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Old 05-14-2018, 11:16 PM   #1
VolvoMan1990
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Default My Fog Lights work now, but did I wire them wrong?

See wiring diagram I drew below. I mixed the diagrams from the Hella instructions and the OEM Volvo 240 instructions.

I was originally going to tap into the headlight wire, but when I tested it, it didn't work.

With how it's wired now, the fog lights can work with the car on or off, key in or out. Which I'm technically fine with, but I'm wondering if I'm running any risks of frying anything.

One thing to note, terminal 30 has a 30A fuse integral into housing.


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Old 05-15-2018, 11:51 AM   #2
Khrrck
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I'm assuming the bottom line with the 85-86-87-30 terminals is a relay.

What are the two small boxes above the battery?

It looks like you've tied both pin 2 and 3 on the switch to ground, is that correct? I think that prevents the switch lighting from coming on.

Overall, it looks OK. I'd make sure the switch is on fused power too. Personally I'd run power to the switch off one of the key-only fuses in the fusebox, so you don't accidentally leave the lights on.

This diagram shows the foglight relay being powered off of the 56b terminal on the high beam relay near the battery. I *think* this is supposed to make them turn on and off with the low-beam headlights, but I can't puzzle out how it works without spending more time than I ought to at work. Is this what you tested when "tapping into the headlight wire"?
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Old 05-15-2018, 11:54 AM   #3
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Actually, the most useful bit of info would be knowing which pin on your switch is which. Two of them are for the lightbulb and two of them are for the switch, and your diagram isn't super clear on which ones are connected to what.
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Old 05-15-2018, 12:08 PM   #4
VolvoMan1990
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Actually, the most useful bit of info would be knowing which pin on your switch is which. Two of them are for the lightbulb and two of them are for the switch, and your diagram isn't super clear on which ones are connected to what.
Switch:
Pin 2 is switch ground
Pin 1 is power output
Pin 3 is (-) for light bulb
Pin 4 is (+) for light bulb

So when the switch is switched, the internal mechanism closes the circuit between pins 1 and 2 (-) and since pin 3 is connected to pin 1, switching the switch also closes the circuit between pins 2 and 3 effectively giving the light bulb a ground and thus turning it on. Also therefore, when the switch is switched, pins 1 and 2 are closed, the relay also gets ground via the pin 1 and 2 connection.

I've also just realized that I've made it a ground switched system. If you see, the signal for relay is always fed (+) since it's connected to (+) via the 86 terminal and switch pin 4 terminal 2 in 1 plug to battery (+). It's missing ground until the switch is switched and the switch terminals 1 & 2 are bridged. Is that bad?

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I'm assuming the bottom line with the 85-86-87-30 terminals is a relay.

What are the two small boxes above the battery?

It looks like you've tied both pin 2 and 3 on the switch to ground, is that correct? I think that prevents the switch lighting from coming on.

Overall, it looks OK. I'd make sure the switch is on fused power too. Personally I'd run power to the switch off one of the key-only fuses in the fusebox, so you don't accidentally leave the lights on.

This diagram shows the foglight relay being powered off of the 56b terminal on the high beam relay near the battery. I *think* this is supposed to make them turn on and off with the low-beam headlights, but I can't puzzle out how it works without spending more time than I ought to at work. Is this what you tested when "tapping into the headlight wire"?
Yes, the bottom 85-86-87-30 is a relay.

Two boxes are an insulated spade plug (Male & Female).

That's a good point on the switch being on fused power. Right now, it's just straight to the battery. I might put an inline fuse between pin 4 on the switch and the battery. I don't think I'd leave the lights on since I'd be able to see the bright fog light symbol illuminated on my dash telling me I've left them on. Kind of like a lights on warning light.

When I tested them off the OEM diagram, it had me tap into the 56a circuit which is the low beam headlight wire. This way, whenever the low beams are on, the relay and switch get signal. I tried testing that, but it didn't work at all.
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Old 05-15-2018, 12:33 PM   #5
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This post should explain how the signal from the headlight relay is supposed to work. There are early and late wiring diagrams and they use the headlight relay differently.

http://forums.turbobricks.com/showpo...5&postcount=19
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Old 05-15-2018, 12:40 PM   #6
VolvoMan1990
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Originally Posted by hiperfauto View Post
This post should explain how the signal from the headlight relay is supposed to work. There are early and late wiring diagrams and they use the headlight relay differently.

http://forums.turbobricks.com/showpo...5&postcount=19
Ahh! This is extremely insightful, thank you. Yes, I used the top diagram to wire them.

I attempted to tap into the 56a Low Beam wire to the H/L relay, but it didn't work to turn on the fog lights or the switch light.
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Old 05-15-2018, 01:54 PM   #7
Khrrck
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Having a ground-switched system works - I believe the horn is ground-switched - but can be more difficult to diagnose.

From your explanation of your switch wiring, though, it seems like you've wired the relay signal through the lightbulb. This means your foglights will go out if the bulb in the switch burns out.

The 56a vs 56b vs plain ground thing seems to depend on whether you want your foglights on only with the low beams, the high beams, or independent.

