1947 P-15 Headlight Switch Fuse gets HOT

[insaneradio]

I am having a problem with my headlight switch.  My fuse holder mounted in the bottom of headlight switch get VERY hot when lights are illuminated.  When I purchased vehicle 28 years ago I had to replace the headlight switch due to the phenolic being burnt where the fuse holder mounts on bottom of switch.

 

I have unplugged each "leg" of the lighting circuit from the switch with the attempt to isolate which circuit may be drawing too much current.

 

However it is my thinking if the circuit is drawing too much current the fuse would blow---never does.  Then I thought maybe their might be a resistance connection in the fuse holder/headlight switch.  Could not find a problem with headlight switch.

 

My wiring is all original.  

 

Anyone else experience this??  If so I would greatly appreciate someone sharing the remedy!!

 

Best,

Dave

 

 

[maok]

If there is heat, there is resistance. Check for rust on contacts or wires.

[Plymouthy Adams]

check all connection as stated....do clean the grounds and ensure they are tight, a star washer will work great here..

 

you can easily prevent the heavy current from running though your headlight switch and ensure its long life by using the switch to power up a aux mounted relay...(out of sight and peace of mind)..the relay to be fed from good battery connection through an inline circuit breaker.  Connect the output of the relay to the common input of your dimmer switch, in that manner you will need but one relay as the dimmer switch will determine/control the elements appropriately.  Of course..the relay low power energizing coil is switched on when by the headlight switch, you need to ground the relay.  Cut a (Bosch style) relay and pigtail out of most any car in the junkyard for a couple bucks or buy a relay kit from a big box store.  The Bosch relay numbering and wiring can be found online very easily...IF your relay has the 5th center connection that is 87a this is a NC power point...you will not use this contact..if you find a relay with 5 and your pigtail has but the 4 slots..break off the center contact...again this allows for power to feed through 87a when relay is NOT powered up..when coil is powered 87a drops out...the circuit below is named for washer pump....substitute your word "headlight"

 

86 will be the wire you interrupt from the switch that ran to the dimmer.

87 will be the of end of the above wire running to the common input of the dimmer switch

30 is input through circuit breaker from battery, you new dedicated high current feed..

87 will be ground...

 

relays are plastic and therefore and can be used either polarity without fear of grounding out..

 

Edited July 10, 2016 by Plymouthy Adams

[JD luxury liner]

when there is a loose connection you get heat, it might be the fuse holder itself. make sure tha the fuse is tight in the holder.  i would run a relay as suggested by plymouthy.

[greg g]

You can also take the brake lights out of the circuit by repowering the switch directly from the battery side terminal of the starter solenoid through an in line fuse ,15 amp will do.

[dpollo]

 Later models and trucks with  a similar switch used a self closing circuit breaker instead of a fuse.  It mounted to the back of the switch on trucks and to the back of the gauge panel on cars. This eliminated the somewhat inadequate connections of the typical fuse holder.

 

A relay on the headlights will bypass a large amount of current and will brighten up the lights. You will have to check to see if the relay suggested by PA will operate on 6 volts or slightly less.  I had trouble with my 37 Plymouth's relay dropping open at idle, brakes on

at a stop light.

 

In practical terms a good cleanup will likely solve the problem.

[Plymouthy Adams]

if you still at 6 volt for just a extra amount the Bosch style is available in 6 volt...

 

http://www.ebay.com/itm/6-Volt-Relay-Bosch-Auto-Style-6VDC-coil-40A-30A-w-Pigtail-SPDT-6V-/201468278588?hash=item2ee871f73c:g:JvEAAOSwgQ9VzfYS&vxp=mtr

 

for less dollars you can get a solid state 3-32 volt relay...quick look found this....find what suits your need/pocket..but each has to weight their own situation and make the call to prolong the life of the switch...some may think it wrong to insert the relay...it can be done with zero cuts to the original wiring harness.

 

http://www.ebay.com/itm/New-Plastic-Metal-Solid-State-Relay-SSR-DC-DC-25A-3-32VDC-5-60VDC-TS-/172167582253?hash=item2815fcd22d:g:tgEAAOSwJMhXD7iu

Edited July 10, 2016 by Plymouthy Adams

[insaneradio]

Thank you Gentlemen for the suggestions.  I have a spare headlight switch.  I am going to clean inspect/ohm the switch prior to installation.  Once installed I will report back. 

[insaneradio]

I replace headlight switch and removed and cleaned hi/lo beam switch.  Surprisingly there is an improvement.  Still warmer than I would like.  I can place my finger on it indefinitely--however it does get warm.  I am sure we all can agree that it should not.

 

Aux relay may be my only good option.

[ptwothree]

Don't forget to clean the junction block terminals on the radiator support. And the headlight sockets.  Warm is ok...Hot....not so much.

[BobT-47P15]

One time my fuse would get hot - it was because I had accidentally switched two wires when re-hooking them to the switch. 

 

Doing the other things that have been suggested are all good ideas......as the switch also operates the dash lights, the tail and brake

lights plus the head and park lights......any lights that come on when the switch is pulled. 

[insaneradio]

One time my fuse would get hot - it was because I had accidentally switched two wires when re-hooking them to the switch. 

 

Doing the other things that have been suggested are all good ideas......as the switch also operates the dash lights, the tail and brake

lights plus the head and park lights......any lights that come on when the switch is pulled. 

Thank you for your reply.

 

Yes, when pulled to first position all lights illuminate--except headlights.  Once pulled fully out the front parking lights extinguish and headlights illuminate.

[jgreg53]

I'm having a heck of a time trying to find that 6 x 36mm fuse. 

Edited October 19, 2023 by jgreg53

[Ivan_B]

Like this? https://www.ebay.com/itm/303630583920 How many amps?  

[D35 Torpedo]

I have a trick for these situations. The factory made things to be quickly assembled. A lot of connections are a simple rivet of mechanical connection. Over time corrosion creeps into the layers and forms resistance. Build solder joints between connections on the switch. Solder the trace or tab to the rivet. Follow the current path and eliminate as many mechanical connections as possible.