i think i smoked my ECU (02 alh) -replacement?

[jerryfreak]

was sitting in my car and the cabin filled with burning electrical smell.. and my AC hasnt worked since. my mechanic has traced it from the compressor clutch back to the ecu and says he cant get past there. thinking it burned up and thats what i smelled (it live in the cowl with the intake air aferall)

i have another onei grabbed from a alh 5 spd (same as mine) in the junkyard, but cant remember what year it was. i imagine these need reprogrammed? can vagcom clone mine?

hot as heck im ready to throw a manual toggle swithch on the compressor to see if that works when i want to run it ful tillt

car has 240K but many miles left so ill rig it if i have to -- just want AC again!

 

[jerryfreak]

the extra ecu i have here is 038 906 012 FD

not sure whats in the car

 

[AnotherPerson]

the extra ecu i have here is 038 906 012 FD

not sure whats in the car

If you have vcds you can pull your ecu PN


Sent from my iPhone using Tapatalk

 

[jettawreck]

If you just swap ECUs I don't think the immobilizer is going to be happy about it.

 

[RexNICO]

I have a matched set (ECU, Cluster & FOB/RFID), but they're from an 03. I think year is very important.

If you find a good/matching ECU, you can probably get the IMMO defeated for ~$60.

Good luck

 

[Alchemist]

The AC compressor clutch is operated by the Fan Control Module, not the ECU. I think your mechanic is barking up the wrong tree.

 

[mk3]

Hook VCDS tool to the car (to the ecu) and see if it will talk to you.

Is the relay that turns on the compressor clutch inside the cabin? On the B5 it is so if wires near that melted you would smell them.

not sure why a fuse wouldn't have blown though. Are all of your fuses OK, especially those related to AC?

 

[jerryfreak]

revisiting this now that its super hot out

fuses are good, where is the relay? i believe the FCM is under the battery tray, how to test it?

 

[csstevej]

First off does your two fans run when ac button pushed to on? If yes don't worry about your FCM yet.
Check the resistenance on your coil for the compress.....I'm willing to bet that's where your smoke came from. If it's open then it's bad. At the same time check and see if you have 12 volts on the other side of connector with the ac switch on and at least a fan speed of 1 selected in car.
Check that out first.

 

[tgray]

Do a search - there is a good write up on this forum of a step by step process to troubleshoot the A/C Everything needs to be checked in order and working for the A/c to turn on. There are a lot of possibilities for problems. I had a pressure sensor short out, blow a fuse and also take down the ABS - that was difficult to find but easy to fix. The biggest problems I have found are the A/C clutch fried, wires in the plug to the clutch, FCM, pressure sensor switch and the fans themselves. Anyone of which can blow smoke and smell. The ECU is about the last place I would think to look.

 

[jerryfreak]

with the car cold both radiator fans are off, and when i turn AC on the smaller of the two comes on

the wires leading to the compressor clutch show a little over 9V with the AC on. then i test it later and its 3V or 7V ot 5V- ots completely erratic and also energized when the AC is off!

im measuring the resistance across the two wires that go to the clutch as open resistance

i tried to put 13V from the battery to the compressor clutch had a little spark when connecting but the clutch didnt lock. wasnt sure of the polarity when i connected it as my mechanic busted the connector and had it rigged with spade terminals. i tried it both ways to no avail

looks like orange and black wires coming down (and looks like those arent original)- orange is hot

yellow and blue to the clutch- is one of these grounded?

 

[csstevej]

Well you have a problem with the large fan, either with the wire to it or the connector, or the fan.
See if you can run two wires to it , I'm not sure which but one way is high speed the other low.
You comp clutch is done, you need a new one if you have an open. It's not hard to change but you do need some deep snap ring pliers to get to the 2 snap rings in there.

I think if you put the right connectors on your flakey voltage will go away.

 

[jerryfreak]

so both fans are supposed to come on with AC huh?

are both wires to the big fan 12V, and its grounded to frame?

re: clutch, do i need to pull the belt or does the clutch pop out of the middle?

re: the voltage going to the compressor clutch ive got a solid measuring point on the terminals, i think its buggered farther up in the circuit. where do those leads originate from?

thanks

 

[steve6]

so both fans are supposed to come on with AC huh?

are both wires to the big fan 12V, and its grounded to frame?

re: clutch, do i need to pull the belt or does the clutch pop out of the middle?

re: the voltage going to the compressor clutch ive got a solid measuring point on the terminals, i think its buggered farther up in the circuit. where do those leads originate from?

thanks

I think your clutch coil is just bad.. check the resistance of it, should have resistance, if its a open circuit its toast. When you jumped it and it sparked it leads me to believe that is why the voltage is wonky. You do need to remove the belt to replace the compressor clutch.

Both fans should come on IF the a/c system is kicking in. If one is coming on but not the other its most likely bad. Try turning it by hand, lots of time they lock up, others ive seen have melted inside so the brushes no longer made contact. The fans have low speed and high speed, just worry about them working.


lots of good info right here http://forums.tdiclub.com/showthread.php?t=242699

 

[jerryfreak]

I think your clutch coil is just bad.. check the resistance of it, should have resistance, if its a open circuit its toast. When you jumped it and it sparked it leads me to believe that is why the voltage is wonky.

thanks for the link. just to be clear voltage is wonky when completely disconnected from the clutch. so while the clutch burning/shorting out may have caused that, as of now there appears to be other electrical damage