After reading Dan Stern's page on lighting I got to wondering if putting relays in would help the anemic lighting on my '88 240. The lenses are fairly clear, better than 90% of the cars I see running around here, and the Sylvania Extra Vision bulbs made quite a nice difference but the lights still weren't great. What I was curious about was the voltage.
Dan's page has information from Hella that states:
13.5V puts out 100% of the designed output of halogen lamps.
12.8V puts out 83%
12.5V puts out 67%
11.47 puts out 53%
Using a good quality digital meter (Fluke) with a probe stuck into the wires at the lights I tested the voltage under load, by turning on the car and putting the low, then high beams on. I came up with the following readings with the stock wiring and the Extra Vision lamps.
Cold alternator (just started)
At the alternator -------------------------- = 14.18V
At the connector for the low beam = 13.05V
At the connector for the High beam = 13.01V
Hot alternator (1/2 hour drive @ 80F)
At the alternator --------------------------- = 13.70V
At the connector for the low beam = 12.52V
At the connector for the high beam = 12.25V
As you can see I was loosing over one volt and was only getting about 65-70% out of my lights as soon as the car warmed up. After completing the installation of the relays I took another reading.
After installing relays, car and alternator still quite warm.
At the alternator --------------------------- = 13.91V
At the connector for the low beam = 13.78V (both sides)
At the connector for the high beam = 13.60V (both sides)
A large difference with minimal voltage drop, the proof however is in the night driving. There is a large difference, not like the set of H-1s I stuck in the turbo, the beam pattern still leaves a lot to be desired but visibility is WAY up from the old stock lamps and a lot brighter than the Xtra Vision bulbs were with the stock wires. My evaluation is DO IT.
I am also thinking about finding some way to cool the alternator without subjecting it to road dirt and water, there is too much drop as it gets hot.
Pics of the job and a brief how to are here
This made a heck of a difference but the Glass Euro Lights were the final ticket
