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When using our small ECU in custom applications we often get asked about the orange wire in the loom and how/why it connects to the cabin blower. The orange wire is used to 'sense' if the cabin blower is on. Primarily this is used to stop the compressor from running if the blower is switched off. This prevents the evaporator from freezing due to lack of airflow. Simple enough.... There are, however, many different cabin blower fans ( e.g. fixed speed, multiple speed, variable speed etc). Additionally, some blower motors are wired as 'high side switching' and some as 'low side switching' High Side Switching In a high side switching system the motor negative is connected to chassis and 12V is applied to the motor positive through a switch. The orange wire should be connected to the positive side of the motor and the ECU needs to be set to detect a voltage threshold above a certain voltage to mean 'ON'. This is done using the BLV command in the ECU and the usual recommendation is anything above 4V should mean 'ON'. This allows for blowers with resistor packs where the slow speed usually runs about 6 volts. To enter this setting in the ECU, type BLV=4 <enter> e.g Blower Voltage > 4V means ON. Low Side Switching In a low side switching system the motor positive is connected to 12V. Motor negative is connected to ground through a switch. The orange wire should be connected to the negative side of the motor and the ECU needs to be set to detect a voltage threshold below a certain voltage to mean 'ON'. This is done using the BLV command in the ECU and the usual recommendation is anything below 9V should mean 'ON'. Note that on a low side blower the voltage will reduce closer to 0V as the blower speed increases To enter this setting in the ECU, type BLV=-9 <enter> (note minus sign) e.g Blower Voltage < 9V means ON. You can check the blower voltage in real time using the DIAG facility in the ECU to test your actual voltages and set accordingly. Automatic Compressor On with Blower Some simply installs want to minimise the amount of controls. After the above thresholds have been set, you can also enable another mode If you want the compressor to start automatically when the blower is switched on. Change the input button mode (BUT) to blower operation.

Yes, old school mechanical compressors use around 4HP and are 'cycled' using a clutch. ON, OFF, ON, etc Our electric pump uses around 80A @ 12V ( about 1000W ) input power. The output power, however, is higher since the COP (Coefficient of Performance) means its cooling capacity is around 3000W. Now, if the clutch based mechanical compressor is cycling on a 50% on, 50% off basis, it is only actual providing 50% of the stated the cooling power. The electric compressor runs all the time so it's cooling power is not reduced. On balance, the electric compressor does have LESS power, but a clutch based mechanical compressor is somewhat misrepresented in its specification. The electric compressor will never be as powerful as a mechanical one, but we compensate by specifying high grade modern highly efficient components for the other parts of the system. Our focus is on small cabin sports cars that want a lightweight and discreet system.

Will the new heat pump system still require a 175 AMP Alternator?

Hi there! I have a replika that needs some cool air. I was talking to an auto shop here and they recommended installing a proper system, but I am unsure. Apparently, in a modern automobile, the A/C system will use around 4 horsepower (3.0 kW) of the engine's power, thus increasing fuel consumption of the vehicle. If you consider an electric system that runs on 12V, this would roughly be equal to 250 amps. This unit which is purely electric uses less than 1 horsepower – therefore also only ¼ of the cooling power. Is that correct or am I missing something? I mean surely your system works right? Attached an image of the engine bay. The red circle indicates the space where I can mount a traditional compressor, or the electric kit that you offer. There is also enough space for a larger electric alternator. That can be accessed really easily. I really want to understand how this will all work here before continuing. Please let me know!

have you check the wiring? back to basic?😀

Andy Hi Jonny. The Singapore car that I spoke to you about 10 days ago or so, when the ignition is switched on, after a short delay the compressor and condensor fan start running and won't stop until the ignition is switched off. The button has no control of the aircon, even though when you operate the button the brightness changes. If you remember I was unable to access the diagnostics at one stage and to make the system work I had to bypass the main contactor, even though I had replaced it with a 200 amp relay of the same type as original. What do you think the problem could be? Kind Regards.

Good morning. We would advise having the system re-gassed by an air conditioning service centre. Systems can lose pressure over time. A second condenser will greatly improve performance.

Hi! I own a carrera 3.2 from 1986 fitted with the single condenser version of the AC. In hot days (hot...not eaven the worst summer days) it does not do the job....it still gets hot inside. I am from argentina we have lots of 30+ degree days.... I just got the car...i reviewed the way the AC is installed and it seems to be just like your manuals say. How can i be certain the AC is working propperly? Can I add the second condenser to my current system? will that make the air colder? thanks Juan

I got it working after putting the jack end back together. i think a connection was grounding out previously. Now it connects.

I tested the end of the Jack. tip- no continuity sleeve 1- green and orange continuity sleeve 3- yellow continuity and black but only in some positions sleeve 4- black continuity and yellow but only in some positions. When the harness cover is threaded on there is no continuity between sleeves. when plugged in there is 3.3v between sleeve 4 and 2 and sleeve 4 and 3. Is this correct?

I’ll add that I tested 12v constant and ignition and ground at the connector pins and they all check out.

