Classic Retro AC question

[SpyderMike]

Nearing the end of my hybrid install and I have a Q regarding the orange blower sense wire. I am not using their blower but the Griffiths Hurricane. Is the Orange sense wire just looking for 12vdc when the evap blower is on or it is sensing blower speed? I emailed CR, but they are closed until the 8th. I am hoping to finish before then.

[Nditiz1]

From the text

"You do not have to install our cabin button. You can use the factory blower switch to turn on the
AC. This requires wiring the orange wire in our loom to the red/white wire on the factory blower 4
pin connector"

So you will need to wire accordingly.
I will be working on this setup soon as well. Would love to read your results. My hope is that the hybrid approach will be just what is needed to push the maximum cold air into the car.

[SpyderMike]

Mine is a hybrid system and the original cabin controls and AC wiring are gone. I am installing a PWM with rheostat to control the evap blower speed...I will try to figure out what the red/white wire did on the original system.

[Nditiz1]

OK, so you are not going to use the original blower at all. In that case you will need to send power to that orange wire letting the compressor know that the blower is "on." I assume it is just 12v going to it. If I can get to my orange wire, I will check the voltage with the blower on.

[SpyderMike]

The red/white wire appears to be the power wire to the evap blower from what I can tell, so it sees different voltages? Will you please measure it at the different speeds? I appreciate the help!

[Nditiz1]

Here are the stats
Blower off - ~12v
Setting 1 - ~7
Setting 2 - ~3.2
Setting 3 - ~.6

The car was not running with these tests. I'm not sure if the CR ecu needs these numbers to understand to turn on or not. I would assume it is setup to see how it compares to the battery voltage OR if orange wire is 10 volts or less, power on compressor.

[SpyderMike]

Thank you very much!!

Good point - not sure if the ECU needs to know the varied voltages and how this would be affected by a PWM. I might have to wait for CR to get back from the break.

[wazzz]

Originally Posted by Nditiz1

Here are the stats
Blower off - ~12v
Setting 1 - ~7
Setting 2 - ~3.2
Setting 3 - ~.6

The car was not running with these tests. I'm not sure if the CR ecu needs these numbers to understand to turn on or not. I would assume it is setup to see how it compares to the battery voltage OR if orange wire is 10 volts or less, power on compressor.

The CR ECU would probably not care about which setting (1, 2, or 3) is used, but simply turn on when it sees power (+12V) on the green/white wire running from the AC blower switch. Have a look at the air conditioning and heating diagram in the Bentley.

[SpyderMike]

I have Wazzz....and CR show using the red/white wire which is the wire from the resistor pack to the evap blower motor...with varied voltages depending on switch setting. Maybe they do this because it is a simple single connection and not three?

Looking at their setup manual, there is a diagnostics output reading named "Blower Speed State", but in the setup menu the only set point/condition I see is called "Blower On Sense Voltage" and their initial set point is "< 7.0V".

They also state - "The blower fan MUST be running for the A/C to switch on. Electrocooler detects the fan voltage using the orange wire on the side of the blower."

Based on the above and Nditiz1's readings, I am coming to the conclusion that the red/white wire shows that the blower is on at around 7.0Vs or less. If the PWM doesn't trip the system at this <7.0V set point, I might need a resistor in the sense line to bring 12V to below 7V or change the set point in the software to trigger properly.

We will see...

[Nditiz1]

I think you are on the right track Mike

[Jonny H]

The ECU senses the voltage on the orange wire and uses a threshold to determine whether the blower is on. Because some blowers switch the 12V (high side switching) and others switch the GND (low side switching), the threshold is either > V or < V depending on the wiring.

The threshold is set using the BLV command. Less than thresholds are entered with - numbers, e.g. entering BLV=-9 means < 9v. Positive thresholds are entered with BLV=4 ( meaning >4V). You can check the voltage on the blower orange wire by typing DIAG and looking at the value for BLO as you change blower speeds. You want it so that the ECU correctly reports Blower On for all speeds except Off.

Low Side Switching
============

On a standard 911, the fresh air fan sliders switch the GND. As the blower speed gets higher, the orange wire gets nearer GND (0V).

You'd expect to see something like :

12V Off
8V Speed 1
4V Speed 2
0V Speed 3

Thus the default setting for BLV=-9 (meaning <9V) for 'Blower On'

High Side Switching
============

Being a Porsche, things are never easy and guess what? The AC fan blower (original smuggler's box install) is wired the other way (rotory switch supplies 12V)

You'd expect to see something like :

0V Off
6V Speed 1
9V Speed 2
12V Speed 3

Thus the setting for using this would be something like for BLV=4 (meaning >4V) for 'Blower On'


So, in summary use DIAG to view the voltages and set the threshold using BLV. adjust so that the Blower On/Off is correctly reported for all fan speeds. Note that the voltages may change with the car started so do this with the car running.

It's important to get this right since the compressor will not start if the ECU thinks the blower is off.


See point 3:

https://classic-retrofit.com/forum/index.php?/topic/1006-what-to-do-if-your-ac-compressor-wont-start/#comment-1550

[SpyderMike]

Thank you for this reply! My system should work then with the sense wire on the output of the PWM controller. Sweet!

Can you tell me why the main power to fans and ECU are not run off ignition switched power?

[Jonny H]

Originally Posted by SpyderMike

Thank you for this reply! My system should work then with the sense wire on the output of the PWM controller. Sweet!

Can you tell me why the main power to fans and ECU are not run off ignition switched power?

Fans - too much extra load for the ignition switch.

ECU is through ignition (yellow/black, yellow) - only 100mA or so.

[SpyderMike]

Got it, thank you! So I have a custom electrical system that removes all large loads from the ignition switch. I have the system running off a main electric contactor. This tells me I am okay with my wiring scheme.