Thanks That's the route I'll probably go . I'm looking at a INtersil
RFP70N03 70 Amp .01ohm Rds on device and a pair of 555's one for the astable
and one for the PWM
Any recommendations on a better FET?
Bob

"Jamie" wrote in message
...
BoborAnn wrote:
I have a Mercedes E320 that has a blower that only gets to about 30% of
max speed.
I've determined its the blower regulator that takes the control voltage
that varies from approximately 0-8 VDC in 8 steps and controls the ground
connection of the blower ( which has its Hot tied to +12)
The problem is that Mercedes realized that this part ( that cost
$190 )was a bad design and redesigned it for better cooling BUT you need
change the Blower ( another $400+ ) and add a bracket ( another $50) to
use the new one . I've checked all the MB forums and the answer is simply
buy it for $700+
S I opened it up and this regulator is a single 4 terminal device that
has boot over it with the markings 9 140 010 179 Made in France
90.943.02.385
Removing the Boot reveals a device that looks like a high current
rectifier approximately by 1"X1" X1/2: with a metal surface for
attachment to a heatsink ( they use the blower frame for a heatsink.
This device has the markings bk133.1 2fb-5 and I believe its made by Behr
I'd appreciate any help people can offer on what this device might be
I'd like to get a reasonably priced replacement or design a replacement
for it I can send photos ( sorry I have no place to post them)
Also Please no comments on buying this Car my wife always wanted one and
has regretted it since we picked it up
Thanks in Advance
Bob


a simple PWM supply using a Mos Power fet as the driver will do fine.
just a simple variable voltage source via a Pulse width modulator
turning off/on a Power Fet at the correct duty cycle to get the desired
speed you want.
the PWM simply fully saturates the Fet as a switch action at low R when
on. this places the Fet into very low R state and thus will not
heat up. line an analog type variable regulator.
the pulse can be generated via a simple 555 timer etc..


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5