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Discussion Starter · #1 ·
I am just installing new headlamps in my 73 vette. I have put semi sealed beams with 55/65w globes in the hi/low lamps and have put 100w sealed beams in the high beams.
My question is - do I need a separate relay for each globe, or can I just one one relay for the high beams and one for the low beams.

Sorry if this has been asked before.

Jeremy
 

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jjl said:
I am just installing new headlamps in my 73 vette. I have put semi sealed beams with 55/65w globes in the hi/low lamps and have put 100w sealed beams in the high beams.
My question is - do I need a separate relay for each globe, or can I just one one relay for the high beams and one for the low beams.

Sorry if this has been asked before.

Jeremy
1 for high and 1 for low as long as the relay is rated high enough to hadle the load.
 

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30 amp relays will do fine, just use #10 wire from the power source on one side of the normally open relay contacts and #10 wire from the other side of the normally open contacts to the lamps.

FWIW, use a quality #10 wire. I have found the wire typically available in my local auto parts stores is very cheap quality with insulation that melts very easily when soldering on connectors. The quality wire from places like Painless and American Auto Wire does not do this. The quality wire will be GXL rated which means it's a high heat resistant insulation.

Vince
 

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Doc here, :pimp:

To Calculate for Contact ratings, apply a little OHM's law:

I=P/E..

OR , in your case, 65 watts / 14.4 Volts (operating speed voltage) = 4.51 Amps Draw Per Lamp...

30 Amp Contact ratings should be more than enough to handle the Draw.

You Should use TWO relays, One for High Beam, One for Low Beam to eliminate the draw OFF the switch gear and on to the RELAY contacts. (more power to the lamps, and longer Switchgear life)

The 10 gauge upgrade is , (RELAY CONTACTS to Battery and lamps) as was said , needed to help deliver that load to the lamp circuits without heat or current losses, the RELAY COIL wires (the ones coming from the switch in the car to the engine bay) May remain 12 or 14 Gauge stock wire ( They Will now only be handling about an amp..as opposed to full lamp current.)

MAKE sure you Find a GOOD bonded ground for the relay coil grounds on the Vette..you could end up with fluttering Headlamps when you hit bumps if you don't...

Doc :pimp:
 

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Discussion Starter · #6 ·
Thank you everyone for your adice re the relays.
I have two relays (30amp) and will set them up as described.
I will put a fuse on each circuit as well just to be on the safe side.
 

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jjl said:
Thank you everyone for your adice re the relays.
I have two relays (30amp) and will set them up as described.
I will put a fuse on each circuit as well just to be on the safe side.
A fuse for the dims and a fuse for the brights would be advisable.

Vince
 

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Mrwood said:
Why cant you just use fuses and do away with the relays. Are the relays something we have to use.

Doc here, :pimp:

A relay is a remote switch..

It operates a set of high current capable contacts, from a low current control point..

A relay coil generally pulls about an amp..this means to energize the relay , I don't have to run high current through a dash switch, or hi/low switch, the switch gear will last forever, AND I have no heat loss (wasted energy, doing no useful work) to the lighting system from the switch.

The Contacts of the relay are doing the high current work, 20, 30, 40 and sometimes more amps, and with the proper size wire, will deliver the maximum current from the source (Battery direct) to the Load (The lighting system)

The result is switchgear that lasts forever, No heat loss, no potential overloads and fire, and the lamps shine about double the lumen's over stock.

Doc :pimp:
 

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Mrwood said:
Ok i understand. Guess i better do some rewiring on my light system. Thanks for the reply.
Doc here, :pimp:

It's not mandatory to do an a sock car, But a Very nice addition, makes the lights much brighter, and switches last forever..IT IS if you add High Current headlamps..the stock system usually won't support the draw..

As important as the relay , is running 10 gauge wire from the relay center wiper to the headlamps, AND 10 gauge wire from the fuse link or maxi and battery, to the center wiper of the relay..The coil wires can remain stock from the switches (usually 12 or 14 gauge) as they will now only be controlling a relay coil , about an amp.



  • Mechanically install your Relays out here in a dry place away from fuel, hydraulic, lines and rotating parts, securely mount them.

  • Cut and remove the wires going to the head lamps , replace them with 10 gauge wire..

  • The 2 wires Coming from the switch, (the other side of the headlight wires you cut) , determine which is low beam and which is high beam, each of these wires will go to terminal # 85 (RELAY COILS) of each relay. (one high, one low beam.)
  • RELAY COIL #86 = properly bonded , hard body ground. use star washers and burnish paint.
  • RELAY CONTACT #87 NORMALLY OPEN = (both relays) 10 gauge wire goes to a proper fuse link, then to the battery OR starter solenoid battery terminal.
  • RELAY CONTACT # 30 CENTER WIPER= (Both Relays) goes to the headlamps, One to high beam terminal, the other to the low beam terminals.
  • RELAY CONTACT # 87A NORMALLY CLOSED is not used for this application.

You'll be happy you did install them though..great for night driving.

Doc :pimp:
 
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