An EXCELLENT GUIDE
Warning: USE AT YOUR OWN RISK! FIT AND FUNCTION ARE NOT GUARANTEED! NO WARRANTY, EXPRESS OR IMPLIED, IS PROVIDED FOR THIS MODIFICATION! This is working OK for me, but we'll see what the Texas heat brings next summer.
Goal: replace gen I hydraulic fan system with the gen II electric. Want to keep the intelligent fan control functional. Yes, this can be done cheaper with aftermarket fans, but the controls are typically lacking. This integration allows the
PCM to select the fan speed from very slow to very fast depending on conditions. You can also get to my full flickr feed of LS mechanical work w/ high res copies of the pics. No pretty pictures, sorry.
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Stuff you need:
Gen II fan and wiring pigtails: note that 03/04 has two connectors while 05/06 has one. Wiring, colors and everything else is identical.
Alternator (possibly)
two sets of two pin weatherproof connectors
6 gauge wire, ring and butt connectors
18(ish) gauge wire and various connectors
Provisions for control mechanism of your choice (see below)
Electric fan basics:
The power and ground should be connected at all times. No relays or switches. Get a 60
amp fuse. The fan pulls 43 amps at full blast.
Big red and big black wires are obvious. The small green wire feeds power to the in-fan computer and is on in run and start for the stock install.. The white/black wire is the signal line that carries a PWM that instructs the fan on what speed to run. The really nice thing is that if the fan computer can't figure out the signal, it'll fail-safe to full speed. The signal line can be grounded, hot, floating, whatever, without damaging the fan. So if all else fails, just run the sucker full blast. Fan will only run when power is applied to the computer. Although, if it's bootstrapped, then power removed with the signal still connected, it can sometimes remain running. My initial install just left the signal wire floating. That is not a very good choice, however.
Other fun notes: fan pushes a significant ripple into the car's power rail when running full blast. Looked like about 1V @ 2khz (ish). Audio dudes beware.
Power:
If you have a bunch of accessories/options, then you'll need a stronger
alternator. The stock is barely adequate for the car with all options. Big stereo? Get an
alternator. Seat heaters? Get an
alternator. My car does not have the heaters and only the stock
radio, no other gadgets.
Removal:
Remove old fan and hydraulic pump. Remove all hoses. Plug cooler inlet/outlet. I had to drop the
a/c condenser to get to the outlet on the cooler. That took an hour alone. You do not need to disconnect the
a/c drier, although you may need to loosen various hose mounts to get enough movement.
Connector and
alternator:
While
alternator is off, cut off the old actuator connector and add your own two pin connector. I did this after everything was back on, and it's REALLY hard to solder between the engine and the frame. Keep track of which pin is which. Green is power, Brown is signal.
Install
alternator and new belt. My belt was 100 1/4" Gates - normal stock
part at my local store.
Fan modification and installation:
See hydraulic fan vs electric Front:
Back:
Note that the hyd blades are much larger. This means it can spin slower to move the same amount of air, but is harder to turn. So the electric will spin faster - and be louder - compared to hyd. Electric does not have
water pump mounts, but that's OK.
A/C drier mounts just fine.
**ALL PROTRUSIONS ON THE PASSENGER SIDE MUST BE GROUND OFF!** Not the mounting tabs - the stuff for things to mount to the shroud. Anything that sticks out towards the engine. We spent a couple of hours trying to wedge it in there in various conditions, finally just ground down everything. For the Gen II, the
DCCV actually mounts on the shroud. All that crap just bumps into things.
Make sure to get the tabs into the slots on the
radiator. This is also much easier with the upper rad hose disconnected.
I ran the ground to the body bolt under the air box:
Be sure to clean under the washer to make sure it's bare metal. Hit it with a wire brush.
I pulled the positive along the big wire harness in the front. Got a MAXI fuse block from Wal-Mart - after trying three auto sound stores and Best Buy - and a 60
amp fuse:
Routed through existing harness:
Tied it into the big lug on the fuse panel:
I used 6 ga for the power lines to match those on the harness. The feed line to the fuse panel is a 4 ga, so it should be fine with this extra load. Again, YMMV. Be careful, monitor it for overload.
