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Re: Replace just the lenses, not the entire headlight Posted by Larry West [Email]  (#1140)  [Profile/Gallery]
(more from Larry West) on Fri, 12 Jun 2009 10:42:21
In Reply to: Re: Replace just the lenses, not the entire headlight, pants, Fri, 12 Jun 2009 08:13:38 Members do not see ads below this line. - Help Keep This Site Online - Signup |
First let me say that you DO want a separate switch for the driving lights, and separate wiring, and separate fusing.
For the switch, look for an NG900/9-3 "rear fog light" switch. It will have the rounded corners you need, and an icon that works, if you use the switch "upside down".
For the wiring, either use the kit that comes with the lights, or make one up yourself. Running the driving lights off of the high beam circuit, and only one of them at that, is at the least inefficient, and at worst, could cause the wire to overheat and cause a fire. The driving lights must have their own relay to power the lights. The relay coil is attached to the switch (more in a sec...), and the switched contacts are wired from the battery, via a fuse to the relay input terminal (30), and then out from the relay (terminal 87, IIRC). From there, I also recommend a fuse on each line, and then to the lights.
Never run the lights with only a switch between the battery and the lights.
Now about the coil wiring for the relay. In most Saabs with Halogen lights, the fog light relay coil is grounded (terminal 85) via one of the high beam filaments. The current (+12v) from the switch comes in on terminal 86. The low current of the relay coil precludes the high-beam bulb from lighting. When you switch on the high beams, the relay then sees +12v at both coil terminals, and the relay drops, shutting off the fogs. You can apply the same functionality here by grounding the driving light relay via a low beam filament. This would need to be done close to the bulb on a 9-5, as you don't want to upset the bulb warning system operation. And don't ask me about how to adapt it to the Xenons!
Second thing about relays. If you hunt around enough, you would find that there are several different types of those little square relays. Some are four terminal, and are called "SPST" Single Pole, single throw. All they do is make or break the circuit. A "normally open" kind makes the circuit when the coil is energized, and a "normally closed" type opens the circuit when the coil is energized.
Then there are five-terminal variations. One is a "SPDT" Single pole, double throw. This relay can switch current between two connections (terminal 30 to either terminal 87 or 88), depending on whether the coil is energized.
The next two are variations on the same thing. Basically, one input terminal (30), goes to two output terminals (usually 87 & 87a). The difference is in the diagram on the top or side. One type splits the current after the relay contact. The other splits the current through two relay contacts so neither carries the full current. I prefer the latter, but functionally, there is no difference.
There are others, but none important here.
Relays and fuses are there to protect the wiring, and thus, the vehicle. Poor wiring can be disastrous.
_______________________________________ Current: 2002 9-5 Aero Kombi Cosmic Blue 2000 9-5 SE sedan, Imola Red 1990 900S Rose Quartz, Auto Past: 1999 9-5 LPT Combi 1999 9-5 LPT sedan 2002 9-5 Arc 1990 900 5-speed 1986 900 turbo Convertible 1991 9000 turbo 1980 99 GLi 1986 900 turbo 1986 900 S 1991 900 turbo 1984 900 turbo 1976 99 GL
, Thu, 11 Jun 2009 12:33:09, Thu, 11 Jun 2009 12:22:09
, Thu, 11 Jun 2009 17:06:11, Fri, 12 Jun 2009 10:42:21 <-- Viewing This Message, Fri, 12 Jun 2009 12:12:53, Fri, 12 Jun 2009 08:20:43, Fri, 12 Jun 2009 09:16:22, Thu, 11 Jun 2009 17:04:42
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