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fog light relay--highbeams not turning off

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Old 11-28-2003, 03:13 PM   #1
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fog light relay--highbeams not turning off

Hello all,

I upgraded my headlight wiring as indicated in the tech article. The strange thing is when I connect my stock wires to the upgraded harness I get some voltage on the highbeam wire with the high beams off. With no lights hooked up to the highbeam wire, the voltage is around 7.5 or so. With the highbeam wire connected to the new harness, it's around 5V. With the stock wiring connected to the headlights, the voltage is around 148mV. I traced the problem to the fog light relay. Now, the problem isn't in the relay itself, it may just be the way it is connected. There is no real ground running to the relay, as far as I can see. When the highbeams go on, the wire that carries the low voltage switches to high, switching the relay on, turning off the fog lights.

Does anyone else have this problem? Should I wire a resistor in where the stock headlight wires run to the new harness?

Thanks,
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Old 11-29-2003, 11:33 PM   #2
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the foglights are supposed to shut off when the high beam circuit is activated. is that what is happening? your post is a little hard to follow. if thats whats going on its normal.
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Old 11-30-2003, 11:51 AM   #3
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Hi, thanks for responding.

No, I have no problem with that functionality. The problem I am having is that the green wire running from the relay is supposed to be low, and the relay turns off when it goes high. Well, there's voltage on the line, it's not ground, it's around 5-7V. When it goes high, the high voltage is fine.

I traced that a bit, and the high-beam headlights are supposed to act as a pull-down resistor. However, since I've upgraded my harness, as per the tech-article, there seems to no longer be a pull-down. I'm not sure if the relay on the new harness for the high-beam wiring should function as a pull-down or not. I was wondering if this is normal, and if anyone is experiencing this.

The problem I am having is this. I turn on the headlights, and turn on the fog-lights, all is OK. I turn on the high-beams and the fog-lights turn off, so that's OK. I turn off the high-beams and the fog-lights turn on...however, the high-beams stay on, so there are now 6 lights running. This is because the steady-state voltage on the stock high-beam wire remains around 5-7V, which isn't low enough to turn off the relays on the upgraded wiring.

Should I short the stock high-beam wire to ground with a resistor? If so, what resistor (and wattage resistor) should I use? If I run this resistor, will it cause a problem when the high-beams are turned on and the voltage jumps to 12V? I'm concerned about creating a "short" condition.

It looks to me that there needs to be a pull-down resistor of some sort, which the high-beams were functioning as on the stock wiring. Now that I've upgraded the wiring, the relay doesn't seem to act as a pull-down, and there's voltage on the high-beam wire when it should be around 0-0.1V

The voltage is coming from the fog-light relay. I've changed the fog-light relay and the problem still occurs. What it appears to me is that upgrading the wiring has caused a part of the circuit to become incomplete.

Last edited by 91Z28-350; 11-30-2003 at 11:53 AM.
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Old 11-30-2003, 07:32 PM   #4
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i cant see how upgrading the wires themselves are the cause of this, unless you wired it back together wrong somewhere. so when u go to turn the highbeams off, both beams in the headlights remain on (high and low) along w/ the foglights? are u sure about that? or is it just the highbeams staying on, low beams off, and the foglights on? if its doing that then your high beam switch could just need some adjustment under the dash by the steering column.

can u verify both high and low beams in the sealed headlight are on at the same time?
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Old 11-30-2003, 08:35 PM   #5
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Yes, I'm 100% of the scenario and am positive of why the scenario is happening. Everything is wired as it should be, ground is to ground, low is to low and high is to high. I am just unsure as to how to rectify the problem. I've probed all the lines and the problem is the new high-beam relay is not turning off because of the voltage of the green wire coming from the fog-light relay.

When I move the wires back to the stock configuration, there is no longer a voltage on the stock green wire. My belief is that the high-beam headlamp is acting as a pull-down resistor.

Note the caption at the bottom of this picture near the big "R". It states that the high-beam headlamp is acting as a pull-down resistor. This "resistor" is not apparent in the tech article diagrams probably because there were no factory fog-lights on the vehicle. The green line is left "floating". However, with factory fog-lights, it needs to run to ground indirectly. A direct run to ground will cause a short once the high-beams are turned on.

So, it sounds like I should add a pull-down resistor between ground and the green wire, but what happens when 12V is applied from the headlamp dimmer switch?
Attached Thumbnails
fog light relay--highbeams not turning off-headlights003.jpg  

Last edited by 91Z28-350; 11-30-2003 at 08:46 PM.
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Old 11-30-2003, 08:38 PM   #6
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Here's a diagram of the headlamps.
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fog light relay--highbeams not turning off-headlights002.jpg  
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Old 12-01-2003, 09:10 AM   #7
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the ground for the foglights should be the ground from the highbeam, is that how yours is wired?

