Great, just sent you a PM. Thank you.
You are amazing! Thanks for the tips. The 348 AC ECU voltage is changing the speed indicator. Looks like the ECU is fine. I stabbed the wire from the far side and got an easy read. I must have fried my Fan Speed Controller. Any tips on repairing that piece? Otherwise I'll be digging. Image Unavailable, Please Login
I got the speed controller apart thanks to you. I ordered the TIP142, and should try for the solder job this week. This thread was solid gold. If you are ever in the Pensacola area; I have a beach house rental you can stay at. I'm pretty sure I didn't fry a 8,400 AC ECU, so I'm feeling good. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Hopefully, replacing the two power transistors will fix it. However, the fact that your blower was running at full speed (presumably irrespective of the speed selection at the AC ECU) may mean that there is some damage on the small circuit board inside the controller. Based on the input voltage coming from the AC ECU, the small board will first vary the blower speed via the two power transistors in the range of zero to about 95%. When full blower speed is requested (~ 4.8 volts from the AC ECU), the small board will activate the relay inside the controller which will bridge (bypass) the power transistors and run the blower motor at full speed. If the small board is damaged (has developed some short), it may be switching the relay as soon as the AC/ignition is switched "on". I am not saying this is the case with your controller, just a possibility. Let us know the results after you have replaced the big transistors.
The blower will come on regardless of if the smaller 456 plug is in or out. When the plug is out, I also receive an error code 7. When the plug is in, the ECU lights up normally as if it has control over the speed of the fans. Yet the fans run constant. When I stabbed the violet number six wire I was able to get faring voltage from Low ones to about 5 V on full blast. I really appreciate you responding. Sent from my iPhone using FerrariChat
That shows the AC ECU provides correct speed signal. That is very good news. As for the blower speed controller, see if you can fix it. If not, you can always get one from me (converted controller from another car) if you cannot find a good replacement.
I think you gave me the info I need to get it up and running, but I wouldn't mind have a back up. By now I think you are confident that your mods are better than the original designs. How can I get my hands on one?
Where is the major grounding point for all this blower current ? Are these the same grounding cluster behind the drivers dash vent ? Thanks to all.
I believe it's in the cabin. It's component "100" in the wiring diagrams and there are a lot of things attached to it, including the doorlock module and components on the passenger footwell relay panel, so perhaps one of the spade connectors on the main earthing point behind the relay panel. Image Unavailable, Please Login The earth wire for the controller is spliced into an earth wire for the coil of the blower fan relay (pin 85, I believe) Image Unavailable, Please Login Check continuity to ground from pin 85. If none, check earth 100. There is also an inline 2-pin plug for the earth somewhere (maybe near the firewall... or should I say cabin bulkhead?), but this also carries live battery power from the battery to the 30 amp fuse, so the plug should be connected).
What would be the solution if the HVAC control puts out a steady 6.1 vdc at the violet wire to the fan control module ? This is my situation, as the bar graph digital display works with the buttons but the output of the control voltage does not vary up and down. I assume this causes the relay in the fan control module to close keeping the fan on full speed. Is there a component in the HVAC control that can be replaced ? Thanks, J Glen Wesanko
Most likely the fan (speed) control module itself. The module sends a temperature signal to the HVAC ECU on the violet/white wire and the HVAC ECU responds with a fan speed signal (voltage) on the violet wire.
Thanks for your response Ian. Thing is I have already replaced the module with a New one from Miroljub. I'm thinking there is a component in the hvac ecu that is not adjusting the 0- 5 vdc signal even though the green bar graph display is indicating properly ?
Ah.. that was quick. I can't say I've seen any photos of the internals of the ECU on a 348. Have you rechecked the fault codes?
I often get a an E7 code. Just a note: sometimes the fan control would start working temporarily with a slap to the side of the console. This is why I think there is a problem on one of the "boards" in the hvac ecu. Is there a pwr transistor that operates this 0-5 vdc inthe ecu that can be replaced ?
HVAC plug issues are well known. The looms are sometimes tight and pull on the connector. Perhaps resoldering the connector pins where they go into the circuit board would help. These cars are starting to develop microscopic cracks in the solder at vibration points.
The 0-5V signal comes from a digital potentiometer inside the AC ECU based on the presses of the push-buttons. A digital potentiometer looks like a small micro-chip (picture below) but, in the case of the 348 AC ECU, it is integrated within one of the larger chips so it is not separately replaceable. Perhaps you can try cleaning the multi-pin connectors inside the AC ECU. Info on this I found on the internet is attached. Image Unavailable, Please Login Otherwise, my fan speed controller will default to 50% fan speed if the 0-5V signal coming from the AC ECU is lost/disconnected.
Thanks Miroljub, I think this is my problem. I have had the ecu apart a few times and inspected and cleaned all pins etc. Is there somewhere I could send the ecu to have the component specific replaced ? Could it maybe be a cold solder joint where this digital potentiometer is attached to the board ? Any advice would be appreciated as i've been chasing this issue for years.........
The fan speed controller you built works great! Thank you so much for making one for me. My Ferrari is back from the dead and now fully operational again.
Miroljub, thanks very much for the fan-speed controller you made and sent! In the US Deep South, it's wonderful to have working A/C again!
