[Florida] AC went out last night. CEL on today.

[Safraz]

My AC stopped blowing cold air last night. I ran it for a while to see if it would cool. Unfortunately, it didn’t. Today, while I was driving, the CEL came on.
I took the car to both AutoZone and Advanced Auto Parts for a diagnostic. Both times, I got the P0420 code (Bank 1). The young man at AutoZone said his system referenced this code to the catalytic converter. The man at Advanced Auto Parts said it could be the O2 Sensor (Bank 1, Downstream).

Do you think this caused the AC to stop blowing cold air? By the way, when I opened my hood, I noticed that the insulation that is on the underside of the hood was torn up and large pieces were lodged behind the engine.

Also, I just tested the Climatronic to see if maybe the temperature sensor had gone bad. When I turn it all the way to LO, it blows warm air. When I turn it all the way to HI, it blows hot air like it’s supposed to. The AC was recharged two months ago. I only really started using it last week when the temperature started to go up down here. I also replaced the valve in the compressor before the AC was recharged.

Car: 2006 VW Jetta GLI 2.0T FSI MKV

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[Timothy Salomon]

As the catalytic converter goes bad, the p0420 code often sets on long trips. I don’t think the AC is related to this issue, except the long trip may have revealed an existing problem. Test the o2 sensor before replacing it, because there are codes for o2 sensor failure and p0420 isn’t the primary code for that.
You can use a recharge kit from any auto parts store to check the pressure in the AC system, and you can also listen for the AC compressor clutch engaging to diagnose the air conditioning problem.

[Safraz]

Thanks for the feedback. What you mean when you say “long trips”? I had my dad follow me today. He said that thick black smoke was coming out of my exhaust, especially when I was accelerating. As far as the AC is concerned, I looked at the compressor and it was spinning like it normally does. The fans, however, were not. This compressor does not have a clutch so there is no sort of clicking sound to listen for.

[Jim Davis]

I agree with Tim, your problems are not related, usually. The fact they both started so close together, and you describing the insulation down around the engine, I think your first line of attack should should be a thorough inspection of ALL the wiring harness, looking for pulled wires, cuts, pulled connectors, blown fuses, etc. Not sure whats on your hood, but some of that insulation is pretty stiff stuff and torn loose, with the air turbulence under the hood could very well have done some wiring damage.

[Timothy Salomon]

Long trips? More than 1/2 hour on my truck will set this p0420 code. But black smoke isn’t good either. It may be getting too much fuel or running “rich” a scanner with live data could help, but making sure the temperature sensor and oxygen sensors are connected might be a good start.
Also if the exhaust smells like unburnt gasoline that might be another clue.

[Larry Bible]

I fully expect that the problems are coincidental and not related.

To the a/c: you need to have someone connect manifold gauges to begin the a/c diagnosis.

Hope this helps,

[Author]

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