6 volt relays
- Thread starter 31chevy
- Start date
37 Coupe
Well-known member
I was told NAPA has them but I had no luck or help in finding them. I found a good one on Ebay if you want a good old mechanical type relay made in the USA. Ebay item # 350247109257,this was actually one made for auto industry by RBM probably right here in my hometown in Ohio. I am using it to relay power to a four fuse panel for fuel pump switch,heater and turn signal switch and radio. If you search Ebay for 6 volt relay you get quite a few choices and a couple new ones I imagine solid state made in China ,Mexico Portugal etc. I was told a couple weeks ago on Fordbarn that Bosch makes a good one but never found a 6 volt one. Fordbarners are great help, Henry/Kokomo took the time to send me a diagram of where everything should go and how to hook up.
Henry/Kokomo
Well-known member
Depending on your needs, you might try NAPA. They may be able to get 6 volt, early '50s horn and/or headlight relays that look "period correct". For something smaller and less obtrusive, I'd check Radio Shack. Your degree of success may depend on the experience of the people who wait on you in the stores. Maybe an on-line search? FWIW
Old Henry
Well-known member
Here's a 12 volt one that you could run down to Radio Shack and pick up for under $5.00. It would probably work with 6 volt since it doesn't take much juice to activate the electromagnet for a relay. The secondary (switched) side of the relay doesn't care about voltage since it's just a switch. If it doesn't work, just take it back. http://www.radioshack.com/product/index.jsp?productId=3020762
Last edited:
Old Henry
Well-known member
A horn relay wouldn't work because the primary circuit is energized by grounding only. It can't be powered by an independent power source as relays typically are. It shares it's power source with the secondary circuit.
Last edited:
Mike51Merc
Well-known member
What is the relay for? Besides just voltage, there are different kinds of relays. Some are triggered by ground, some are for momentary contact, some for continous duty.
A headlight relay, a horn relay, and an overdrive relay are three completely different animals.
A headlight relay, a horn relay, and an overdrive relay are three completely different animals.
Joe KCMO
Senior Member
I am interested in your statement. With a positive ground horn relay you ground the circuit and the relay closes , the power comes directly from the negative power source to what ever. So what if it shares the negative. If the relay operates a horn why would not operate something else. Not arguing, trying to learn.
jan bogert
Senior Member
i installed a 6 volt electric fan on my av8 and mounted a model a cut out relay that was on the generator to my firewall.one wire to the fan and the other to the ignition switch. works fine. i have one on ebay right now, that has the ford script on it . my car mine trying to keep old school, and that is old school JAN. i also used a inline fuse from fan to relay.
Mike51Merc
Well-known member
Bench test a horn relay for continuous use and you'll find it gets too hot to touch within a minute.
Old Henry
Well-known member
Thanks for your question.
When I first saw the inquiry about a 6 volt relay I had the same thought, "Why not a horn relay?" and was about to post such until I thought about it further.
In the picture and diagram below you'll note that the horn relay has just three connections. One (marked B for battery) is to apply current to the relay which is attached to both the primary and secondary circuits inside. A second contact (marked S for switch) attaches to the wire that goes through the horn button to ground. The third connection (marked H for horn) goes to the horn. When the primary circuit is grounded it completes the circuit that energize the electromagnet and closes the secondary circuit which then powers the horn. That's fine if that's all you want to do - close a switch to a larger load by closing a switch to ground. That's exactly the same as the starter solenoid. But, you can't switch on a load through that kind of relay by turning on the ignition switch. That is because such function requires two seperate isolated circuits through the relay as illustrated and explained below.
The usual use for a relay is to use a low current such as from the ignition switch to close the relay and power a higher current need such as a fuel pump, heater fan, stereo, etc. As you can see in the pictures and schematic below, for it to work like that you need 4 connections. One (85) that takes low current from the primary source such as the ignition switch, a second one (86) to ground for that primary circuit, a third (30) that takes the higher current from the battery, and the fourth (87) that sends the higher current to its higher need.
The only way a horn relay could be made to work like that would be by hooking it up "backwards." You would use the primary connection that would normally come from the battery as a ground. Then run your primary source from the ignition switch to the ground connection on the relay (that would normally go to the horn button.) The accessory to be switched by the secondary circuit would have to have the current go directly to it first then through a ground wire to the horn connection of the relay so that when it was energized it would be grounded and work. It could work like that but you'd have to insulate the accessory from ground and complete the ground circuit through the relay.
Better to just get a standard 4 connection relay for switching high current with low current such as the one I posted in #5 also shown above with the same schematic on the side of that relay as is shown above or a headlight relay that works exactly as described above.
Last edited:
37 Coupe
Well-known member
What about the relay I mentioned in my first post. It is a headlamp relay with a 20 amp fuse and 4 terminals,battery,switch ,ground and power out? Old school Made in the USA.Thanks for your question.
When I first saw the inquiry about a 6 volt relay I had the same thought, "Why not a horn relay?" and was about to post such until I thought about it further.
In the picture and diagram below you'll note that the horn relay has just three connections. One (marked B for battery) is to apply current to the relay which is attached to both the primary and secondary circuits inside. A second contact (marked S for switch) attaches to the wire that goes through the horn button to ground. The third connection (marked H for horn) goes to the horn. When the primary circuit is grounded it completes the circuit that energize the electromagnet and closes the secondary circuit which then powers the horn.
