Horn Relay or Switch

[Dennis Detweiler]

I rewired my 39 Plymouth from scratch by making a schematic first. I don't understand the 4 prong switch on your schematic? My "relay" is 4 prong, but a modern relay. #86 to horn button, #87 to horn, #85 to fuse panel, #30 to B on voltage regulator which also goes to the battery and incorporates a 20A fuse between the voltage regulator (B) and the relay terminal (30). My horn works without the ignition turned on, as does all cars.

I upgraded my whole re-wire project using two fuse panels (one is hot and the other works only with the ignition), utilizing 11 fuses (separate circuits). I also used 8, 10, 12 and 14 guage wires,  depending on the load required. I also used two separate relays for the headlights  (high beam and low beam).  The original 39 schematic only had a fuse on the light switch and a fuse on the horn.   

[Tom Skinner]

Dennis,

I am also looking into a 20 AMP Fuse to the B on the Voltage Regulator.

Tom

[Dodgeb4ya]

Is your horn relay wired up exactly as shown.... Horn = heavy wire to horns

                                                                                    GRD  = connects to horn button

                                                                                    BAT  =  connects to 6 volt always hot feed off  "B" of voltage regulator terminal or starter cable

                                                                                    IGN  =  connects to ignition SW six volt key on feed at trans relay "BAT" terminal or any key on feed

Do you have a new Yand Z or Rhode island wire harness and are all the wires to the relay green? 

Is your four terminal relay a NOS Autolite HRL 4101....is it new old stock? It might not work especially if hooked up wrong. Terminal markings are on the mounting ears.

Edited January 9, 2019 by Dodgeb4ya

[Plymouthy Adams]

at this point, it is quite evident you need to prove a few things, first the VOM to verify the marked connections on the relay are what they are report, the fact that the horn will work direct connection and finally that your wires coming to and from the relay ACTUALLY go where they are supposed to be going.....all this is just a couple simple minutes with the VOM and will remove ALL guessing of the wiring, relay marking and operation and the horn itself.  

[Dodgeb4ya]

Not much to your horn relay and testing it like PA states....

[Tom Skinner]

Dodgeb4ya,

Thank you for the schematic. I have H and IGN right, I will look into the B and S later after work today.

Thank you. I think I need to have a 20 AMP Fuse to B also then it will be sorted out.

Thanks again!

Tom

[Merle Coggins]

Do you have a volt meter to confirm that you have voltage at the IGN connection with the key on? You can also check that the wire to your horn button is truly grounding when pressed. These are a couple of the tests Plymouthy is referring to. VOM = Volt/Ohm Meter. (A.K.A. Multimeter)

[Dodgeb4ya]

No fuses are really needed if wired correctly IMO.

[MarkB2PW]

Tom

I had the same problem a while back and I'm just now getting around to fixing it.  Forgive me for being cheap, but, is there another way to wire the horn without spending ANOTHER $100 for the relay?  Will  a modern relay at 1/4 of the price work? 

[Plymouthy Adams]

the question at hand is valid but often the rating of the voltage is the issue...modern 12 volt relays are wound for proper clamping action as the result of the magnetic force induced by the coil with 12 volts applied...while it possible that the 6 volts will energize a 12 volt coil, the clamping force may not be enough to prevent chatter or high resistance of the load contacts when used.  Now, if you have already converted your car to 12 volts, you are golden and the low cost BOSCH style relay is an excellent choice.  Many here have 6 volt issues, this is the higher cost as they also want to appear completely stock.  If stock is not an issue but 6 volt is, then are modern solid state relays that will operated 3-32 volts input for the current rating you need are available all day long at a give away cost.

[Dennis Detweiler]

I bought the modern 4 post electronic 6v relays on ebay.

[Dennis Detweiler]

I'd rather have too many fuses than not enough. I've seen too many cars short out and wires burn. Sometimes the whole car. A fuse block with everything on separate fuses is easier to narrow down a specific electrical problem if a fuse blows. It also keeps components like a radio from being completely destroyed.

Mark, the photo of your old wires is why I gutted mine and installed all new wiring. Fire trap. After I purchased my 39, drove it home and had a good look at the wiring, I was lucky it didn't burst into flames on the way home. I also soldered all of my terminals onto the new wires. New wires, individual fuses, no crimps, no worries. all lights are bright, horn is loud, radio works good.

