Fog light switch in my cab isnt getting a 12V constant

[Deleted]

So thanks to @eaglescout526 I got myself some fancy new Hella 550 lights. However after getting them all wired up I realized they only come on with my highbeams. No problem that just means I had the terminal in the wrong slot on the harness, so I pulled it out and plugged it into the right one, only now they don't come on at all. I know theyre working because they come on when plugged into the highbeams slot on the harness, so I took a volt meter and tested the slot thats connected to the switch in the cab. The reader beeped when the switch was on and stopped when I flipped it off, so this tells me that it is making a complete circuit. However when I check to see what kind of voltage its reading at, nothing comes through at all. So I know my lights work, I know the switch works, but the switch isnt getting the power it needs to flip the relay to give the lights power. Any advice on where to look to get this fixed would be helpful, Its also worth noting I'm using a 1996 XJ fusebox and harness setup. 

[eaglescout526]

I’m pretty stumped on this too. I’ve been talking with him for a while on this issue and he addressed it today. Granted he’s all the way on the other end of the valley so I can only go off of what I know. I think he’s not getting any power at the switch to send down the line to the lamps, so I think there’s something wrong between the PDC or battery to the switch itself. The LED on the switch does not light up at all to indicate power when the headlights are on. Anyone got anything?

[Eagle]

There's a link to the 1988 electrical manual on this site somewhere. Find that and study it -- the '86 should be pretty much the same, although wire colors might be different.

 

What you need to know is that AMC wired fog lights so that they ONLY come on with the low beam headlights. They did not operate if you only had the parking lights on, and they did not operate when the high beams were on. (That part is federal regulation -- fog lights MUST turn off when the headlights go to high beam.)

 

If your fog lights only operate when the high beams are on, something is wired backwards. I assume there is a relay somewhere in the circuit. If so, I suspect that you need to find terminals 87 and 87A on the relay, and move that connector from whichever it's on to the one that's empty.

 

 

[Deleted]

1 hour ago, Eagle said:

There's a link to the 1988 electrical manual on this site somewhere. Find that and study it -- the '86 should be pretty much the same, although wire colors might be different.

 

What you need to know is that AMC wired fog lights so that they ONLY come on with the low beam headlights. They did not operate if you only had the parking lights on, and they did not operate when the high beams were on. (That part is federal regulation -- fog lights MUST turn off when the headlights go to high beam.)

 

If your fog lights only operate when the high beams are on, something is wired backwards. I assume there is a relay somewhere in the circuit. If so, I suspect that you need to find terminals 87 and 87A on the relay, and move that connector from whichever it's on to the one that's empty.

 

 

Thanks Ill be sure to look at that, but the fogs only come on when theyre plugged into that certain port on my harness. When theyre plugged into the port thats connected to the switch in my cab they don't come on at all.

[AZJeff]

I always wire any auxiliary lights to be “hot” whenever the parking lights are on.   I do this by feeding the relay control switch from the feed to the parking lights themselves.

 

of course, this means you have to make sure any aux. lights that are not compliant with your local and state laws are switched off when you are on paved roads...

[Deleted]

2 hours ago, AZJeff said:

I always wire any auxiliary lights to be “hot” whenever the parking lights are on.   I do this by feeding the relay control switch from the feed to the parking lights themselves.

 

of course, this means you have to make sure any aux. lights that are not compliant with your local and state laws are switched off when you are on paved roads...

hmm I'm not sure i follow, so you splice a wire into the parking lights wire so when theyre on the switch is being fed power?

[AZJeff]

8 hours ago, Pirate_Staz said:

hmm I'm not sure i follow, so you splice a wire into the parking lights wire so when theyre on the switch is being fed power?

I tap into the power that feeds the parking lights.   That new power wire feeds the switch(es) that control the relay(s) that power any auxiliary lights.

 

Doing this means that the auxiliary lights automatically shut off whenever the parking lights are off, even if the auxiliary light switches are in the "on" position.  

[Eagle]

14 hours ago, AZJeff said:

I always wire any auxiliary lights to be “hot” whenever the parking lights are on.   I do this by feeding the relay control switch from the feed to the parking lights themselves.

 

of course, this means you have to make sure any aux. lights that are not compliant with your local and state laws are switched off when you are on paved roads...

 

I think it makes perfect sense for fog lights to operate with the parking lights, even if the headlights are off -- but that's not the way AMC/Jeep wired them. The problem with wiring them to the parking lights is that the law requires that fog lights go off when the headlights are switched to high beam. There is a solution to that -- it requires a second relay in the fog light circuit, wired so the fog light circuit is interrupted when the high beams come on.

[eaglescout526]

What I’m curious about is how different is the 96 XJ harness to just not give any power to the switch? Everything else on that headlight bulk head works except power to the switch to go to the lights. Unless such wasn’t wired right or there’s a fuse or relay that is bad somewhere. 

[AZJeff]

23 hours ago, Eagle said:

 

I think it makes perfect sense for fog lights to operate with the parking lights, even if the headlights are off -- but that's not the way AMC/Jeep wired them. The problem with wiring them to the parking lights is that the law requires that fog lights go off when the headlights are switched to high beam. There is a solution to that -- it requires a second relay in the fog light circuit, wired so the fog light circuit is interrupted when the high beams come on.

Eagle, you and I have talked about this issue on this forum in the past.   Yes, most state motor vehicle codes limit how much light you can have projected from the front of the vehicle.

