[tech] Upgrade Your LX With Foglights
12-30-2005 | 06:20 PM
#1
[tech] Upgrade Your LX With Foglights
On bypassing the lowbeam dependency for the foglight switch:
Updating the fog light wiring is a good time to upgrade the wiring for the lighting system, and install some relays. Most GT owners suffer from intermittent foglight failure when the switch overheats after being on for long periods of time.
I'm currently examining this on my LX, as I'm about to install some driving lights.
The following is my planned approach; I'm hoping to work on it once we get some warm weather (and this darned snow starts melting!).
Since my headlights work fine now, and I want to avoid the dreaded intermittent light problem, I'm going to install a relay for the foglights only. So far, the simplest way I've found to wire this up is:
1) run 12V continuous to the foglight switch on the same wire as the one that supplies 12V to the headlight switch (#38 BK/O - 12) (i.e. circuit #38, black w/ orange stripe, 12 ga wire).
2) run the output of the foglight switch to the 12V coil input on the relay (DIN 86). Run the relay coil ground (DIN 85) to the same ground as the headlight switch (#57 BK - 20).
3) use the spare fuse socket #12. It appears to lie on a "power bar" run off of cct #38 BK/O - 12 (note that this is NOT the same cct as the #38 cct mentioned above, although it does supply power to it).
(as an alternative, you could use the same foglight fuse socket (#15), but instead of using fuse input cct #13 R/BK - 16, you could patch in #38. If you did this, you then could run the output of fuse #15 (#477 T/O - 20) directly to the 12V power input to the relay (DIN51)).
4) run the output of fuse socket #12 to the 12V power input to the relay (DIN 51).
5) connect cct #478 T/O - 20 (used to be the output of the foglight switch) to the 12V output of the relay (DIN 87).
Note that this circuit hacking still uses the same 20 ga wire to drive the foglights. I'm not sure what the current draw of the factory foglights are, but I'll make the assumption that they don't exceed the current carrying capacity of a 20 gauge wire (otherwise Ford wouldn't have used it, right? :-).
Updating the fog light wiring is a good time to upgrade the wiring for the lighting system, and install some relays. Most GT owners suffer from intermittent foglight failure when the switch overheats after being on for long periods of time.
I'm currently examining this on my LX, as I'm about to install some driving lights.
The following is my planned approach; I'm hoping to work on it once we get some warm weather (and this darned snow starts melting!).
Since my headlights work fine now, and I want to avoid the dreaded intermittent light problem, I'm going to install a relay for the foglights only. So far, the simplest way I've found to wire this up is:
1) run 12V continuous to the foglight switch on the same wire as the one that supplies 12V to the headlight switch (#38 BK/O - 12) (i.e. circuit #38, black w/ orange stripe, 12 ga wire).
2) run the output of the foglight switch to the 12V coil input on the relay (DIN 86). Run the relay coil ground (DIN 85) to the same ground as the headlight switch (#57 BK - 20).
3) use the spare fuse socket #12. It appears to lie on a "power bar" run off of cct #38 BK/O - 12 (note that this is NOT the same cct as the #38 cct mentioned above, although it does supply power to it).
(as an alternative, you could use the same foglight fuse socket (#15), but instead of using fuse input cct #13 R/BK - 16, you could patch in #38. If you did this, you then could run the output of fuse #15 (#477 T/O - 20) directly to the 12V power input to the relay (DIN51)).
4) run the output of fuse socket #12 to the 12V power input to the relay (DIN 51).
5) connect cct #478 T/O - 20 (used to be the output of the foglight switch) to the 12V output of the relay (DIN 87).
Note that this circuit hacking still uses the same 20 ga wire to drive the foglights. I'm not sure what the current draw of the factory foglights are, but I'll make the assumption that they don't exceed the current carrying capacity of a 20 gauge wire (otherwise Ford wouldn't have used it, right? :-).
01-09-2006 | 07:25 AM
#2
Junior GTcars Poster
Joined: Dec 2005
Posts: 347
Rep Power: 697 
This here isn't necessarily so you can install fog lights on your LX, though it does cover that in essence. All 87-93 Mustangs come with the fog light wiring intact. You are (LX) however missing a foglight switch and fuse, and obviously the fog lights. This also sheds some light on allowing your fog light equipped GT to have the fog lights on with the parking lights on, instead of only with the headlights on. Personally, I would suggest upgrading to a thicker gauge wire than the 20ga used by the factory as that is not even close to thick enough. You will want to use at least a 12 ga lead.
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