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AC Sensor/Switch Issue Related to Cooling Fan

 
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Old 09 May 2015, 04:58 pm
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Default AC Sensor/Switch Issue Related to Cooling Fan

Hello All,

This is my first actual post on the site, but I have used the information I have gleaned from the site for some time....Thank You!

I have the dreaded cooling fan issue. After reading many articles here, I replaced the fan, and the relays on the shroud (took some work to find the right ones). I am still having the issue with the fan not coming on. At idle I also get (after a little time with the A/C on) some rpm dropping and almost stalling.

After reading some articles, it seems that this could be related to to the A/C compressor building up too much pressure on the "high side" because of the fan not running. When I am moving, no issues. Along those lines I have been researching the A/C Compressor Switch to replace it. It seems from some articles that this could fix the issue related to the fan and thus the idle A/C issue.

Now to the question....

I am trying to find out where both the high and low pressure switches are located. I see the one on the back left (standing at the front of the car) that is extremely accessible....looks like an easy job. AZ shows the same switch for both the high and low, but are unable to tell me where they are and/or which the one I described above is.

Any help/advise would be welcomed.

Thank You All In Advance!

BTW I have a 2007 PT Cruiser 2.4 Non-Turbo, Non-Convertible, "B" code.

Last edited by swanley007; 09 May 2015 at 04:59 pm. Reason: Cruise Model Type Addition
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Old 09 May 2015, 05:40 pm
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Location: Thousand Oaks, CA
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

When you start the engine cold and you turn on the A/C is the compressor clutch engaging?
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Old 09 May 2015, 08:24 pm
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

Without going down/out to the car right now (it is still warm anyway), my answer would be yes. The A/C does initially blow cold and then the issue will start after a little time (few minutes from cold). When the rpm cycles begin, the a/c blows cool air, but not cold by any means...both clear up when moving.

I can open the hood and listen for the clutch to engage next start-up, but I am pretty confident that it is working.
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Old 13 May 2015, 09:31 pm
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

OK...New Information to report.

I thought it was the A/C causing the idle drop sequences. I am not sure that is the story now. When I start the car the A/C clutch does engage and there is cold air. This goes on for a while and then the oscillations begin and no cool air.

BUT...New info after watching and listening and trying a couple of things.

I ran the car to normal operating temps. Then I let it sit idle with no A/C on. I heard the clicking of the fan coming on. Then the sequence was...

Click (Fan On)
RPM Drastic Drop and Lights Dim (almost stall)
Click (Fan Off)
Idle returns to normal
REPEAT

This repeated (about every couple of seconds) until I shut the car off for a few moments and allowed the car to cool some. This was happening around the midpoint for temp on the gauge.

When I restarted, the fan Clicked On...the idle became very rough while the fan was on (worsened by the A/C on) and even got a Cylinder 3 misfire code. The fan clicked off and the roughness got much better. I had to move (due to traffic situation) after this and the driving cooled the engine and no issues while driving and not at idle.

Could the battery be bad, and when the fan is "pulling" on the system causing the Alternator to work overtime and causing the RPM oscillations? Since the fan is off...on...off in this sequence the A/C is not able to cool and hence the high pressure issue.

This is a weird problem and I am really beginning to scratch my head. I am out of town with the car right now and hesitate to take it in somewhere I am unfamiliar with.

Any Help is great!
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Old 13 May 2015, 10:13 pm
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Location: Thousand Oaks, CA
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

My radiator fan on my 2007 PT Cruiser had the same problem. I bought another radiator fan from Rockauto for $84.00 plus shipping and it solved the problem. One thing I don't hesitate on doing is replacing the radiator fan. The possibility of overheating the engine is high when you start having problems with the radiator fan. I even have a brand new one in the garage in case the radiator fan starts to fail in either one of my PT Cruisers.
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Old 13 May 2015, 10:43 pm
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

Issue here is that this is a brand new fan( also replaced thermostat, cooling fan relays, spark plugs, spark plug wires, and ignition cool)....and new coolant fluid.. Not only that, but I returned the first one thinking it was a DOA unit. This is the second new out of the box one from Advance Auto. The likelihood of 2 being bad is very low, but not impossible.


Thoughts
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Old 14 May 2015, 12:37 am
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

I would suggest checking your engine coolant temperature sensor. Check the wires going to it and make sure it making good contact.

I would also suggest checking for weak grounds. Check battery cable contacts. I do a battery load test on the 2007 PT Cruiser when I start having electrical problems.

You have several ground wires going to the inside drivers fender. Its hard to see all the wires underneath each other and some of them may not be making good contact. I would suggest start adding additional ground wires if you plan to keep the PT Cruiser for a while.

On the 2006 and 2007 PT Cruisers there has been some electrical problems due to weak grounds or TIPM. On my 2007 PT Cruiser I replace the battery in that one every 18 months to keep the dancing gauges from triggering.
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Old 16 Jul 2015, 01:36 pm
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

High & Low relays are mounted to the radiator. When facing the engine they are on the left side right below the oil dip stick.
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Old 16 Jul 2015, 03:37 pm
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Default Re: AC Sensor/Switch Issue Related to Cooling Fan

When you purchase the new fan the relays come with it. As noted above the high and low speed relays are mounted on the shroud and are all replaced at once.
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