On my 99 I just installed a 34 inch two row core radiator and 07+ fans with a Black Bear harness yesturday and I like them but the control isn't working quite right. I bench tested the harness plugged into the fan motors of course before putting them on and and IIRC grounding the green wire turned both fans on in series (low speed) and grounding blue and green both turned both fans on in parallel (high speed) as it should. I could have my colors mixed around, going off memory here, but none the less low was low and high was high and that part worked great. So I got them on and started the truck and turned the AC on and using known good AC gauges the high side got up to 350 psi before the low speed fans turned on. I was never able to get a high speed on vs psi reading because as soon as the fans turned on low the high side dropped like a rock and they turned off not too long after that. The fans move an insane amount of air even on low. Now based on temperature the fans turned on at what I'm going to say is 190 degrees. My temp gauge is very accurate and low speed turned on just before the needle reached the operating temp of 195 so I'm going to call it 190 when the low fans came on. I went and drove it and when I got back high speed fans kicked on at 35 mph (correct speed) but it was only at 195 degrees and I know the AC pressure was nowhere near high enough to need the high fans. Basically it seems like there is a calculation issue wrong somewhere or maybe efi live was in say kpa or celcius or something when the values were inputted. This is the only way I could see this happening unless someone else knows whats going on. Sorry for the long read but I'm going back for a retune saturday and want to get this right. Attached is what I used for fan settings only low speed on was meant to be 205 and off at 200 and high speed on at 210 and off at 205 on my application. Can anyone shed some light on what might be going on? IIRC stock fan on temps were very high like 230+ for low speed and I've never known them to get anywhere near that high stock for engine cooling. This leads me to think the calculations within the PCM is off somewhere and they just through whatever values in to make the fans operate correctly regardless of whether the values seemed logical or not.



Here is the final product. Need to lengthen the ground and move it to a spot on the front of the head but otherwise it turned out very nice.

 

Nice install

 

I know. This is my daily driver and I wanted/had to have stock appearing and functioning fans. I've got the appearance just don't have the functioning quite yet. It was a little more cost up front but I figure 11 years old 152k those plastic radiator tanks won't last forever so its preventative maintenance replacing the radiator now as well as nearly doubling the cooling capacity.

 

I am having problems with mine as well normal driving ac off mine run both on low but kick on the ac and only one runs and on high. But my ac psi is higher then yours are set so maybe that's why? Very nice intall by the way.

 

on the 99 pcm/ecm i thought there was no provisions in the ecm to control the fans.
am i wrong?
the pin outs are there for the blue and green wires but nothing there in the ECM.
thanks
Ed

 

The controls are there for the fans. The problem is, there is no variable a/c pressure sensor. It's just a switch the closes at ~425 psi.

 

well then couldn't you just run a toggle switch for the speed fan when the a/c is in use then?

 

Like the other guy said, there is no PCM A/C pressure sensor on the 99-02s. I set mine to where they always run on low below 35mph so air is moving through the condenser.

 

I'm not sure I believe that. With the AC on my fans will come on low at around 350 psi and go off around 200 psi. Something is inputting to the PCM that the pressure has gotten high enough to turn the fans on and then to turn them back off when the pressure dropped.

I did get it reflashed and have the fans operating based on temp correctly but I haven't yet put the gauges on it to see what its doing based on pressure. I do know that say driving around town at 20-30 mph with the AC on the fans are almost always on low as they should be. You guys may be right about there not being a 3 wire variable pressure sensor but something is damn sure telling the PCM a pressure reading and its not the AC high pressure cut out switch or the low pressure cycling switch.

 

Reread my post.