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I had a muffler place install my dp recently. They used a torch to loosen the bolts by the o2 housing and must have torch the o2 sensor as well because it's not reading properly anymore. The sensor thinks im running very lean! I read somewhere that the coumputer shut off the A/C went your rev's get high to protect the engine or a/c. Could the o2 sensor be at fault why my a/c is not blowing cool air. The blower works but no cool air comes out. I don't hear the compressor also.
 

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Humm I don't think the ecu does that. (I'm realy not sure) Because if that was true then why do cars overheat and the a/c is still pumping. I would try to replace the 02 How old is it? If it was new then I would make the mufflar shop replace it for free. Also remember you have 134a and that shit can uncharge.
 

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Discussion Starter #3 (Edited)
sorry i mis-understood

TechnoMotive Convenience Modifications
Imagine the following scenario. It is a hot, sticky, August afternoon. You've been running errands all day in heavy traffic. You've got the air conditioning on full blast, and it is barely keeping up. Finally, the last errand is complete and you are on your way back home. The traffic starts to thin out and the drive becomes more pleasant. You miss the last light right before the expressway, and end up first at the red light. On your left, someone pulls up and starts revving their engine. Well, you are not one to recklessly race on the street, but the road ahead looks clear enough - you decide to give the guy a lesson in 0-60 acceleration. You hit the light perfectly and launch well, but soon you hear a low pitched growling whine from the engine as its RPM goes over 4000, and the engine doesn't feel as strong as it normally does. You move to second gear, but get the same results - and you see a blur go by on the left. Ooops! You forgot to turn off the air conditioner!

Wouldn't it be nice if the engine computer turned off the air conditioner when the RPMs got too high or when you put your foot through the floor? There is really no reason why it can't-on the DSMs, the ECU has direct control of the air conditioner clutch relay! Not only are you robbed of performance due to the drag of the air conditioner compressor, but you are risking the health of the compressor by driving it at such high RPM. A couple people have actually had the compressor "explode" when they missed a shift and ended up driving the compressor at over 7000 RPM.

This is a perfect example of a convenience modification. This modification does not really affect performance of the engine directly (after all, you can reach over and turn off the A/C yourself!), but makes the ECU do something nice and convenient that the factory could have programmed in from the start.

Here are some simple things we've added that we believe should have come from the factory.

Better handling of air conditioner - The A/C compressor turns OFF if past 5000 RPM or throttle past 85% - will return to ON if RPM remains below 5000 and throttle below 85% for more than 5 consecutive seconds. (By the way, we don't advocate driving beyond the limits of the law, of your abilities, or of your car's abilities, but theoretically, if you happen to be in Montana, 5000 RPM is good for about 104 mph cruising, higher on non-AWD models.) Note: The second generation ECUs come from the factory with the 85% throttle shutoff, but do not have the 5000 RPM limit.



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I've replace both o2 sensors about 7-8 months ago and my air/fuel gauge was working up to the day before my dp was installed. After that my gauge is reading very lean or not at all.
Since the ECU has direct control of the a/c clutch relay, could the very lean reading from the o2 sensor affect the ECU's judgement over the a/c clutch relay.

Does this makes sense?
Because the o2 sensor thinks i'm running lean very lean (even at idle), i must be running over 85% throttle therefore the ECU is shutting down the a/c to protect the compressor.
So if I replace the o2 sensor the a/c will work again.
 

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Re: sorry i mis-understood

zoomail said:

I've replace both o2 sensors about 7-8 months ago and my air/fuel gauge was working up to the day before my dp was installed. After that my gauge is reading very lean or not at all.
Since the ECU has direct control of the a/c clutch relay, could the very lean reading from the o2 sensor affect the ECU's judgement over the a/c clutch relay.

Does this makes sense?
Because the o2 sensor thinks i'm running lean very lean (even at idle), i must be running over 85% throttle therefore the ECU is shutting down the a/c to protect the compressor.
So if I replace the o2 sensor the a/c will work again.
Some things:

1. Your ECU can shut down your A/C once it's modified by Technomotive.
2. A dead O2 sensor will cause your car to run rich, not lean. I think that you're going by what the A/F gauge (if you have one) tells you. If the A/F gauge stays on the red (lean) side everytime, it means that your upper O2 sensor is dead. However, it doesn't mean that your engine is running lean. That's the reason that the disco party autmotemer a/f gauge (unmodded) is a big POS. :rolleyes:
3. It might seem stupid, but have you check the A/C temperature switch (the one that is small and has a snowflake on it) is pushed all the way in? Sometimes one can hit the switch and make it come out, which makes the A/C blow hot air only.
 

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I had a muffler place install my dp recently. They used a torch to loosen the bolts by the o2 housing and must have torch the o2 sensor as well because it's not reading properly anymore. The sensor thinks im running very lean! I read somewhere that the coumputer shut off the A/C went your rev's get high to protect the engine or a/c. Could the o2 sensor be at fault why my a/c is not blowing cool air. The blower works but no cool air comes out. I don't hear the compressor also.
Years later reply here but I had a similar issue and ran into this thread. Did you ever figure out what was the issue? I'm going through the same deal after dropping my transmission on my '10 mustang. I found that I forgot to connect an O2 sensor back and the connection had gotten melted on the muffler. I think as a result my A/C Clutch relay has shorted out and caused my AC to stop working. Thoughts?
 
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