Relay for HID lights

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=87693
Printed Date: May 13, 2025 at 1:51 PM

Topic: Relay for HID lights

Posted By: tsayta7722
Subject: Relay for HID lights
Date Posted: December 23, 2006 at 4:37 PM

Can anyone help this rookie?

Just bought an aftermarket HID headlight system for 2005 Mustang. Had to install a relay to take power direct from battery rather than thru stock harness. When lights turned on with engine not running, works great. BUT start the engine and the relay buzzes like crazy! I see that perhaps I should install a capacitor (2200uf or so) across terminals 85 and 86, observe polarity AND I should add a small diode (1N4001) in series on the terminal 85 lead (band towards the relay).

Do I need both? I found a diagram for diodes but nothing for capacitor. Can anyone show me a simple diagram that a non-expert can read so as to put this together? It is a Bosch relay. This diode and capacitor, can I get it at Radio Shack?

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Replies:

Posted By: KarTuneMan
Date Posted: December 24, 2006 at 11:53 AM

you need a relay with nothing on it....NO diode. NO cap. Also...you want 1 relay for each light!

I am assuming you have the relay wired correctly.....? Good ground?

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Posted By: tsayta7722
Date Posted: December 24, 2006 at 1:39 PM

Relay has a good ground. Direct to car frame. Seems that when car is running, either the current passing thru the coil of the relay is intermitted or it is pulsating or something. Only happens when car is running. Went to Radio Shack (The Source by Circuit City) yesterday. Purchased a rectifier diode 6amp and a 2200uf capacitor. Whired the capacitor across 85 and 86, then wired the diode in series before 85 band toward relay. Tried it out and...

BUZZING IS GONE! Works flawlessly. I guess the current must have been pulsating or something and the diode prevents this by allowing one way flow only?

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Posted By: tsayta7722
Date Posted: December 28, 2006 at 8:54 PM

Sent: December 27, 2006 at 6:22 PM

hey, i just bought an hid kit and also require a relay. could you please tell me how you set it up, what things where needed etc.

i am not an expert so lamens terms would be awesome. if possible pics would be greatly apreciated.

please email me at angeleye104@hotmail.com when u get a chance, thanks alot

Lucky for you, I just went thru all this so here is the deal...

-I have a 2005 Mustang

-Bought a Chinese knock-off HID system. Nothing wrong with that.

-Installed on stock headlight harness as per instructions, but lights flickering badly. If this happens to you, disconnect immediately cuz this is bad for zee ballasts.

-Turns out the stock wiring harness for any car uses way too skinny wires, so you MUST have a better power source. Sounds scary, but it is WAY EASY.

-They call it a relay system. All that means is that you connect the headlight harness to a switch (called a relay) that coonects your battery to the HID ballast and only turns on when you say so.

HERE'S THE DEAL:

-go to your local auto parts source and ask for a 12 volt SPDT Bosch relay.

-get some nice 12 guage wire (also known as thick wire).

-connect the RED wire from your headlight socket to terminal 85. Not sure whats terminal 85? The darned Bosch thingy actually has a lable! Not sure which is the red wire from the headlight socket? Its the one that gives power WHEN you switch on zee lights from inside.

-connect a wire from ground anywhere on the car frame to terminal 86 on the relay.

-connect a dedicated wire from RED battery post to terminal 87 on the relay. Do a 30amp inline fuse.

-connect a wire from the other post on the Bosch relay to your HID inbound line. Yes, I know, there is one more unused post right smack in the middle of the Bosch relay. Ignore it, it is only use by communists (just kidding, it is for if you want your lights to stay ON all the time and you use the switch to turn them off).

OKEY DOKEY:

-do not start thye car. Turn on your lights. When you throw your headlight switch, terminal 85 and 86 get continuity and close. This causes terminal 87 to pass power to the HID unit directly and WHAMO, you got light.

-now start the car. If the relay starts to buzz like a mad grasshopper, email me and I will send you thye $3 fix.

Best of luck ol' mate from a crazy Canadian freezing his ass off waitin' fer summer!

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Posted By: egomez2112
Date Posted: January 07, 2007 at 12:21 AM

Hi,

I have a 2003 GMC Envoy. My problem is a bit different.

Bought a cheap china made hid conversion kit. Plugged it into the vehicle harness (one ballast per side) and had flickering problem. I tried using a relay to get power from the battery. Worked ok when I turned the key and started engine. Lights worked fine. However, when I used the remote to unlock the doors the relay buzzed like crazy and the lights flickered. I tried checking the voltage on the vehicle wiring harness and could not detect anything unusual like reverse polarity or significant voltage shift.

Can you send me a diagram on how you stopped your relay from buzzing? Also, do you know what caused the buzzing?

Thank you.

Posted By: tsayta7722
Date Posted: January 07, 2007 at 1:59 PM

-from the headlight socket you ran a wire to terminal 86 or 87 on the relay. This is just the extension of the headlight switch that tells the relay when to power on.

-the relay buzzes because power to the relay is somehow pulsating back and forth. The solution is to have a one-way valve installed so that power goes only towards the relay. This is the purpose of the diode.

-install it between the headlight socket and the relay with the band towards the relay.

-i also installed a capacitor between term 86-87 in case to absorb any large voltage spikes

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Posted By: egomez2112
Date Posted: January 26, 2007 at 6:11 PM

I tried connecting the diode between the positive lead of the factory bulb socket and terminal 86 of the relay and still cannot stop the buzzing. I don't know what is causing this. I tried several diodes and do not think they are all defective.

Can it be a ground loop problem?

Any suggestions/solutions are appreciated.

Thanks.

Posted By: tsayta7722
Date Posted: January 26, 2007 at 9:39 PM

You got the diode in wrong spot. It must go between the headlight switch and the relay, band towards relay. In other words, when you turn on the headlight switch, you are asking the relay to close a circuit and supply power from the battery direct to the HID ballast. Sometimes what happens is the 'signal' or power from the headlight switch to the relay necomes intermittent or alternates. When it alternates, it cause the swith in the relay to open and close rapidly (one millisecond open, one millisecond closed). This is the buzzing you hear. The diode provides a one way valve telling the circuit to stay open, it ignores the alternating current. So find the wire that you ran from the socket where your stock headlight bulb used to plug into, trace it back to your relay. Cut this line and install diode here (band towards relay)

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Posted By: tsayta7722
Date Posted: January 26, 2007 at 9:41 PM

also, check you don't have connections at the relay reversed. If your wire from the headlight socket goes to the post on the relay where the direct power from the battery is supposed to go, you are set up backwards.

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