The usual use for a relay is to use a low current such as from the ignition switch to close the relay and power a higher current need such as a fuel pump, heater fan, stereo, etc. As you can see in the pictures and schematic below, for it to work like that you need 4 connections. One (85) that takes low current from the primary source such as the ignition switch, a second one (86) to ground for that primary circuit, a third (30) that takes the higher current from the battery, and the fourth (87) that sends the higher current to its higher need.
A horn relay could be made to work by hooking it up "backwards." You would use the primary connection that would normally come from the battery as a ground. Then run your primary source from the ignition switch to the ground connection on the relay (that would normally go to the horn button.) The accessory to be switched by the secondary circuit would have to have the current go directly to it first then through a ground wire to the horn connection of the relay so that when it was energized it would be grounded and work. It could work like that but you'd have to insulate the accessory from ground and complete the ground circuit through the relay.
Better to just get a standard 4 connection relay for switching high current with low current such as the one I posted in #5 also shown above with the same schematic on the side of that relay as is shown above.
Joe KCMO
Senior Member
Old Henry,
I understand how a relay works. My question is that with a + ground relay both the primary circuit and secondary circuit can be fed from the same source. Then when you ground the primary circuit with a + ground the switch closes and supplies the negative full power to the load. Meanwhile the full load would not flow thru the horn grounding wire, although still connected. I understand the relays get hot, that is because a lot of amps is flowing thru it. Not a sign of being able to last. Do you ever see how hot the ignition resistor gets and it is on all the time.
My question would be what amp rating is given to horn relays.
I understand how a relay works. My question is that with a + ground relay both the primary circuit and secondary circuit can be fed from the same source. Then when you ground the primary circuit with a + ground the switch closes and supplies the negative full power to the load. Meanwhile the full load would not flow thru the horn grounding wire, although still connected. I understand the relays get hot, that is because a lot of amps is flowing thru it. Not a sign of being able to last. Do you ever see how hot the ignition resistor gets and it is on all the time.
My question would be what amp rating is given to horn relays.
Last edited:
Old Henry
Well-known member
What about the relay I mentioned in my first post. It is a headlamp relay with a 20 amp fuse and 4 terminals,battery,switch ,ground and power out? Old school Made in the USA.
That would work. That's the same relay I was describing. My "treatise" was mostly to explain the difference between that kind of relay and the horn relay and how they each function differently and do different things for different purposes.
Last edited:
Old Henry
Well-known member
The horn relay works great for what it is designed for. It is exactly the same kind of relay as the starter solenoid - power coming into the relay from a constant source then switched to the load through the secondary internal switch by grounding the primary circuit. If that's what you want that works great. That is the very simplest of relays and is used for the horn and starter so that the huge load to the horn and starter doesn't all have to pass through the horn switch and starter switch. A single small wire can be run from the relay to a ground switch to activate the relay without doubling the wires to and from the switch. Such a simple relay might also be used for a fuel pump that is powered by the secondary circuit of such a relay with the ground wire of the primary going to a grounded toggle or intermittent normally open switch under the dash. But, power to the fuel pump could not be controled by the ignition switch with that kind of relay.
The kinds of relays most want in their cars is the one that is activated by turning on the ignition which then activates the relay to connect the constant source of power from the battery to the load without putting the full load through the ignition switch. To isolate the primary circuit from the secondary circuit in that way requires the 4 connections described.
BTW, the polarity of the current going through a relay doesn't make any difference how it works. Any current will magnetize the coil and close the secondary circuit regardless of which direction it's flowing through it. So, it doesn't matter whether it's positive ground or negative ground.
Last edited:
Old Henry
Well-known member
I found a rating for Model A horns as 4.5 amps and Model T horns as 5 amps. I haven't yet found the amperage for the newer 6 volt horns but I would speculate that it is about the same. That should give you some idea of how many amps at 6 volts the horn relays can carry. If I find out more I'll add it.
KiWinUS
Well-known member
I did a google seach & found NOS Bosch 6v relays used on volkswagens when I needed some for my RHD 36 . I used them on the front turn signals using amber fog lights , I was sure the fog lights pulled too many amps to run thru flasher unit & turn signel switch. It works great !
Cheers
Tony
Cheers
Tony
Wltr_Mitty
Junior Member
Here's another option: The Bosch relays were a little too pricey for me so a google search turned up these identical SPDT take-offs for ~$3.50 ea. They look and mount just like the Bosch units.
Tyco Electronics 0-1432873-1. They're 6v, 40 amp low resistance relays and you can get them here:
http://www.newark.com/jsp/displayProduct.jsp?sku=21M4888&CMP=KNC-G-SKU-TECONNECTIVITY
I use two of them on the grey coupe... one for the electric fuel pump and one for a universal 6v wiper that I sometimes swap out for the vacuum unit on cross country trips (one advantage of not having a headliner installed)... Both are wired with switches off of the ignition circuit so everything shuts down with the key. I've been using them for almost three years now w/ no trouble.
Tyco Electronics 0-1432873-1. They're 6v, 40 amp low resistance relays and you can get them here:
http://www.newark.com/jsp/displayProduct.jsp?sku=21M4888&CMP=KNC-G-SKU-TECONNECTIVITY
I use two of them on the grey coupe... one for the electric fuel pump and one for a universal 6v wiper that I sometimes swap out for the vacuum unit on cross country trips (one advantage of not having a headliner installed)... Both are wired with switches off of the ignition circuit so everything shuts down with the key. I've been using them for almost three years now w/ no trouble.