SR20 Forum banner
1 - 12 of 12 Posts

·
employment whiplash, NC
Joined
·
3,646 Posts
Discussion Starter · #1 ·
I've been trying to resolve my extremely weird problem with my fog lights: http://www.sr20deforum.com/showthread.php?s=&threadid=10068&highlight=Really+weird+problem

The grounds to the fog lights seem good. There's something mounted to the firewall above and to the right of the brake master cylinder. It says "Bosch" on it and has a bunch of wire going in and out of it. It makes nice clickety-click noises when I turn the fog lights on/off. What is this thing and could it possibly be the source of my problem?
 

·
now on the West side!
Joined
·
3,661 Posts
get a picture of it...that might help out :D
 

·
employment whiplash, NC
Joined
·
3,646 Posts
Discussion Starter · #3 ·
Open the hood of your car.
Look at the brake master cylinder.
Now look up and to the right.
It's black, squarish, says "Bosch" and has wires going to it.

Sorry, don't have a digital camera.
 

·
P10 Geek
Joined
·
1,565 Posts
MaddMatt said:
It says "Bosch" on it and has a bunch of wire going in and out of it. It makes nice clickety-click noises when I turn the fog lights on/off. What is this thing and could it possibly be the source of my problem?
You've just described a relay switch. It regulates the power going to your foglights. Here is some basics about it:
BOSCH RELAYS EXPLAINED:
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm
RELAYS AND FOGLIGHTS:
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglites.htm

Sometimes relays will go bad and not work properly. You could possibly pick up a replacement relay just to test your theory. I believe they are quite cheap. I use to buy them for approx. $4.95 when installing alarms a few years ago.
 

·
Seeing red
Joined
·
2,084 Posts
Our Classic fog lights were design afterthoughts of sorts. That's why that relay box looks like it was installed by that one guy who's a friend of a friend of someone your brother thinks he met a while back. A faultless setup from Nissan, I'm sure. :p

Your best bet is to take off the stock driving lights and get quad off-road beams mounted on your hood, WRC style.
 

·
BANNED!!eleven
Joined
·
840 Posts
hahaha...i don't have any foglights and i have been actually thinking of getting a set of hella 500's (i think that's what they are called) and rigging them up to the top of the bumper in a way where i can take them off when i have decided to run some back road. that way i can have lots of light on the backroads around here, but not look like a rally-wanna-be in the morning.
 

·
You're my boy blu!!!!
Joined
·
296 Posts
hey i am aircraft electrician, to me what it sounds like is that your fog lights have a short to ground or high resistance to ground . Depending on how they were installed most were tapped right off the battery. So essentially what is hjappening is the fog lights are drawing a whole bunch of amps off the battery and the alternator which is causing a low voltage problem in your charging and ignition system, causing a low spark situation and unburned fuel. That is my best guess
 

·
Master Cunnilingust
Joined
·
4,713 Posts
Does the relay have four or five wires coming from it? One of them should go to ground, one comes from your switch, one goes to the lights and one will likely have power all the time, or only when the switch is on. You should be able to unplug the relay from the harness and there is probably a number stamped by each brass terminal on the relay. Use a meter to figure out where each wire goes and write down what termial it hooks up to on the relay and e-mail me with your findings and I'll help you out if you'd like.
 

·
employment whiplash, NC
Joined
·
3,646 Posts
Discussion Starter · #11 ·
hey i am aircraft electrician, to me what it sounds like is that your fog lights have a short to ground or high resistance to ground . Depending on how they were installed most were tapped right off the battery. So essentially what is hjappening is the fog lights are drawing a whole bunch of amps off the battery and the alternator which is causing a low voltage problem in your charging and ignition system, causing a low spark situation and unburned fuel. That is my best guess
No more calls please, we have a winner!!!

The fog lights are grounded to the driver's side shock tower. I suppose this ground became corroded a little. I hit everything with a wire brush, re-grounded and viola!!! Runs like a champ again with the fog lights on.

I knew I kept you guys around for something ;)

Something as simple as a bad ground had me completely stumped for 2 months. I now feel stupid and unworthy of my Engineering degree...
 
1 - 12 of 12 Posts
Top