Last edited by TekViper; 12-01-2003 at 09:13 AM.
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Old 12-01-2003, 11:20 AM   #8
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Yes, as stock. I'm looking to upgrade my wiring so it will run to a relay instead. I know I need to use a pull-down resistor in place of the high-beam, but I just need validation and some guesses on how big a resistor I should use.
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Old 12-01-2003, 11:45 AM   #9
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u dont need a resistor just wire it up stock. isnt upgrading the wiring just use bigger gauge and new connectors? or completely re-routing the wires? doesnt make sense.
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Old 12-01-2003, 12:54 PM   #10
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One would be nuts to "upgrade" the wiring that way. It's rerouting (upgrading) as stated in the tech-articles to minimize voltage loss by connecting directly to the battery with higher gauge wiring.
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Old 05-13-2006, 08:47 PM   #11
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ok, I just did the upgrade with my ROC and I have the same prob. With the low beams on fogs come on as normal, when I hit the High beams fog lights shut off and four head lights come on. Now when I try to shut off high beams, fogs come on but high beams also stay on even if I just put it to parking light position. I have to turn all off and back on to get regular lights working again or if I plug a high beam light into stock harness lights will act normal. For now I have the low beams on the relay and the high beam is on the factory harness until I can rectify this problem.
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Old 05-20-2006, 04:20 AM   #12
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Anybody???
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Old 07-21-2006, 07:40 PM   #13
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anyone get to the bottomof this issue? I was about to do that headlight harness mod until I read this
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Old 04-23-2009, 09:38 PM   #14
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Re: fog light relay--highbeams not turning off

I'm having this same issue and I'm thinking along the same lines as the pull-down resistor. I am also seeing about 5V on the stock hi-beam circuit after going back to low beams. As everyone else has seen, this is enough voltage to hold the relay high-beam relay on.

Sorry to resurrect such on old thread....but I'm hoping we can put a solution at the bottom.
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Old 04-24-2009, 12:39 AM   #15
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Re: fog light relay--highbeams not turning off

The answer is really simple:
by replacing the headlights with relays (in the stock wiring), you wired a second relay to the ground of the foglight relay. The foglight relay is feeding power to the high-beam relay.
Turn off the foglights and the highbeams will shut off.

Two main options I can think off:
A) cut the light green wire (ground) on the foglight relay and ground the relay.
(However, that would divert from stock behavior and your foglights wouldn't turn off when you turn the high beams on. If you're ok with that, it's the easiest solution.)
B) Cut the light green wire (ground) on the foglight relay and run it from the relay through the firewall to the actual high beam wire (the new upgraded one).
(That's more labor intensive but would retain stock functionality)

There are more options on how to modify the wiring but these are the two main variants and it's too late for me to think of more right now.

Hope this helps.
Lou
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Old 04-25-2009, 08:48 PM   #16
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Re: fog light relay--highbeams not turning off

Thank you for the advice. I'm getting better at electronics, but right now I'm definately more dangerous than knowledgeable. I'm going to go with your option A.

Hopefully, I can get some time to track down the fog light relay tomorrow.
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Old 04-26-2009, 10:48 AM   #17
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Re: fog light relay--highbeams not turning off

On your IROC, the fog light relay should be right by the fusebox, a plastic cube with a standard relay connector.

Lou
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Old 06-05-2010, 11:31 AM   #18
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Re: fog light relay--highbeams not turning off

Option "B" was the answer for me with this problem. Thanks for the help.

Quote:
Originally Posted by BigBadLou View Post
The answer is really simple:
by replacing the headlights with relays (in the stock wiring), you wired a second relay to the ground of the foglight relay. The foglight relay is feeding power to the high-beam relay.
Turn off the foglights and the highbeams will shut off.

Two main options I can think off:
A) cut the light green wire (ground) on the foglight relay and ground the relay.
(However, that would divert from stock behavior and your foglights wouldn't turn off when you turn the high beams on. If you're ok with that, it's the easiest solution.)
B) Cut the light green wire (ground) on the foglight relay and run it from the relay through the firewall to the actual high beam wire (the new upgraded one).
(That's more labor intensive but would retain stock functionality)

There are more options on how to modify the wiring but these are the two main variants and it's too late for me to think of more right now.

Hope this helps.
Lou
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Old 11-03-2014, 10:54 AM   #19
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Re: fog light relay--highbeams not turning off

I know this is an old thread but I recently did the H4 headlight upgrade with relays. I had the same issue with high beams not turning off unless I completely shut the headlights off and then on again. I was getting a small amount of voltage to the high beam trigger wire (the green wire that goes to the high beams). This small amount of voltage was enough to hold the relay on as soon as you shut off the high beams. Looking through the headlight and fog light wiring diagrams and reading many posts then two days later...this solution worked for me.
I chose option "A" that BigBadLou suggested. I wanted my fog lights independent of the high beams. I'm sure glad that I didn't have to add a pull-down resistor like 91Z28-350 did.
Anyway, this worked for me. Thanks for the help guys! Now on to the next project...
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