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Nissan 2000 xterra air conditioning and knock sensors

Recently, a friend of mine took her 2000 xterra to a Goodyear dealership to have her A/C checked. She would drive the car for a while before cold air would come out of the vents. Goodyear said her compressor was shot and replaced it. When she got it back with the new compressor, it was still not cooling the car. I noticed that the compressor would not engage sometimes until about 5 minutes after the A/C switch was turned on. In my Nissan Maxima, the compressor kicks in as soon as I turn the A/C on.

Upon returning it to the Goodyear dealership, she was told the freon leaked out as they found 2 leaks, but yet they stated that they took the system into a vacuum at 2 psi for an hour and a half and there were no leaks when they first replaced the compressor. Their response to my reminder about this was the Shrader valves (not sure of the spelling). The Shrader valves were replaced. During the repair of the new compressor, the mechanic could not get the car started, they replaced the starter, which worked fine when she brought the car in to have the new compressor repaired but the new starter did not solve the problem and supposedly replaced the original starter and then told her there was an extra cable to the starter that they weren’t sure was there for coming from a relay I believe they said. Since the starter fix didn’t work they then thought the problem was with the alarm system. She sent them her wireless key as she only left them a door key. She was called and said the car was ready. When picking up the car, upon starting the car and turning on the A/C switch, the compressor did not kick in right away. It kicked in after a few minutes AND her check engine light was now on. It was not on when she dropped it off to have the new compressor repaired. She was told the code referred to a bad knock sensor and that it would be her responsibility to have it repaired as they are not equipped to do that repair. All she wanted was her A/C fixed and went through a starter, alarm problem and now a knock sensor problem in the process of getting her A/C fixed. 2 questions- Are the Shrader valves part of the compressor and if not, could her original compressor have not been the problem and the Goodyear dealership was just pulling parts at her expense to resolve the issue and her new problem with the knock sensors, can it be rlated at all to the work done replacing the compressor and removing and replacing a starter twice? Is ther check engine light coming on a coincidence?

This isn’t an auto shop…it’s a butcher shop.

There’s no way to tell now if the old compressor was really bad. The problem may have been serious leakage. But I can tell you that they botched the AC repair big time. Then charged and charged and charged again while they stumbled through the process in total darkness.

I can also tell you that their failure to be able to diagnose a no start condition…simply throwing in a new starter…and then having a cable left over…would be source of shame to most techs. Even shadetree techs. It’s simply too easy to determine if the starter is bad. And too basic a process to change it.

There’s no way of knowing either if the knock sensor is really bad. I seriously doubt if it is. They simply are not competant enough to check the sensor itself. It’s a simple accelerometer that either changes its resistance to shock (piezoresistive) or sends a signal (piezoelectric). Checking it involves advancing the timing and checking for the proper signal response. Way beyond these Bozos. It’s also possible that they tripped it, and the code is that preignition was detected, and the ECU will reset itself.

Get this vehicle to a real garage pronto!

Yes, there is a schreader valve for recharging the system. Don’t let them near it.

They probably damaged the knock sensor or wiring while changing the starter.

Use a specialty shop for AC repairs and get a reason why a paticular part is bad (if you can’t understand what they are saying have them write it down for you and let us or someone else look it over)

Perhaps that extra wire dangling down by the starter went to the knock sensor.

I also have and Xterra,…2001. it has an intermittent starter and AC problem.
Recently the starter would not turn over after 100 tries. I opened the relay box, which has a starter…and AC relay switch in it. I wiggled it back and forth a few times, and it started up right away. Also I tried the AC and it kicked in too. Which it usually doesn’t not right away. I also had the starter and battery replaced last year.

A schrader valve looks like a tire valve and there may be two of them in the AC system, at least one is high pressure. They are a non-event here. If the shop can’t change a knock sensor, they have no business working on AC. Their results show that they don’t. You may have to go to an independent repair place as well as an independent AC shop. It’s not that you can’t have the same place be good at both, but sometimes it works ot that way. Even the Goodyear place could have been all right but not that one.