fog lights

Uh, did you guys miss my post that we should be able to jumper the SB wire on pin 13 at the ECU to the yellow wire at pin 17 on the ECU? That should still allow the OEM fog switch to turn on the fog without headlights, though you still need tailights, as the fog relay gets its coil power from the taillights. Turns out power coming from the taillight fuse is switched by the ECU with a relay.

 

Jayman wrote
"You could wire the real foglights on a separate circuit, and put the headlight switch to Park. I'm not sure if that would be legal in the U.S. or Canada though."

with DRL's we still have the problem of them coming on when the car go's "Ready" I suppose a double pole double throw relay in the circuit to extinguish the DRL's and power the fog's might work. In bad fog I turn the headlighs to Park and just drive on the reduced light from the DRL's. Actually better than the fog's.

 

"DanMan32" Uh, did you guys miss my post that we should be able to jumper the SB wire on pin 13 at the ECU to the yellow wire at pin 17 on the ECU? That should still allow the OEM fog switch to turn on the fog without headlights, though you still need tailights, as the fog relay gets its coil power from the taillights. Turns out power coming from the taillight fuse is switched by the ECU with a relay.

DanMan32, A question from the Electrically Ignorant, Do I understand that jumpering pin 13 and 17 on the body ECU will only trigger an event and not add any load to either circuit during the time the fogs are on?

 

The fog light switch's ground side is actually fed by a switch in the dimmer for low beam. If you go high beam, the switch loses its ground, so normally the ECU loses its fog signal, though it will disable it anyway internally. So if we jumper over the ECU, the fogs will still turn off on high beam, though I don't see why they made it illegal to have fogs with high beams.

 

Danman32 said"though I don't see why they made it illegal to have fogs with high beams." it has to do with total candle power output.

 

The European Priuses are wired differently. They all have rear foglights, and front foglights are optional.

If the front foglights are fitted, they can be turned on whether you're on parking lights, headlights or full beam. The rear fogs can be turned on whenever the front fogs are on.

If the front foglights aren't fitted, then the rear fogs can only be turned on when the headlights are on.

 

I just got the geekmobile back from the dealer, having my electrochromic HomeLink mirror and fog lights installed.

The actual lamps may or may not be Toyota original equipment, but they did a good install job, using the proper OEM grill pieces on both sides to duplicate the built-in mounting of factory fogs.

The switch to activate them is NOT an inner ring on the headlight stalk as shown in the manual. Instead it is a small round rocker-toggle, with tiny red LED built in, that is mounted right next to the panel dimmer control, in the blank rectangular space reputedly used for EV mode switch in EU and Japan.

The lights are white, not amber, but are fairly bright, and aimed very low. Actually, they are currently aimed TOO low, brightly illuminating the ground in front of the car, but so close to the front bumper that you have to lean forward to see it. I don't think there should be any trouble re-aiming them just a bit further forward, and they should be valuable in rain and fog, or simply as DRLs

And here's the best part: They wired them CORRECTLY (in other words not like the factory), which makes me suspect that my salesman did not have them done at the dealer, but jobbed them out to a local speed shop. They can be turned on with parking lights only, with head lights only, and turn off when high beams are activated (that's a state requirement). They also turn off automatically along with the other external lights when the driver door is opened.

Anyway, it's proof that the fogs CAN be wired up properly. We likesss our precious fogs, yesssss, we doesssss.

 

Sounds like they pulled power from the tail light fuse, at least for the relay coil. Good move. I'd like to know how they set it up to turn fogs off with high beams. Maybe they took ground from the dark blue wire, which provides ground in low beam from the dimmer?

 

Well, as it turns out, so would I.

I double checked by actually looking (instead of watching the lights shine on the garage door and guessing) and discovered that they screwed up, and the fogs do NOT go off with the high beams.

So, I'll have to go yell at the salesman. But I'm afraid if I do, they'll just wire it to the low beams. Maybe I could "help" them fix it right. Worst case they'd have to add another relay, normally closed, with the coil powered by the high beams.

But what's that dark blue wire again? That may have promise.

I'm presuming that the fogs are wired through a normally open relay, and as you say, the hot side of the coil is wired to the taillight fuse. So then what I'd need on the ground side of the coil is a terminal that's grounded during parking, and low beams, but not grounded during high beam operation, and "don't care" when the lights are off.

Is that what the dark blue wire does? (I can see I'm going to have to have the wiring diagrams before long.)

At least the HomeLink device worked, right out of the box. I have an ancient Stanley opener from the early '80s and I was afraid it wouldn't.

 

With fog, there is a dark blue wire on the combination switch connector, pin 16. It connects to an orange wire heading back to the combination switch for the fog light switch, which then connects to a sky blue wire, which goes to the body ECU.

If the blue wire is not there, they can tap pin 16, and use the ground it provides on low beams, and sent it to the aftermarket switch they provided.

 

OK, this should ease some curiosity

 

gmurphy seems to have successfully devised a method to turn the fog lights on without the headlights.

How to turn on Daytime running light system?

 

What fog lights?

Those are really nothing more than accent lights in the front.

REAL fog lights would be switched to be manually turned on and off and would be amber.

Just what is that switch location immediately to the right of the dimmer switch? I have a cutout plugged port there, but no switch.

ya know, that could be rewired direct to the 12 volt auto battery and install a manual switch, disconnecting the existing wiring setup and install true fog lamps. That is how Junior Sample did it around these parts.

HeeHaw

 

If you look on the wiring diagram I posted, you can tap into pin 16 of the combination switch and use its ground output to feed your fog switch. When the dimmer is on high beam, your switch loses ground, the relay loses ground, and the fog lights are turned off.
If your fog switch is bridging the tail fuse and the fog relay, with the other end of the fog relay conneted directly to ground, either change that, or else yes, you will need another relay.

 

This sounds good. Do you intend to do it?

Also, I assume that feeding power to pin 13 of the ECU can't hurt anything (right?). That is, when the switch is set to high beams.

Finally - the real question - where is the body ECU, how does one access it, and do you have any recommendations for where/how to place the jumper?

 

I should check that when the ECU turns off the fog relay, that the output is open collector, rather than B+. Second possible concern is if the switch and wiring can handle the current of the fog relay coil.

I haven't opened the dash that far, but I believe the ECU is part of the main junction block. The driver's side of the dash that is.