Just finished installing a 400v ac compressor. I already use Putty for another controller so I have the program already. I plugged in the usb and shows up as com10 in device manager I tried opening putty with the parameters in the manual and tried to flash a software update and enter putty through the update. The software update gave a connectivity error message in the DOS screen and putty gives a blank screen i continuity tested the wiring at the end of the headphone jack. Two wires go to the middle pin, one to another pin, one to ground. All of the different shaft separations on the plug have mega ohms between them. when I plug in the usb cable it flashes an led and then goes off. It stays connected in the device manager. Is there a diagram for the end of the headphone jack cable to make sure the wires and going to where they should be? what else can I check?

https://imgur.com/a/porsche-belly-pan-fitting-mismatch-S4JpBpG I ordered and received the belly pan fittings to run an extra condenser for my 77' 911. the condenser threads on the unit I have are 15mm and 18 mm(see pics). The fittings both fit on 15mm. Do I have an aftermarket condenser with a different fitting(non standard)? Does classic retrofit offer an 18mm adapter(that I should have received), or does anyone know where I can get one?

Hi Jonny, Very cool that you keep working on improving the CR AC system, I'm excited about the new generation with heat! The best part for me is that it removes a bunch of weight, parts and complexity from the rear of the car, and lets you using cheaper oversized headers, without the system gaining significant weight vs. just the electric AC. I have a few questions: - I have seen that the new compressor goes in the front now, even for LHD cars. Does it take up more room towards the front of the car than the old battery did? We are in the process of adding an RSR style oil cooler duct to the nose of one of the cars we are building, so I am wondering if this could interfere where it protrudes inside the frunk. - Does the smuggler's box stay completely empty now? This would give us room for adding electric power steering, which in my experience is very nice for parking in town with wide tires and lets you run more camber, while not interfering at all at faster than walking speeds. - Will the new system come with a battery mount? From the video and pictures it looks like you are using a Odyssey 680 or 925. Cheers, Lukas

Hi TB, Just closing out on this. I dug into the operation of the alternator and figured that the black connection was feedback from the external regulator. I was worried that I might fry the alternator if I did some incorrect connections. I also checked that the external regulator was disconnected, and it was. I put the green wire on the right connector and left the black wire off (insulated). And when I put the Alternator back in the charge light worked correctly. So I’m not sure what the guy who installed the alternator was thinking. Thank you for your guidance. Regards, James

Thanks Jonny, that means i have to remove the AC suitcase again just to test the sensor.😅😅😅 I was hope to minimize the work to solve the issue. Btw, what is the price if I order an additional temperature sensor harness from you with longer harness from you? Thanks and happy new year.

It cannot. Your clicking is most likely caused by the spoiler gearbox case splitting open, allowing the gear to ‘hop’ a tooth. You really can’t glue the old gearbox case back together, hence why we make this kit.

KBET is a correction constant used for linearisation of NTC thermistors. NTC thermistors are non linear, meaning that their resistance vs temperature graph is a curve. The standard ‘correction’ uses a formula which is coded into our software, leaving the beta value configurable so we can use different sensors. More info in the article below: https://product.tdk.com/system/files/dam/doc/product/sensor/ntc/ntc_element/general_tech_info/ntc_thermistor_general_technical_information_digest_en.pdf In the case of the evap sensor, place it in Ice water and adjust the KBET value up or down by increments of 10 until the temp reads 0 degrees. Note that you must type SAVE after changing KBET for the value to be remembered after power off.

I saw the post regarding a power feed for the Turbo fuel pump fuse position (position 16). In my 79 930, there are already two wires feeding into Terminal 17 (A-Side) and it seems to be a pretty tight fit, so I am unsure I can get the Connecting Rail installed. The other complicating factor is that the gap between the two terminals may be slightly wider than the Connecting Rail supplied from Porsche. Would you suggest pulling a power source from Terminal 15 instead? Appreciate your suggestions here. Thanks. Toby Pennycuff

Hello, Thanks for taking the time on answering me. Appreciate it! So i looked for a better mechanic that was familiar with P-cars and CIS overrall. We went back to basics, installed the old WUR that was working with the car when i got it, checked for vaccum leaks, tested the fuel pressure (still showing some issues with the Cold pressure with the old WUR) and basically the Dizzy was incorrectly installed and by moving a couple of tooths, cylinder 1 was not responding, basically death, so he re index the dizzy, checked the "hall effect sensor" and lubricated the dizzy and installed as neeeded (TDC on Z1) everything as per the manual, and the Car fired up and run as smooth as before... so the CDI+ WAS NOT THE ISSUE as the first mechanic stated it was how he setup the distributor. As an FYI, the hardware eas OK it was basically a mess up from the first mechanic. So the new mechanic, setup the car for me to test it for a couple of weeks (basically for christmas and new years eve time), so far so good, feels really good as before... as soon as he comes back from winter break, we are going to install fresh plugs, install the new WUR (check for pressures) , install the SSI´s, wideband sensor and will be starting to tune it a little bit and playing with the setup, timing and so. thanks again!

Thanks Jonny, Currently KBET is 3950 as default value. Can you explain more about this value? Do you have any related link to explain this? What is the KBET value suitable in my case?

Since the main task of the sensor is to prevent freeze, yes you can adjust the KBET value so that the sensor is accurate about the freeze point (0 deg C). Set the ETC value a couple of degrees higher.

Thanks What about if I don't replace the sensor and use the temperature reading difference as a constant to correct the reading for ECU? Thanks

May I ask: can the 993 air wing travel limits be adjusted? I have replaced the bearing but I occasionally get the dreaded clicking noise when the air wing closes. I appreciate your thoughts. L. Cunningham 1996 993 Carrera

You need a 10K. the four wire harness is for two sensors. The sensors are not polarised. You should see how they pair simply by looking at the plug.