[justpushplay]

I would like for my fans.....to use their normal routines.....but to shut.....off when normal air flow is established. I like the idea that they aren't running full time at highway speeds. 
 
Do I need to add a speed sensor (VSS)?

And...... people in hell would like ice water! I'm electronically challenged, but I have a brain, so I'm fairly confident that the computer can't possibly know when "normal airflow is established" without extrapolating info from a vehicle speed sensor (VSS) at some particular threshold, OR from the signal of an airflow sensor (anemometer or MAF?) at the threshold of some predetermined flow rate. 

I wuz wrong once B4 and (as said) I'm electronically challenged ~ BUT...... that sounds to me like a fairly-involved programming task for the average car enthusiast (AI needed?). I think I would be more inclined to let the fans run continuously with the A/C on, regardless of speed/airflow ~ OR, as the OEMs do, use a combination of coolant-temp sensing and A/C system-pressure sensing to determine the need for fan operation. <shrug>

Poorly written on my part. By 'normal air flow' I meant 40 mph which is what I understand to be the EEC fan cutoff speed. Even that could be wrong, I'm looking for that answer.

[dan_xr4]

The LA3 strategy is not calibrated to turn off the Low Speed Fan or the High Speed Fan based on vehicle speed. The strategy checks vehicle speed on pins 3 (VSS+) and 6 (VSS-) but the vehicle speed is currently set to 127.5 MPH. Only the Low Speed Fan is checked and the High Speed Fan does not have a vehicle speed check. The Low Speed fan will always stay on for coolant temperature at any vehicle speed. The Low Speed fan will only turn off at high vehicle speed when air conditioning is the only reason for the Low Speed Fan being on.

[justpushplay]

I would like for my fans.....to use their normal routines.....but to shut.....off when normal air flow is established. I like the idea that they aren't running full time at highway speeds. 
 
Do I need to add a speed sensor (VSS)?

And...... people in hell would like ice water! I'm electronically challenged, but I have a brain, so I'm fairly confident that the computer can't possibly know when "normal airflow is established" without extrapolating info from a vehicle speed sensor (VSS) at some particular threshold, OR from the signal of an airflow sensor (anemometer or MAF?) at the threshold of some predetermined flow rate. 

I wuz wrong once B4 and (as said) I'm electronically challenged ~ BUT...... that sounds to me like a fairly-involved programming task for the average car enthusiast (AI needed?). I think I would be more inclined to let the fans run continuously with the A/C on, regardless of speed/airflow ~ OR, as the OEMs do, use a combination of coolant-temp sensing and A/C system-pressure sensing to determine the need for fan operation. <shrug>

Poorly written on my part. By 'normal air flow' I meant 40 mph which is what I understand to be the EEC fan cutoff speed. Even that could be wrong, I'm looking for that answer.

The LA3 strategy is not calibrated to turn off the Low Speed Fan or the High Speed Fan based on vehicle speed. The strategy checks vehicle speed on pins 3 (VSS+) and 6 (VSS-) but the vehicle speed is currently set to 127.5 MPH. Only the Low Speed Fan is checked and the High Speed Fan does not have a vehicle speed check. The Low Speed fan will always stay on for coolant temperature at any vehicle speed. The Low Speed fan will only turn off at high vehicle speed when air conditioning is the only reason for the Low Speed Fan being on.

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The LA3 strategy is not calibrated to turn off the Low Speed Fan or the High Speed Fan based on vehicle speed. The strategy checks vehicle speed on pins 3 (VSS+) and 6 (VSS-) but the vehicle speed is currently set to 127.5 MPH. Only the Low Speed Fan is checked and the High Speed Fan does not have a vehicle speed check. The Low Speed fan will always stay on for coolant temperature at any vehicle speed. The Low Speed fan will only turn off at high vehicle speed when air conditioning is the only reason for the Low Speed Fan being on.

