.

[Zippi]

Originally Posted by Andy4639

The relay should be a 30/40 amp and the fuse should be at least 30 amp.
It's like your head lights. You want as much power to get to the seat motor as possible.

No you don't have to put 2 relays in for both seats but if some point 2 people hit the seat switches at the same time then you will know why I suggested 2 relays.

Thanks for the help.

[Andy4639]

Originally Posted by Zippi

Thanks for the help.

Your welcome sir!

[lutronjim]

If The Rocknrod is answering my question of why a relay, all the cars that I have had didn't have any switch to power the seats - not even ignition. They were, I guess, fused directly from battery. You could open door and move seat.

If the little woman had the seat under the steering wheel and you wanted to get in, you might have trouble reaching the switch or ignition.

[Andy4639]

It had to be switched from some place are the seat wouldn't move.
You said your self the switch had to be pushed once you open the door!

[G8rN@te61]

so installed a relay for my HEI same as this diagram and now when I turn ignition off it sometimes doesn't turn the relay off. What would cause this? bad relay? Bad ignition switch? I am wondering if I should just ditch the relay and run a "ignition on" wire from the fuse block all the way to the HEI?

[Andy4639]

Originally Posted by G8rN@te61

so installed a relay for my HEI same as this diagram and now when I turn ignition off it sometimes doesn't turn the relay off. What would cause this? bad relay? Bad ignition switch? I am wondering if I should just ditch the relay and run a "ignition on" wire from the fuse block all the way to the HEI?

I would say you either have the relay wired wrong are it's a bad relay.
Myself, I don't use a relay in the ignition wire going to the HEI.

[toolboxchev]

Well, I have time on my hands so I thought to throw this out there. Are not some of the Bosch Relays a 5 pin or connection?

So I see again there are a couple types, even with 5 pin, sometimes used all 5 and sometimes not.

https://www.davebarton.com/pdf/RelayGuide.pdf

[Andy4639]

5 Pin Relay
5 pin relays provide 2 pins (85 & 86) to control the coil and 3 pins (30, 87 & 87A) which switch power between two circuits. They have both normally open and normally closed connection pins. When the coil is activated, power will be switched from the normally closed pin to the normally open pin.

In other words say you have a 2 speed fan. You hook low speed to 87A so that when ever the car or truck is running the low speed fan is also. Then when you turn the AC on it triggers the relay to turn the power off of 87a and go to 87 so the high speed fan will run to keep the AC cool.