Why do I need the passing control relay?

[Mike7447]

I figured out my headlight issue.

#1. I am an idiot.

i had the male headlight harness plugged into the wrong female socket.

unfortunately, I managed to kill the passing relay while trying to bypass junk. 
if all this thing does, is raise the headlight doors and allow me to flash someone I intend to pass, then I can forego using it. It appears a new one is about 100 bucks.

i know I can jumper headlight function simply by combining the blue/red, and the blue/yellow wire that goes to this relay and get the 95% function that I need, and when I decide to cough up a hundred bucks, unplug that jumper,I just want to be sure that’s all it does. 
 

[psu_Crash]

I'm guessing by this point you have just bypassed it an moved on? I'm also curious to see if it has any other functions. 

Good find on the harness plug! I have done similar things, even when checking wire colors ... that don't really resemble the original color anymore. 

[TSITy]

The passing control relay (plugged into B-39 to the left of the glove box behind the dash) is primarily comprised of circuitry to raise the headlights. The reason it looks so complicated is because of the theft alarm circuit that is built into it. The ECU (this is really the ETACS computer under the driver seat, it is sometimes referred to as ECU in the schematics) can activate the headlights to raise and flash when the car decides it is being stolen (there's lots of ways to trigger it). 

I can break the pinout down if you really want me to, but that's the gist of it. These cars are pretty easy to steal regardless, so there's not much harm done in removing the anti theft headlight flashing feature. 

If you ctrl-f in the electrical schematics on the phrase "passing control relay", it describes this anti theft feature in great detail. 

I would certainly not waste $100 on a replacement and wire in a suitable relay with a plug of your choice. It really doesn't matter. Just make sure it's a common part that isn't NLA or discontinued. Any time I have a part like this fail on one of my cars, I find a suitable part that is readily available and install it. I have not had to do this with the passing control relay as I have several spares. When the day comes, it will be cut out.

 

Edited December 4, 2024 by TSITy

[Mike7447]

On 12/4/2024 at 4:55 PM, TSITy said:

The passing control relay (plugged into B-39 to the left of the glove box behind the dash) is primarily comprised of circuitry to raise the headlights. The reason it looks so complicated is because of the theft alarm circuit that is built into it. The ECU (this is really the ETACS computer under the driver seat, it is sometimes referred to as ECU in the schematics) can activate the headlights to raise and flash when the car decides it is being stolen (there's lots of ways to trigger it). 

I can break the pinout down if you really want me to, but that's the gist of it. These cars are pretty easy to steal regardless, so there's not much harm done in removing the anti theft headlight flashing feature. 

If you ctrl-f in the electrical schematics on the phrase "passing control relay", it describes this anti theft feature in great detail. 

I would certainly not waste $100 on a replacement and wire in a suitable relay with a plug of your choice. It really doesn't matter. Just make sure it's a common part that isn't NLA or discontinued. Any time I have a part like this fail on one of my cars, I find a suitable part that is readily available and install it. I have not had to do this with the passing control relay as I have several spares. When the day comes, it will be cut out.

 

Well thanks for that… I decided to buy a used one from Steve Sutherland, as well as a few other clips and assorted doo-dads. 
In reality, I could give a rats red bunion hole if I’m not able to flash someone prior to passing them, but for 25 bucks used, I figure WTH…I prefer to actually have the completed circuit as opposed to a janky single wire jumper. 

[Mike7447]

On 12/4/2024 at 4:55 PM, TSITy said:

The passing control relay (plugged into B-39 to the left of the glove box behind the dash) is primarily comprised of circuitry to raise the headlights. The reason it looks so complicated is because of the theft alarm circuit that is built into it. The ECU (this is really the ETACS computer under the driver seat, it is sometimes referred to as ECU in the schematics) can activate the headlights to raise and flash when the car decides it is being stolen (there's lots of ways to trigger it). 

I can break the pinout down if you really want me to, but that's the gist of it. These cars are pretty easy to steal regardless, so there's not much harm done in removing the anti theft headlight flashing feature. 

If you ctrl-f in the electrical schematics on the phrase "passing control relay", it describes this anti theft feature in great detail. 

I would certainly not waste $100 on a replacement and wire in a suitable relay with a plug of your choice. It really doesn't matter. Just make sure it's a common part that isn't NLA or discontinued. Any time I have a part like this fail on one of my cars, I find a suitable part that is readily available and install it. I have not had to do this with the passing control relay as I have several spares. When the day comes, it will be cut out.

 

Which electrical schematic allows me to control f? I have been using an actual service manual for all of my schematics.

[TSITy]

7 hours ago, Mike7447 said:

Which electrical schematic allows me to control f? I have been using an actual service manual for all of my schematics.

http://www.starquestgarage.com/manuals/service/conquest/1988/88_conquest_service_nav.html

click electrical and download. This is 88 only so if you have a different model it will be different. If you have an 87, a lot of things are the same.