Auto AC questions

2008 Kia Rondo, 2.7 liter engine. AC cools for 8-10 minutes and then warm air for the next 5-10 minutes. Thi s action continues on and on.

Please note that this car has an s..load of sensors that may or may not tri gger the compressor clutch solenoid.

Took it to a mechanic (highly recommended for diagnostics)and authorized 2-

3 hours of work. System charge and pressures are right on target. Could n ot find the problem. ($270)

Took it to the Kia dealer ($150 diagnostics) and they agree that the pressu res are fine, but, the compressor is weak. Can replace the compressor for a mere $1,350.

Way more money than what I have. Tempted to wire a push button or toggle t o the relay and mechanically force the clutch to go on while driving.

Kia reminded me that the compressor itself is $800. That leaves about $500 ± for them to play with.

I used to do auto air about 30 years ago when things were simpler. Still h ave gages, leak detector etc. Can't believe that a weak compressor would f or some reason cycle on and off, although I do realize that pressures are p robably being read (sensed)on both the low and high sides of the comp.

Any advise greatly appreciated.

Ivan Vegvary

Reply to
Ivan Vegvary
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Is the high speed cooling fan working? Does the AC stay cold at highway speeds, and only act up in traffic? If so, it's probably the fan.

What are the pressures when it's working, and then when it blows warm? Is it possible there's moisture in the system? Is the air flow through the condenser restricted?

Reply to
Bill Vanek

Bill Vanek wrote in news: snipped-for-privacy@4ax.com:

make sure your evap drain tube is open, may just be freezing up and melting, ect. KB

Reply to
Kevin Bottorff

Thank you for your answer. I will take pressure readings on Friday and report. Thanks, Ivan Vegvary

Reply to
Ivan Vegvary

Bill, thanks for your response. Here are some readings.

Ambient 76°-80°; Relative humidity 72% Turn on car. AC (clutch) engages At 2000 rpm Low=35psi; High=205psi; Cabin vent temp (CVT) = 32° At 650 idle Low= 32psi; H=150 CVT = 28°

CLUTCH DISENGAGES AFTER ABOUT 15 MINUTES.

Only after waiting an additional 20 minutes and trying all controls, includ ing engine off, engine on, clutch somehow re-engages. Tapping on AC relay makes no difference. When re-engaged (by now ambient is 80°) At 650 idle Low=45 High=210 CVT =40° At 2000 rpm Low=32, High=270 CVT=36°

Bill, if this gives you any clues, please advise. As stated previously:

Independent mechanic "Something in the computer module is not triggering th e AC relay. All other voltages, including the thermistor check out OK.

Dealer "Compressor weak" = $1500

Reply to
Ivan Vegvary

So are you saying that the compressor turns off while the readings are steady at 32 & 150? And what happens after it comes back on? Does it continue to work, or does it once again turn off after about 15 minutes? And does the system always behave the same?

There are certain inputs to the computer that will turn off the AC for protection or other reasons, and I can't remember what all of them are. WOT will turn it off on at least some cars, and high coolant temperature, and I'm sure there's other things. Is the engine getting hot? Can you read the coolant temperature?

I am also assuming that you know that the clutch is not being commanded on, and failing to engage.

If those readings do hold steady at 32 & 150, and it still turns off, there is either another AC system sensor that I'm not aware of (I'm not familiar with this car at all), or another input to the computer telling it to turn off the AC. It does not sound like the cooling fan. Do you have a wiring diagram that shows all of the sensors?

Even though it doesn't sound like the high speed cooling fan, is that fan coming on?

And it seems that the only way it could be the compressor is if it's being commanded on, and not coming on because of the coil, or a wiring issue at the compressor.

Reply to
Bill Vanek

There is one other thing. I just Googled this, and I noticed that your outlet temp was 28 degrees. There is a thermistor on your evaporator that might be shutting the system down. 28 degrees seems awfully cold, but I don't know what is supposed to prevent that on your system. Is it a cycling system?

Reply to
Bill Vanek

In addition to the things others have mentioned I would take a look at the low pressure switch IF your system has one. On my vehicles it's a switch with two wires on the low pressure (should feel cool or cold) line. When the pressure drops to around 28 psi it clicks off and shuts off the compressor. If it doesn't click back "on" then naturally the compressor won't come back on. You can pull the connector off it and just jumper the connector so that it's always on and see if that keeps the ac running after the 15 minutes goes by.

If the evap coil is freezing up you should notice a reduction in airflow thru it. I've had cars where it would freeze up and the airflow would get cut in half and it would not be very cool, but it's usually still going to be somewhat cool rather then warm even if it freezes up.

Reply to
Ashton Crusher

you don't say if it is the Automatic or the Manual system but in either case the compressor is turned on by the relay, and the relay is controlled by the PCM. The PCM is /told/ whether or not to control the relay by the AC control module. The AC control module is the one that gets sensor input. Without the proper scan tool there is no way to tell what the ACCM is telling or not telling the PCM. Either of those modules being defective is just as likely as anything else. But whether or not the compressor stops on it's own (dies) or is disabled (turned-off) by the relay can be checked the same way you did on a car in the 1980's. (hint: test-light)

Wiring a push-button will likely just ruin the thing worse than it already is. Even in the 1980's you needed the hi and low cut-off switches working.

GW

Reply to
Geoff Welsh

So the system is working properly, but then something gets out of range, and it shuts the system down.

How many in an assload? Three? Five? Find them, put a meter on each and watch what happens when the system shuts down.

The pressures either aren't fine, or a sensor is bad. Were either of these guys able to make the system shut down? Or was it behaving for them? If they can't get it to fail, they'll never find it.

There is a reason why it's shutting off and that COULD be because the pressures are all wrong. Maybe the evaporator is icing up when it's humid. If it is something like this, you'll damage things if you force it on.

On the other hand, if it's a bad sensor, you won't.

There's nothing wrong with the compressor. Not yet, anyway.

They are, and you need to have a meter on those sensors. If the high side switch is shutting the thing down, and at the same time the high side pressure is fine, you have a bad switch.

The system really isn't any more complicated than it was 30 years ago, it's just the manuals make it look that way. And there is usually a control computer in the loop (which does nothing important and probably isn't related to the problem, but the meter will tell you for sure).

--scott

Reply to
Scott Dorsey

somehow me thinks all that real estate on prius wanna be computer screens showing turbo pressures corenering G and the flow of power/charge (other nonsense etc) could've been used productively showing the useful diagnostics, in the A/C systems in particular, show the freaking voltage as a default if nothing else, not sure how many consumeristas walking into a new car lot can appreaciate that, guess not a whole lot :-[

Kill a few marketroids: make the world a better place to live in

Reply to
isquat

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