 

However, there are times and places where some drivers would want more illumination, such as in the rural areas here in Arizona.  It gets REALLY dark out here away from towns, and I, for one, want all the illumination I can get, whether I am driving on paved roads or on forest service trails.

 

The key, of course, is to use common sense.   If you are driving whether there is other traffic, don't use auxiliary lighting, since it might blind other drivers.  Stick to the factory lamps, and use them accordingly (dimming the brights, etc.)

 

I also suspect that there is a difference in law enforcement attitude to extra lighting in various parts of the country.   Out in rural areas, it's recognized that added lighting is actually a safety benefit, assuming you are using it away from other vehicles, and a police officer wouldn't do much about someone running a light bar or whatever, as long as you used it like one would their high beam headlights.

[Deleted]

On 11/23/2019 at 11:23 AM, AZJeff said:

However, there are times and places where some drivers would want more illumination, such as in the rural areas here in Arizona.

 

The key, of course, is to use common sense. 

Pretty much this, I only plan on using them when I'm camping or offroading at night. I think I won't worry about the switch right now and just have it wired so that they come on with my highbeams as the only time I would have those on is if I'm doing the previously stated activities. After following the leads from the switch in my dash down to the fuse box it looks like the terminal was never installed or removed so I think if I want power to that switch Ill have to figure out how to get all that back. No big deal in the end my truck is in need of rewiring badly so maybe once I get around to that Ill fix it.

[Eagle]

On 11/23/2019 at 1:23 PM, AZJeff said:

The key, of course, is to use common sense.   If you are driving whether there is other traffic, don't use auxiliary lighting, since it might blind other drivers.  Stick to the factory lamps, and use them accordingly (dimming the brights, etc.)

 

 

Promising yourself to always use common sense doesn't make an illegal setup legal, although it may reduce your chances of being caught and ticketed.

 

I understand what you're saying about wanting more light in rural locations, but I don't think fog lights are the answer for that. Fog lights don't project very far ahead, they throw most of their light low and wide, to the sides of the road. In my younger days, when I did a fair amount of night driving when the Interstates weren't as heavily traveled as they are today, I ran driving lights on my cars, and they made a huge difference. Back then, there weren't any laws governing how/when driving lights could operate, so I just controlled them with a toggle switch to the relay. Now the law for driving lights is just the opposite of fog lights: fog lights have to go OFF when the high beams come on; driving lights can ONLY operate when the high beams are on.

 

For maximum flexibility and visibility, I would want a pair of each, wired properly.

[AZJeff]

4 hours ago, Eagle said:

 

Promising yourself to always use common sense doesn't make an illegal setup legal, although it may reduce your chances of being caught and ticketed.

 

I understand what you're saying about wanting more light in rural locations, but I don't think fog lights are the answer for that. Fog lights don't project very far ahead, they throw most of their light low and wide, to the sides of the road. In my younger days, when I did a fair amount of night driving when the Interstates weren't as heavily traveled as they are today, I ran driving lights on my cars, and they made a huge difference. Back then, there weren't any laws governing how/when driving lights could operate, so I just controlled them with a toggle switch to the relay. Now the law for driving lights is just the opposite of fog lights: fog lights have to go OFF when the high beams come on; driving lights can ONLY operate when the high beams are on.

 

For maximum flexibility and visibility, I would want a pair of each, wired properly.

Actually, I have both driving lights and fogs on my MJ.  The fogs are for illuminating the sides of trails and the large rocks on them.  The driving lights are more for the rural highways.

 

I suspect that AZ law enforcement are a bit more lenient on aux. lighting as opposed to back East, as long as one is not a complete jerk about when/where one uses that added illumination.

[Deleted]

On 12/6/2019 at 5:41 PM, AZJeff said:

Actually, I have both driving lights and fogs on my MJ.  The fogs are for illuminating the sides of trails and the large rocks on them.  The driving lights are more for the rural highways.

 

I suspect that AZ law enforcement are a bit more lenient on aux. lighting as opposed to back East, as long as one is not a complete jerk about when/where one uses that added illumination.

Yup theres people all the time who drive with those lights on (mostly lifted trucks that don't know what theyre doing) But I'm still smart enough to only use em when I'm camping or on the interstate. Along with that the tint laws here are pretty lax as well. The church I used to work for had an officer on campus during services and so I asked him about tint once because my Tacoma was "more than the legal limit" and he said they really don't stop anyone specifically for tint since the sun is so bright around here but if you get pulled over for speeding or something it can be something they decide to hit you for if youre just being a jerk to them about the situation. 

[DesertRat1991]

Is it really important to you to maintain the stock wiring?  If not, you could probably bypass the stock setup with much less headache.

 

I used this $10 harness for my aux lighting: MICTUNING MIC-B1002.  It's good to 40A and comes with fuse, relay and switch.   You can replace the switch with any style you like -- possibly even the OEM switch if it uses standard spade connectors.

 

Regarding the legalities, when I lived back east I recall that the state conducted annual DOT safety inspections as part of vehicle registration renewal.  The inspection station checked things such as airbags, lighting, seat belts and even wiper blades.   There is no such thing in the state of Arizona.   No one is ever going to look in to how OP's fog lights are wired up.

[Deleted]

On 12/30/2019 at 12:32 PM, DesertRat1991 said:

Is it really important to you to maintain the stock wiring?  If not, you could probably bypass the stock setup with much less headache.

You assume the previous owner of my comanche hasnt already hacked it up and combined it with an XJ harness resulting in tons of electrical issues lol. That kit you linked may be the answer to my problem!