Now that the LA2 is installed in my '85 XR 5 speed, my fan routines have been exactly the same as they were with the stock PF2. It just works. The only anomaly has been with the angry-bee green #3 WOT relay. That has been corrected for now, with a simple jumper, and will be corrected with a modified relay in time.

dan_xr4
"The LA3 strategy is not calibrated to turn off the Low Speed Fan or the High Speed Fan based on vehicle speed."

My understanding is the LA2-3 uses a speed threshold to 'disable' the engine 'puller' fan(s) at a predetermined speed, as informed by the T5/auto trans mounted VSS. If either of the fans have been called on to run by temps/pressures, then that would supersede any speed related 'fan off' call.

"The strategy checks vehicle speed on pins 3 (VSS+) and 6 (VSS-) but the vehicle speed is currently set to 127.5 MPH."

Explanation please? I have pinned/wired my LA2 to take advantage of the VSS function. I have installed the speedo mounted VSS, but a speedometer cable mismatch with this particular VSS renders that moot for this discussion. Let's just assume that it is fully functional for now and 8 pulses per rev/8k pulses per mile will keep the LA2 happy.

Is this saying that 127.5 mph is the default base value the LA2 invokes when there is no data present on pins 3 and 6? This is the first I've seen that number referenced.

"Only the Low Speed Fan is checked and the High Speed Fan does not have a vehicle speed check."

I am taking that as the condenser (pusher) fan will kick on with a pressure/temp call, regardless of vehicle speed. I like/want this behavior. I want the normal over temp/pressure fan routines to always supersede the speed related shutofff call.

"The Low Speed fan will always stay on for coolant temperature at any vehicle speed."
I am reading that as 'stay on for high/over coolant temperatures at any speed'.

"The Low Speed fan will only turn off at high vehicle speed when air conditioning is the only reason for the Low Speed Fan being on."

Again, this is precisely what I want to happen. I see no reason to be running my pair of engine puller fans while at a speed that produces better airflow than the fans can provide.

Assuming assumption is the Mother of All Fuckups, I just wanted to be clear with my assumptions:-) And that is that, with no other changes, and the XR/LA2 is getting the data it wants to see from a VSS, my XR will do exactly what I want it to do regarding it's fan routines. Is that a proper assumption?

Thanks in advance for any feedback. And sorry for the intrusion of a clueless XR owner cluttering up this space. So much great info, and people, here.

[dan_xr4]

Yes, the LA3 has a vehicle speed threshold to disable the low speed puller fan in the Turbocoupe. The vehicle speed is determined by the T5 manual transmission / A4LD automatic transmission mounted Vehicle Speed Sensor. The vehicle speed threshold is set to 127.5 MPH. Whenever your vehicle speed is over 127.5 MPH, then the low speed fan can be disabled.

The LA3 strategy was designed to be able use a vehicle speed of 40 MPH to disable the low speed fan, but unfortunately the calibration of the LA3 strategy does not enable the use of vehicle speed because it is calibrated to 127.5 MPH instead of 40 MPH.

If the low speed fan has not cooled the engine, then the high speed fan will turn on. As long as the high speed fan is on, vehicle speed will not disable either the low speed fan or the high speed fan.

With no data present on pins 3 (VSS+) and 6 (VSS-), the computer should read vehicle speed to be 0 MPH.

You have two puller fans and a pusher fan in your XR4Ti ? I don't think you want to connect the pusher fan on the XR4Ti to the high speed fan in the LA3 computer. The high speed fan on the LA3 mostly only runs when the coolant is over 220F.

The Air Conditioner only effects the low speed fan in the LA3. The Air Conditioner has no effect on the high speed fan in the LA3.

In the XR4Ti the puller and pusher fans are controlled by the vehicle not the computer. Changing computers in the XR4Ti does not mean you need to change how the XR4Ti puller and pusher fans are controlled.

No, you cannot get your XR4Ti puller or pusher fan to turn off above 40 MPH using the LA3 computer. The LA3 computer can turn off the low speed fan, if the engine temperature is below 190F and the vehicle speed is above 127.5 MPH.