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That Mitsubishi again

AC Amiture on Sun September 21, 2008 3:43 PM User is offline

Year: 2000
Make: Mitsubushi
Model: Mirage
Engine Size: 1.5
Refrigerant Type: r-134
Ambient Temp: 90
Country of Origin: United States

Problem is intermittent.

When car has been sitting for an extended time (over night) clutch pulls in and AC cools. After the AC runs for a time and is turned off, the clutch will not engage when it is turned on again.

After some trouble shooting, I decided that the most likely problem was the pressure switch. I checked to see that the there is 12 volts at the switch and then jumped it. When I jumper the switch out, the clutch engages and system runs normally.

Do you think it's a bad switch or something else? If it was the switch operating normally (high or low pressure) wouldn't it just disengage the clutch while the system was operating or never allow the clutch to engage if the pressure was low? Why does it only open after the system operates and is shut off then work again after enough time passes?

Any advice you have to give is appreciated.

bohica2xo on Sun September 21, 2008 4:06 PM User is offline

Your symptoms are common for a clutch gap issue, with the exception of the jumpered switch.

Have you verified that the switch is open when hot?

If the switch has developed a resistance across the contacts (or the connector) a voltage drop to the clutch coil could be the problem. The next time it drops out, try checking for voltage at the clutch. You can also try tapping the clutch plate to see if it will engage, but you should be very careful doing this with the 3 ears that stick out on that clutch.

Never a good idea to run with a jumpered switch without your gauges attached. You could see some extreme pressures in a hurry - that you do not know about.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

AC Amiture on Sun September 21, 2008 5:01 PM User is offline

Well what I see now is that upon engaging the engine lugs and then the switch opens. Looks like high pressure. What are most likely causes of this?

bohica2xo on Sun September 21, 2008 5:13 PM User is offline

Many things can cause high head pressures:

Blocked air path through the condensor. Dirt, bugs, mud, oil, pigeon feathers, damaged fins, grass clippings... I have seen all of thes things shut a condensor down.

Failed, weak or intermittient electric cooling fan(s). No airflow? high head pressures.

Damaged high side lines in the system. I have seen more than one Corolla with collision damage on the little high side line. Even a ham handed mechanic can crush that line on some of them changing a strut...

If it cools normally at lower ambient temps. you have a condensing problem. The best investment you can make is a set of gauges. To do any meaningful diagnosis you need both high side and low side pressures.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

tony1963 on Sun September 21, 2008 6:29 PM User is offline

I must admit that I probably changed a few compressors that just needed an air gap adjustment. By the time that you remove the unit (talking about Volvos), you might as well install a reman compressor.

-------------------------
Grove Automotive Group, Inc.

An Alabama Corporation

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