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AC clutch works when jumping relay (and it makes cold air!)
Low speed cooling fan works under normal car operation, but does not come on when AC button is on
Car has Auto HVAC controls
Recirc button does not work (testing via INPA shows button works, but recirc does not turn on)
Rear Defrost - same as recirc above
Checking via INPA shows the demand for AC cycles on and off, never tells the compressor to come on. Oddly, I cant manually turn compressor on via INPA
I am at a loss - checking schematics, I see reference to a General Module that handles some things, and the BCM which handles other things? But my google research says the GM and BCM are the same thing??
This car had significant water damage to the X15 connector under the fuse box in the left kick panel - so much that we cut the connector right out and soldered all the wires together for a total bypass. This damage was due to a disconnected sunroof drain. Oddly, the right side sunroof drain was connected and clean, so I am not sure if water ever really hit the BCM.
Sadly at this point, I am really suspect of the BCM, but looking for other options before I decide to try chasing one down....
What else can I look for? Did I miss something to check? Really frustrated, as I was hoping I could finally have a car with AC for myself LOL
You may want to check the fuse for the power steering pump fan. If I remember correctly depending on the model year if it's blown it can prevent AC from working properly.
I will double check it, but I have looked at it before (couple weeks back when I first got the car, we checked every fuse trying to figure out some of the electrical gremlins caused by the X15 connector)
If the pump fan has locked up it will blow the fuse. You might need to crawl under and try to spin the blades with something small to see if they rotate.
AC Problem tabled for the moment.... King Bob is bruised, King Bob is battered.... But... King Bob is not bleeding at least! The deer, did not fair so well...
So, since I am not able to drive it at the moment, I took the time to look at fuses...
All fuses that are present and accounted for, are good.
Using the diagram that I have handy, I see one missing that maybe should be there? Fuse 38?
I attached a picture of the fuse box, as I am sure there are plenty of people smarter than me when it comes to these cars.... that can look and determine if I am missing an important fuse!
Ok, research shows me the empty fuse slots I have are appropriate for my car. That said, all fuses are present and accounted for, and they are good.
I am pretty sure I am back down to BCM....
'good' news.... is I have located a parts car for the deer damage repair... and it should have a BCM... bad part of that is, its a non-sunroof car.
I do hope that I can still use that BCM to prove/disprove the AC problem is BCM related? Or can I just use that BCM and enable the sunroof functionality using NCS Expert?
Well, yanked the BCM from the parts car yesterday, and swapped it in. No Bueno.... AC still doesnt work, oddly my rear defrost and recirc also still dont work.
Factory BCM is back in the car... and back to the drawing board!
Before you go the full BCM route, you need to ensure all the pre-conditions for AC to enable are checked. I don't know them all, but something as innocuous as a bad reading from the temperature sensor (environmental, not coolant temperature) can disable AC permanently. A friend had that issue on a 2nd gen because his temperature sensor was broken and we want pretty far before making the link.
Edit : oops you already went the BCM route and it didn't work ... Well, that's your next thing to do, and for anyone reading in the future, something to do BEFORE trying to replace the BCM.
Being that i had electrial issues in the car due to the faulty x15 connector, there was a poing where the ambient temp sensor was giving faulty readings. I have it working now... but obviously it didnt make any difference.
Originally Posted by Fradow
Before you go the full BCM route, you need to ensure all the pre-conditions for AC to enable are checked. I don't know them all, but something as innocuous as a bad reading from the temperature sensor (environmental, not coolant temperature) can disable AC permanently. A friend had that issue on a 2nd gen because his temperature sensor was broken and we want pretty far before making the link.
Edit : oops you already went the BCM route and it didn't work ... Well, that's your next thing to do, and for anyone reading in the future, something to do BEFORE trying to replace the BCM.
Being that i had electrial issues in the car due to the faulty x15 connector, there was a poing where the ambient temp sensor was giving faulty readings. I have it working now... but obviously it didnt make any difference.