Run the signal and fan control power lines along the front and towards your new connector.
Control: The Simple Way
Add the opposite end of your connector type onto the fan wires you just ran. Green to Green, Brown to White. This will give you full fan any time the ignition is in Start or Run. This is an excellent fail-safe. So regardless what else you do, have this as an option in case things go nuts.
Problems: In the cold the engine will have a hard time warming up. This can be very bad for you engine if you do short drives in the cold. Extra power load when not required.
Control: The Slightly Effective, but Stupid Way
Note: THIS IS REALLY STUPID.
I was ill-informed at the time and made this monstrosity:
Tie the
PCM power and signal to 85 and 86 (either way). Also tie
PCM power to 30. Tie Fan power to 87. Put in a diode from
PCM signal to
PCM power to protect the
PCM when the field collapses.
OK, WTF did this just do? I found that when the
PCM requests mid to high power, it can throw a relay. So when it does, you're now powering the electric fan computer, and it'll run full speed.
Problems: This is REALLY STUPID because the relay will chatter as the
PCM changes its control signal. This will kill the relay. The rapid field collapses might fry your computer (although I ran like this for two weeks fine). The relay will die quickly. Mine would stick on. But, for cold mornings, this left the fan off while the engine warmed up. A quick whack to the relay when I stopped the car reset it. Annoying, but quick, easy, cheap, and slightly effective.
Control: The Very Effective, but Difficult Way
Why, just adapt the Gen I signal to the Gen II signal. Easy!
Ha.
Granted, I'm horrible with analog circuits, but I spent around 60 hours getting this to work. At least half of that was just me not being very good at analog work.
Gen I is a PWM, period of 10ms, ranging from 95% duty cycle for minimum speed to 10% duty cycle for maximum speed. The Gen I *switches ground* to make the PWM. Key note. If you hook up a standard
multimeter you'll get some funny results (like a smooth resistance curve, which makes it look like it just changes resistance to ground, which can cause you to spent two weeks designing around that, just to learn that isn't what it's doing at all and getting really mixed up).
The Gen II signal has period 7 ms, ranging from 5% duty for minimum speed to 95% for maximum speed. Note that if you fall under ~5% duty then it'll lose the signal and run full speed.
I built a circuit based on the TI TL494. This can be done with any similar chip, and in lots of other ways.
Schematic:
I used a 50k pot on the voltage divider feeding DTC. It's set around 14k right now. Adjusting that changes when the output curve starts. I didn't get a perfect match (ie, 90% in = 10% out, 50/50, 10/90, etc), but pretty close. Changing this value lets you either delay when the fan engages - and reduce max speed - or engage sooner and get to max speed sooner. It's just a trade. I expect to adjust it again during summer. Upping the voltage divider by an order of magnitude might be a good idea. The PWM output resistor set can be higher - it was stable at 470 ohms, shaky above 600 ohms. The set of four 1k's is about 270 ohms (variance due to 5% resistors). Well within the 1/4 watt rating of the resistors, but may waste a bit more energy than required. The 1k load on the PWM input was also a complete guess. The input filter resistor/cap was determined by experimentation. That set is stable, but there may be better values. The timing resistor is the actual tested value I used. Any variation will change the output PWM frequency. I didn't try to test the timing capacitor for its true value, though. A scope is invaluable in testing.
I got a better curve match when using the feedback input, but that required an op amp voltage follower to buffer the PWM input filter and a different voltage divider. Way more complicated and used quite a bit more power, so ditched that idea.
And a few pics of the final piece. I added some rs232 pins for taps for testing.
I pulled ground from a body bolt on the shock tower then velcro'd the box to the side of the fuse box. Not the cleanest install, but easy to get to. Once I have a few months on it I may hide it under the fuse box.
Shazaam!
This is working so well I may actually do something similar for my '72 Cutlass.
search engine help: fan swap gen 1 I to gen 2 II hydraulic fan replacement
