DIYbanter - View Single Post - Ford car stereo F87F-18C815-BB drains car battery.

David Farber

wrote:
David Farber wrote:
I was given this Ford F87F-18C815-BB factory tuner/cd player to see
why it's draining the car battery to the point where the car won't
start.

This radio appears to be for a late 90s-mid 00s Ford. If the car
still has the factory battery, replace it. If the battery that's in
there now is more than 5 or 6 years old, replace it. You and the car
owner will be happier.

Do I need 12V on pin 3 (start), pin 4 (clock), pin 9 (battery), pin
10 (run:acc)?

My guess: apply power to pin 9 only to simulate the key off position.

Apply power to pins 9 and 10 both to simulate the key on position.

I don't know what pin 3 (start) does, but I suspect it might be for
"load shed" when you turn the ignition key to "start", so the engine
starter gets the maximum possible juice. Some cars do this by having
two different "run" wires from the ignition switch - one gets dumped
in "start" and the other doesn't - but I can see them just using the
"start" wire as a disable as well.

Is the "clock" the actual time of day display or is it the internal
clock for the system processor(s)?

"Clock" is probably either a constant +12 V to keep the clock running,
or maybe it has to do with when the clock is displayed. (Like, maybe
the body computer sends 12 V to it when you open the door, so the
clock comes on with the dome light.) If it's constant 12 V, then I
don't know why it doesn't just use pin 9, but maybe they wanted to put
it on a different circuit.

Are pins 1 and 2 (illum +/-) just the 12V input that power whatever
accessory lights there are?

Probably.

Can that be jumpered to the 12V line as well? Is it ok to common
ground the illum - pin to pin 11 (radio gnd)?

In the car, they may get fed from a rheostat or PWM box so as to have
something less than 12 V on them. You might apply something like 6 to
8 V DC to pins 1 and 2, only, and see if the display or buttons start
to light up. If that looks good, then ramp up to 12 V. If 12 V looks
good, then yeah, you can just connect pin 2 (illum -) to pin 11 (radio
ground) and pin 1 (illum +) to either pin 9 or pin 10. If 6 or 8 V DC
makes the display or buttons light up insanely bright, then go down on
the voltage a little.

Also, does anyone know where to get a schematic for this unit?

It probably exists on two hard drives at Ford (or their supplier) and
nowhere else. A few repair places, like the one you linked, may have
one, but they probably want to repair your stereo for you rather than
give (or sell) you a copy of the schematic. I wouldn't hold my breath
waiting for one.

Matt Roberds

Hi Matt,

I powered up the unit with by putting 12V to pins 9 and 10. With the unit
powered on and no load or signal, the draw was about 545ma. In standby mode,
the current draw was about 4.5ma. I was checking the illum terminals and
decided not to put 12V to illum + and ground because illum - terminal was
not grounded. However I did put an ohmmeter across the + and - illum
terminals and it was 4.2 ohms. There are 12 lamps on the display board. They
are not in parallel.

I'm going to reinstall the radio tomorrow and see how these numbers compare
to the current drain from the car battery.

Thanks for your reply.
--
David Farber
Los Osos, CA