Oops, indeed, "permanently" was the wrong word. I meant "until it's fixed". Time to find what all the other conditions are and check them via OBD2 to see what's up. Also ensure the AC charge is correct (not too high or too low).
*sigh* just tossed it on the ac machine, recovered the refrigerant, and did a complete recharge.... and as I suspected, no change. I had hopes maybe the pressure was off. :-(
I worry that its related to the fact that the rear defroster, and the recirc wont turn on. Oddly, both those buttons when pressed are seen by the BCM.
I will head back out shortly with the laptop, and take a better look....
It's an unlikely lead, but could you test for continuity on the electrical circuit? Again you'll have to figure what's supposed to lead to what, but more or less (hopefully I got the order right):
battery positive lead should have continuity with a side of the AC compressor fuse (or with the relay, I don't know in which order they are)
the other side of the fuse should have continuity with a side of the AC compressor relay (I'm assuming the AC compressor has 2 pins and the relay is in the fusebox, but if it's 3 pin you need to test both the power and signal pins)
the other side of the AC compressor relay should have continuity one of the AC compressor pin
the other AC compressor pin should have continuity with ground
a bit sketchier, but with the car on and the AC compressor plug removed, test that the plug receives power when the AC is turned on.
Not sure if I stated this before, but if I pull the relay, and jump the pins, the compressor comes on, and AC works fine.
I think I need to start back tracking from the relay coil wires and seeing where that gets me.
Another tidbit, the low speed fan doesnt come on with AC request. But I am not sure if that is automatic once the AC is turned on, or is temperature related to the system? (my MK4 Jetta I had as soon as you turned the AC on, the low fan would come on, and if it didnt, the AC wouldnt work)
Originally Posted by Fradow
It's an unlikely lead, but could you test for continuity on the electrical circuit? Again you'll have to figure what's supposed to lead to what, but more or less (hopefully I got the order right):
battery positive lead should have continuity with a side of the AC compressor fuse (or with the relay, I don't know in which order they are)
the other side of the fuse should have continuity with a side of the AC compressor relay (I'm assuming the AC compressor has 2 pins and the relay is in the fusebox, but if it's 3 pin you need to test both the power and signal pins)
the other side of the AC compressor relay should have continuity one of the AC compressor pin
the other AC compressor pin should have continuity with ground
a bit sketchier, but with the car on and the AC compressor plug removed, test that the plug receives power when the AC is turned on.
Not sure if I stated this before, but if I pull the relay, and jump the pins, the compressor comes on, and AC works fine.
You might have mentioned it already, sorry. Still worth checking if you have continuity between the relay control side and the BCM, just in case.
Originally Posted by mangus580
Another tidbit, the low speed fan doesnt come on with AC request. But I am not sure if that is automatic once the AC is turned on, or is temperature related to the system? (my MK4 Jetta I had as soon as you turned the AC on, the low fan would come on, and if it didnt, the AC wouldnt work)
The AC can work even if the low-speed fan doesn't (I had the resistor broken for a while, and the AC did work regardless).
Turning on the AC should make the low-speed fan come on (if it works). I've not paid attention to that, but have seen it mentioned multiple times.
If you have a known-working low-speed fan, and it doesn't come on when you request AC, it's likely your BCM isn't triggering the AC due to other conditions not being met. A quick check: remove the relay and see if the control side of the relay is getting a signal when you turn the AC on.
The key points apart from continuity test (copied from the write-up):
Ensure that there is A) charge in your ac system past 25 psi. you can confirm this using a viable scan tool. (or u can tap a schrader valve on the low side with a screwdriver and see if theres refridgerant still in it but you didnt hear that from me)
B) power to your pressure sensor located at the back of the intake box towards the firewall on the high side line.
C) Proper ambient temperature levels/a working ambient temperature sensor.
You checked A) already, for C) I'm assuming you aren't in scorching hot heat and you said the ambient temperature sensor is working, so that leaves B) : checking that the AC pressure sensor is working. The write-up is for a second gen, but first-gens do have one as well, you'll have to locate it (or see if that info is available via OBD2 to know if the car has a proper value).
