What's new
By:
Advanced search…
Club Scuderia

This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

  • Please take a minute to read this thread about our recent server issues and forum platform Switch

355 HVAC airflow control not working

R

Red_SLR

Member
I have posted on FChat about this but thought I would ask more local people.

I have lost the control over the air direction (feet / dash / demist) on my 355.

I bench tested the mixer motor (that moves the flap that controls the airflow) and it works fine, nice and smooth and quiet so it was pointing to the ECU being at fault.

I sent the ECU off to be repaired and they replaced the 6 drivers for the main functions and also 1 thermistor.

Thats now been re-installed and the air mixer direction is still not working. Further bench testing of the motor unit shows that it does seem to be ok, the readings from the potentiometer is within spec and does match up with the end stops. So its not likely to be the motor itself.

With the motor off the car the following happens. If you leave the motor all the way at one end stop when you ignition on the motor does a sweep and then parks.

Then if you move the position switch from say feet to demist the motor moves about 1/8th of a turn then bounces back to where it was. Almost like it is trying to move to the right spot then something happens it does not like and it returns to its spot. It does not matter which position you select it does the same.

So now I am looking at either a faulty switch on the HVAC panel or a wiring fault?

Dont suppose anyone in the NW has a spare HVAC panel I could test ? Its a 1 min job to swap them out.

Any one been through similar? TIA!
 
I have just checked the switch on the HVAC panel and it seems ok. I buzzed it out in its different positions and it jumps from one resistor to another so that to me seems typical operation? The fan speed switch (also a 6 position switch) works in the exact same way.

So I think the switch is ok.

My next task is to try and check the wires from the switch to the ECU is ok...
 
Is it the same system as on a 348?

I had some random gremlins with mine when I got the car, AC randomly coming on when heat was selected, some functions not working, that sort of thing. Was solved by removing the wiring sockets (not sure of the correct term) off the back of the control panel, healthy does of contact cleaner in the wiring sockets and contacts they attach to on the back of the control unit then put it all back together. All the gremlins disappeared never to return. If you've not yet done this it may be worth a go if only to discount faulty contacts between the control unit and wires going to the motors.
 
Last edited:
Hi all fixed! It seems it just needed a proper battery re-set to relearn.
The ECU was fixed by a company in Liverpool if anyone needs their details let me know they were very knowledgable on these units.
 
355 HVAC ECU Problems

Red_SLR said:
Hi all fixed! It seems it just needed a proper battery re-set to relearn.
The ECU was fixed by a company in Liverpool if anyone needs their details let me know they were very knowledgable on these units.
Click to expand...

Hi RED_SLR can you please advise me the ECU repair company in Liverpool that fixed you HVAC ECU? I have similar problems to you. Also if anyone knows a of good 355 HVAC ECU (64324800) that would be really helpful and if anyone has aunit for sale.

Thank you.
 
@328355 I contacted Simon via PH and found out that he used a company called Crash Data in Liverpool. I've contacted them about my HVAC ECU and will let you know how I find them.
 
redwedge said:
@328355 I contacted Simon via PH and found out that he used a company called Crash Data in Liverpool. I've contacted them about my HVAC ECU and will let you know how I find them.
Click to expand...
Hi, I wondered if you got a response from Crash Data regarding your f355 HVAC ECU? I am having problems with my air director and having replaced the mixer motor I'm now looking at options for replacement or repair of the ECU.

Cheers

Andy
 
I did Andy - they wanted £216 which I didn't think was too bad, but they were unable to tell me what they actually did, so I didn't send it in. I am probably going to get a local shop to take a look at it if they can repair my broken MacBook which needs a couple of chips replacing.
 
redwedge said:
I did Andy - they wanted £216 which I didn't think was too bad, but they were unable to tell me what they actually did, so I didn't send it in. I am probably going to get a local shop to take a look at it if they can repair my broken MacBook which needs a couple of chips replacing.
Click to expand...
Thanks for the update. Sounds like you know what needs fixing on your control unit; is your problem the same as the OP and how did you diagnose what needs fixing on your controller?
 
Water valve works when voltage is applied. Resistance on the pot changes when it turns. Loom has continuity. So the only thing left is the ECU, which is going to be the op amp ICs.
 
Top