AC compressor starts turning on and off instantly after 10 minutes drive

[samk844]

AoA,

I have baleno 2001 model. When the car is started, the AC works perfectly and there is no such issue. After driving it for like 10 minutes the AC cooling suddenly drops. I checked the system and found out that AC compressor starts turning on and off instantly and hence fails to work and this is why the cooling drops. I turn the AC off, keep it turned off for a few minutes, then turn the AC on again... and it again works perfectly for a few minutes and then starts this behavior again and the cooling drops.

I have tried:

1. Cleaning up the radiator and AC condenser
2. AC complete service and Gas Refill
3. Replacing the Radiator Fan / Temperature sensor switch

But the issue is still there. Any ideas?

[akash190]

Check themostat sensor present on evaporator coil

[samk844]

Check themostat sensor present on evaporator coil

It seems to work fine because the AC works perfectly for the first few minutes. The compressor turns on and off almost perfectly at different time intervals at different fan speeds. Just after 10 to 15 minutes the error starts. If thermostat sensor is faulty then it should show symptoms at all times.

[akash190]

Sir there was a hiace in my town uska masla tha after ac running for good 10 minutes compressor off ho jata tha masla ye nikla ke uske sensor pe baraf jamti thi jis wja se compressor on hi nai hta tha to apka issue shayed is se related ho

[geek.maan]

Check themostat sensor present on evaporator coil

yes please! do that -- is your evaporator draining properly? not choked or so?

[samk844]

Yup... I see a lot of water coming out of the drain pipe continuously as long as AC is on...!

[capsat]

expansion valve is malfunctioning , visit your ac workshop.

[samk844]

expansion valve is malfunctioning , visit your ac workshop.

Expansion valve?? Where is it located?

I visited 2 AC workshops 3 times and the problem is still there....(First time, they just filled the gas, when it didn't work I visited 2nd time and they serviced the whole AC system and refilled it. When this still doesn't work, I visited the third time and they asked me to get radiator cleaned and serviced, which I did and the problem is still there... I have already spent more than 10K in this process..!

Oh there is 4th time as well, when I was recommended to change the radiator fan / temperature sensor switch, and the issue is still there.

[samk844]

I have posted here for suggestions, because I know that if I go to any AC workshop again, they will surely ask me to change the compressor, which will cost around 12K additionally and I know the problem will still remain there...!

[shabbir.1]

If the compressor clutch is disengaging repeatedly, it might be happening due to some electrical fault.

To diagnose, either get a clamp meter to record the current flow to the compressor clutch or get a simple multimeter/voltmeter to measure voltage right on top of the compressor, attach one probe with the metallic chasis or comoressor's body and second one to the nearest connector supplying power to the compressor.

Please ensure to take these readings as close to the conpressor as possible.
Check what happens to voltage when then comoressor disengages unexpectedly.

If the connector is absent on the wire supplying power to the compressor and wires are splice jointed, open the joint clean all the wire strands, scrub them to remove all the residue from insulation tape or other oily substance. Make a fresh joint and see if it makes any difference.
If you are getting proper voltage at this point then trace back the circuit and check the relay inside the fuse box.

If you can provide the electrical connection diagram of your car's AC, we will be able to guide you in a better way.

[akash190]

A professional electrician should sort out problem under minutes

[capsat]

if you are located in Karachi

Quick Cool at Khushal Road off Allama Iqbal Road 0321 212 7270
Sabir AC services @ Sakhi Hasan North Nazimabad 0300 2152054

[samk844]

If you can provide the electrical connection diagram of your car's AC, we will be able to guide you in a better way.

Check these!

[samk844]

if you are located in Karachi

Quick Cool at Khushal Road off Allama Iqbal Road 0321 212 7270
Sabir AC services @ Sakhi Hasan North Nazimabad 0300 2152054

I am actually in Rawalpindi.

[shabbir.1]

Check voltage on the B/Y (Black/Yellow) wire, coming out of the No.11 relay and connected with the compressor magentic clutch, when the clutch disengages unexpectedly.
Once right on top of compressor (or as much closer as possible) and second time near the No.11th relay.

If the voltage remains present when the clutch disengages then there is an issue with magentic clutch or thermal safety/cut off switch of the compressor (diagram doesn't contain it though).

If the volatge disappears during this time period then check the No. 11 relay, you may temporarily swap relays 11 and 12 to confirm their working.

If doesn't help either then check connections on the No. 7 component (AC amplifier) and thermistor attached to the evaporator unit.

[geek.maan]

Try visiting Auto Net G-9 Markaz, Islamabad. Tell the guys there Abid Sb. (Of golden cuore) sent you, they will hopefully treat you well.

[samk844]

Okay, as per your suggestions, here is what I did.

1. Bought a new multi-meter for measurements
2. Tracked voltages near compressor and relays.

The voltage was also dropping to 0 whenever the compressor tripped, whether normally or instantly (abnormally). During working time it remained at 12.5V approx continuously.

Also tried swapping the relays but there was no improvement

[shabbir.1]

From this analysis, it is now at least established that the compressor or it's magnetic clutch is ok and the problem lies on the control side of No. 11 relay.

One end of the No. 11th relay coil is attached with battery +ve terminal through fuse No. 22 and ignition switch in series and the other side of the same coil is attached with component no. 7 (AC camplifier) with the help of Bl/B wire.

Attach one probe of the voltmeter with this Bl/B (Blue/Black) wire on the connector attached to this No.7 device and second probe to any available ground point.

When the iginition switch is ON position and AC compressor is not operating there must be 12 volt present on this BL/B wire. For the compressor to operate this wire must be connected to ground i.e., voltage on this wire shall dip to zero.

Check voltage on this wire when the compressor shutts off abnormaly. This observation will give us an idea whether the problem lies in No. 7 device or one of it's input signals such as the thermistor and ECM.

[samk844]

Okay so I did the above test and it worked okay. So I tried to locate Thermistor but couldn't find it. So, I took it to an AC wala... He called an electrician and they both checked and said that system is blocked somewhere. I said I got it serviced recently so this issue shouldn't be there. But he insisted on it and removed almost half of the gas to decrease pressure but it was of no avail. Then he said the final solution is to get it serviced and refilled again.

Somehow I didn't believe him so I took it to an electrician (Butt Auto electrician in saddar), he directly checked the thermistor. He took it out and then just observed it and installed it back. I guess its position got changed during this process or some dust got removed or something like this.

But anyway, the issue went away and it started working perfectly. Now the AC makes hissing noise when compressor starts. I believe it is due to the gas, which was removed. I got it re-filled again by the same Ac wala (who removed the gas) but he didn't fill it fully because he says that the compressor is weak and doesn't work correctly on idle RPM so if he charges the system fully, the compressor may fail due to pressure. Is it okay?? Or shall I get it charged fully??

Any thoughts?

[shabbir.1]

This is really great that the root cause has been identified and rectified as well.
You followed a proper diagnostic procedure to reach the problematic area and I am sure you must have learnt a lot in this whole process.

If you are in lahore visit Punjab car ac near Ganga Ram hospital and if in Rwp/Isb contact @dani_kk.

Evacuate the system fully, change the drier/filter unit along with fresh O-rings, replenish the oil level, vacuum the system with the help of vacuum pump for 5-10 minutes at least, check for leaks and fill the system by weight.

Don't bother whether the compressor is weak or not, if it is in good health along with other important parts of the system such as the TxV, it must work perfectly.