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autowize on Sat January 23, 2010 10:50 AM User is offline

Year: 2007
Make: Daihatus
Model: Terios
Refrigerant Type: 134a
Ambient Temp: 80
Country of Origin: Saint Lucia

Hi To all. I Have put my mind to work on this AC system but just cannot figure it out. AC only kick in at High RPM.

TRB on Sat January 23, 2010 11:08 AM User is offlineView users profile

For starters I would be sure you have the proper amount of refrigerant in the system. Check the clutch gap on the compressor. I don't show a listing for the compressor, which model is it?


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autowize on Sun January 24, 2010 9:31 AM User is offline

When the Car return I will Fine out the Compressor model. But Can the RPM Sensor be the culprit?

mk378 on Sun January 24, 2010 9:58 AM User is offline

Are you saying you need to rev the engine real high, or just raise it slightly above idle? If the compressor will readily engage at any normal rpm except idle, the idle speed may be too low. In that case the computer will not engage the compressor because it would risk stalling the engine. In a modern car this is all in the computer, there isn't a separate sensor for it. The system which bypasses the throttle plate and lets air into the engine for idling is usually the cause of a modern car idling too slow.

Edited: Sun January 24, 2010 at 9:59 AM by mk378

autowize on Sun January 24, 2010 12:00 PM User is offline

I have to rev the Real high.

mk378 on Mon January 25, 2010 3:57 PM User is offline

Consider the clutch gap then. A standard test is hitting the clutch plate to see if the clutch pulls in, but be very careful of moving parts. Measure if the clutch coil is getting power. This is all assuming it is a conventional compressor with a clutch of course.

ice-n-tropics on Mon January 25, 2010 4:53 PM User is offline

Agree w/ mk
After the clutch friction surfaces wear the air gap that exists before engagement increases. Larger air gap requires more voltage to close the gap and engage the clutch to drive the compressor shaft. Also corroded electrical terminals or ground can add resistance and lower the voltage to the clutch.
Higher engine rpm can increase the voltage to the clutch.
Some clutches can be relatively easily adjusted to reduce the air gap.
Recommend that you take a voltage reading at low and high rpm (with the A/C turned on) at the wire close to the clutch by stripping back some insulation.
Speed sensor operation:
The Hall Effect rpm sensor inside some compressors allows the actual compressor rpm to be compared to the theoretical rpm for any given engine rpm. This tells the car's brain if the clutch is slipping in order to prevent breaking the FEAD drive belt and the resulting long walk home.

Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy. How To Air Condition Your Hot Rod

Edited: Thu January 28, 2010 at 5:21 PM by ice-n-tropics

autowize on Tue January 26, 2010 11:12 AM User is offline

Thank for the Information If it work I will let u know.

NickD on Thu January 28, 2010 5:56 AM User is offline

Cute little car.

Wonder if I could fit in it.

I prefer wiring the compressor clutch coil to a variable output power supply to learn the pull in and drop out voltage. And directly activating the clutch this way with gauges installed to learn the mechanical condition of the system. If all okay, then you know it's something electrical instead of guessing.

I only use a hammer to pound nails and to knock some sense into my kids heads.

With the power supply with a built in volt and ammeter, can see what the clutch current is. As it warms up, this current should decrease, if it has shorted turns that will reduce the magnetic field on warmup, can see that too as the current will increase. This way, you know for sure the clutch is good. With that out of the way, with still problems, the bottom line is that the electrical simply applies 12V to the coil when AC is called for. Helps to have a schematic of the system so you know at a glance if it's controlled by the BCM or the PCM, so again you are not guessing. Am not a very good guesser, the other way is to tear the entire car apart and trace wires, that can be cumbersome to say the least.

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