I believe that daytime running lights improve your visability and probably
can help avoid accidents, so I leave the lights on all the time.

Now I woke up to the drag on the electrical system and was surprised.
A pair of 55 Watt low beam bulbs and four 29.5W parking lamp bulbs equals
16 Amps. Then there's other current draw with dash lamps, relay coils,
and other bulbs so the grand total is more.

My multimeter will only measure up to 10 Amps, so I better not try to measure
the headlight circuit current. Does anyone know what the current draw is?

The bad news is that the alternator charging away at <16 Amps all the time
is providing unwanted drag on the engine and lowering fuel economy.

The good news is that there are LED replacements for many of the bulbs
that use a fraction of the current.

for example the #1156 bulb is rated at 27 watts or it draws 2.0 amps
and an LED replacement draws only 140 ma or 0.14 Amps

There's some websites where people seaching for fuel economy unhooked the
alternator and made sume jury rig to run the waterpump and they found maybe
10% increase fuel economy/ MPG . That idea isn't great for an 850 that needs
fuel injectors and electric fuel pumps and a computer.

I'd like to have daytime running lights without the high current draw of all
the old incandescent bulbs, and wonder what it will mean to gas mileage.

Then there's the expense of LED replacements:
Here's the first place that I found that has a nice website and lots of options:
http://www.superbrightleds.com/
You can look up a variety of cars , and they seem to have it right.
They have daytime running light replacements, (That must go into my non-existant
fog light sockets) but NO HEADLIGHT replacements.

I was told that there are now aircraft LED landing lights, so perhaps someone
has a headlight replacement for the Volvo 850 now?

Comments?

Bill

Some of the 240 guys have replaced tail light and front parking lights with home made LED boards. Headlights are in the not too distant future, I hope.

BTW, the alternator should be putting out around 14.5V at the battery connetion. Enough to fry all of the lightbulbs that are rated at 12V.

Hi Klaus,

Hopefully the voltage regulator limits volts to about 14, and yes
filament bulbs go away faster with increased voltage.
The LED lights I've been looking at run from 10-30VDC so they are
not messed up so easily, and the rated life of SMD devices is 10,000-
30,000 hours, so expect to see everything switched to LEDs soon.
(Check out the scary filament bulb prices at Autozone, if you think LED
replacements are priced crazy)

I found four tail light bulbs instead of two, so add another 4 Amps of alternator drag to my previous estimate.

I found a lot of choices for replacement LED's that include different color, brightness, narrow or wide angle output, and of course cost.
I haven't found headlight replacement modules yet.

What does it cost in MPG and engine performance, to run AC?

Bill

While the compressor is engaged, expect to suck up 1-2 mpg. Fortunately, Volvo does cycle the compressor to increase mpg compared to American/Japanese systems. My MB does not cycle, it is either off or on, and I can watch the mpg go down by 2 when the AC is switched on. Stupid car has an American system and the climate control is really DUMB and slow to react to temperature changes. Volvo is so much better!!

Go to the RWD section and search for LED...