IMO, I would suggest the following changes:

- Rewire the relay as follows:
* Terminal 85 to the switch.
* Terminal 86 direct to ground or to the appropriate terminal on the headlight step relay.
* Optionally, an extra wire can be added from Terminal 87 to the fog-light switch, so a relay or fuse failure will cause the fog-light indicator to go out. This seems to be the stock configuration.

- Rewire the switch as follows:
* Pin 1 to key-fused power. You can use an existing fuse in the fusebox for this.
* Pin 2 to Terminal 85 on the the fog-light relay.
* Pin 3 to Pin 4 OR to Terminal 87 on the fog-light relay.
* Pin 4 to ground.

Please double-check my work since I'm just doing this in my head based on the diagrams available. This should accomplish the following things:

* Fog lights turn off when key is off.
* Switch circuit of the relay is not ground switched.
* Switch circuit of the relay is fused.
* Switch circuit of the relay is not dependent on a functional light-bulb.
* Optional: Fog-light switch bulb is off if relay has failed or fuse has blown.
* Optional: Fog-light control depends on the state of the headlights.
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Old 05-15-2018, 02:55 PM   #8
VolvoMan1990
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Originally Posted by Khrrck View Post
Having a ground-switched system works - I believe the horn is ground-switched - but can be more difficult to diagnose.

From your explanation of your switch wiring, though, it seems like you've wired the relay signal through the lightbulb. This means your foglights will go out if the bulb in the switch burns out.

The 56a vs 56b vs plain ground thing seems to depend on whether you want your foglights on only with the low beams, the high beams, or independent.

IMO, I would suggest the following changes:

- Rewire the relay as follows:
* Terminal 85 to the switch.
* Terminal 86 direct to ground or to the appropriate terminal on the headlight step relay.
* Optionally, an extra wire can be added from Terminal 87 to the fog-light switch, so a relay or fuse failure will cause the fog-light indicator to go out. This seems to be the stock configuration.

- Rewire the switch as follows:
* Pin 1 to key-fused power. You can use an existing fuse in the fusebox for this.
* Pin 2 to Terminal 85 on the the fog-light relay.
* Pin 3 to Pin 4 OR to Terminal 87 on the fog-light relay.
* Pin 4 to ground.

Please double-check my work since I'm just doing this in my head based on the diagrams available. This should accomplish the following things:

* Fog lights turn off when key is off.
* Switch circuit of the relay is not ground switched.
* Switch circuit of the relay is fused.
* Switch circuit of the relay is not dependent on a functional light-bulb.
* Optional: Fog-light switch bulb is off if relay has failed or fuse has blown.
* Optional: Fog-light control depends on the state of the headlights.
The suggestion is extremely interesting, thank you for it!

What if, though, instead of changing around a few terminals, we instead focus on Terminal 4 of the switch and terminal 86 of the relay.

So run Relay Terminal 86 straight to Fuse #1 which is hot only in run or start. Then run Terminal 4 to Fuse #8 which is hot at all times.

I'm also thinking off the top of my head, but this should accomplish the following:
* The fogs will now only work with the key on, which is good, that's a feature I like of the headlights that if I leave them technically on with the car off, it won't drain my battery.
* But the fogs will still be independent of low/high beam headlights
* Relay Terminal 86 is now getting a fused connection to the battery.
* Terminal 4, and therefore the light, are now independent of the relay, so if the light goes out the relay can still work as long as the switch is switched.
* Terminal 4 also has a fused connection and now the fog light switch light is out of the troubleshooting picture if the fog lights should for some reason fail to turn on.

In thinking more about it, not sure if that would totally work. But if we think about the whole system as a whole as configured today, if the fog lights don't work then it can only be three possible causes right?:
* Fog light bulbs bad
* Fog light switch bulb bad
* 30A integrated relay on terminal 30 has blown.

Those would be the only reasons right? So for the purpose of simplification, it's actually quite simple and is easy to troubleshoot if anything goes awry, correct?

Last edited by VolvoMan1990; 05-15-2018 at 03:53 PM..
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Old 05-15-2018, 03:49 PM   #9
Khrrck
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That's an improvement because everything is now fused. And looking at it again, I was confused by the ground-switched circuit - your current setup has independent paths for the relay and lightbulb as is.

Just change the connection circled in red so that it's connected to key-hot fused rather than direct to battery, and you'll be good to go. The setup may confuse any mechanic who works on the car later, but I doubt that's a problem. ^^

No need to connect to different fuses like you were thinking - the only difference would be the fog-light indicator staying on while the car is off, which could be confusing since the foglights are actually off at that point.

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Old 05-15-2018, 03:57 PM   #10
VolvoMan1990
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Nice! Great catch with the terminal 4 to fuse 8 (always hot). Didn't even think of the scenario where the car would be off but the fog light switch light still on. That would definitely confuse me.

Here's a new diagram based on the counter recommendation I made and the confirmation you offered:


Untitled
by Volkswageneer1990, on Flickr

Everything now looks good right?
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Old 05-15-2018, 04:13 PM   #11
Khrrck
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Looks great!
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Old 05-16-2018, 10:50 AM   #12
VolvoMan1990
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Looks great!
Great! Thanks for all the help!!
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