[Tom Skinner]

The 6 Volt 3 Prog Relay came today in the Mail. The  H. B. S. Relay I had on Order through Ebay. An Echlin. I hooked it up again and prestodigitorium my horn works fine again.

I don't know how, I just know it works. As the say in Japan in the House of Delight - A Velly velly happy Ending. L.O.L.

Echlin Parts are U.S. Made

Tom

Edited January 10, 2019 by Tom Skinner
Spelling

[Dennis Detweiler]

Ah-so

[BobT-47P15]

 

 

Tom....here is a wiring diagram for a 46-48 Plymouth P15........showing everything including the horn circuit.  Your horn relay appears to be mounted on the inner fender, whereas mine is attached to the horn mounting bracket.  They should both operate in the same manner.  I can't understand why two relays would be needed if all wiring is correct,   

 

 

Edited January 18, 2019 by BobT-47P15

[Dodgeb4ya]

Two relays are not needed  if the cars horns, horn ring, relay and wiring are all in working order as designed.

I've never needed two on any of my 1946-48 MoPars.

The horns work very well with one relay and I'm saving wear and tear on the generator too.

[Eric]

On 1/9/2019 at 12:16 PM, Plymouthy Adams said:

the question at hand is valid but often the rating of the voltage is the issue...modern 12 volt relays are wound for proper clamping action as the result of the magnetic force induced by the coil with 12 volts applied...while it possible that the 6 volts will energize a 12 volt coil, the clamping force may not be enough to prevent chatter or high resistance of the load contacts when used.  Now, if you have already converted your car to 12 volts, you are golden and the low cost BOSCH style relay is an excellent choice.  Many here have 6 volt issues, this is the higher cost as they also want to appear completely stock.  If stock is not an issue but 6 volt is, then are modern solid state relays that will operated 3-32 volts input for the current rating you need are available all day long at a give away cost.

 

[Eric]

I have a 52 Cranbrook ... can you tell me which modern solid state relays that will operated 3-32 volts input will work on my car ...had a small fire from original horn relay and want to change it ..the wire going from the ignition switch started on fire . why ? 

[Eric]

I have a 52 Cranbrook ... can you tell me which modern solid state relays that will operated 3-32 volts input will work on my car ...had a small fire from original horn relay and want to change it ..the wire going from the ignition switch started on fire . why ? Want to keep original 6 volt but dont want to pay 120 for a old new part horn relay ? need help here . 

 

[Sniper]

the wire caught fire because somewhere in that circuit you have a short.  Fix that first.

 

Solid state relays work differently that a mechanical relay, results are the same, function is different..  If the actuation voltage range is 3-32V then it will work when 6V is applied.  You will need to make sure that it is rated for the current draw through it though.

 

You will also need to sort out how to wire it as the original horn relay is also a power distribution point.

[Plymouthy Adams]

shopping about is still the game you play based on initial cost plus shipping.  You will need to buy your relay for secondary contacts (load)....what and where you buy is your call, search for solid state relay dc-dc....you will need to know your load amperage....or if unsure buy based on an overkill guess.   Typically online these are available yet at about the same cost you will pay for a new Bosch style mechanical relay at the big box store...

[greg g]

Bosche 6v relays have some that will do 30 amps. Horns probably pull 7 or8 amps each so a 20 Amp should do the job.  Be carefull you get a momentary  relay, not a latching one.  The latching style stay energized until they get another signal.  You don't want this for horns. You don't want a self grounded g type either.

 

When wiring the power side of the relay, ie: high load from battery to relay to horns, 10 gauge wire is your friend. You can do relay switch side with 12 gauge.  So three terminals would be 10 gauge, and the wire to the grounding wire at the steering box can be 12.

[Eric]

12 hours ago, Sniper said:

the wire caught fire because somewhere in that circuit you have a short.  Fix that first.

 

Solid state relays work differently that a mechanical relay, results are the same, function is different..  If the actuation voltage range is 3-32V then it will work when 6V is applied.  You will need to make sure that it is rated for the current draw through it though.

 

You will also need to sort out how to wire it as the original horn relay is also a power distribution point.

 

[Eric]

https://www.rockauto.com/en/moreinfo.php?pk=319745&jsn=3 will this work with only three connections ?

 

 

[Sniper]

Most likely, you;ll have to look at the drawing in you manual and compare how the original is hooked up then look at the drawing for the horn relay to sort out what goes where.