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Old 4th July 2008, 19:46   #1
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Question AC woes and strange sound... Part 2

Ok, I thought of posting this in the other thread started by Tsk but then thought better of it as I did not want to hijack that thread.

My problems are like this

I have two different AC related probs on two separate cars. On one,
  • At times there is a khrrrr ghattt ghattt sound that comes out from the right hand side of the dash. TASS says its some "AC chamber expansion" problem. Till now they claimed to have repaired it thrice but the noise comes back sooner than later. What could this be?
  • The second problem in the other car is that all of a sudden, after it came back from the service station, it has developed a peculiar compressor kick-in problem. After a careful watch I have come to some conclusions about when this problem occurs
    • If I start the car in the morning in a cold engine and switch on the AC the compressor kicks in, nice and fine. The RPM goes up.
    • In a running car also the AC gives no problems.
    • If I stop the car on some signal or a jam and the compressor is already on it keeps running fine.
    • Problem arises if the compressor cuts off. It can not start on its own after that. It just keeps making a khar-khat sound. As if the compressor tries to kick in but fails. The RPM twitches a bit at this point.
    • The moment the car starts moving and the RPM goes up the AC again comes back on.
It almost sounds like the compressor tripping when the car is standing stationary, albeit after a run (Remember, it does not happen in a cold start). The closest I came to some point was on the Subros site. It says, and I quote

Check position of accelerator or cut off switch in 1000cc and 1300cc cars.
Improper position of accelerator cut off switch will result in tripping.

I am not sure I understood that part completely. Which accelerator is this?
So now, can someone provide me some pointers about the problems of both these cars?
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Old 4th July 2008, 20:05   #2
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Quote:
Originally Posted by Zappo View Post
  • At times there is a khrrrr ghattt ghattt sound that comes out from the right hand side of the dash. TASS says its some "AC chamber expansion" problem. Till now they claimed to have repaired it thrice but the noise comes back sooner than later. What could this be?

If its occasional i would try ruling out a screw/twig/plastic clip or something similar which gets dislodged once in a while and getting thrown around.


Quote:
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[*] If I start the car in the morning in a cold engine and switch on the AC the compressor kicks in, nice and fine. The RPM goes up.[*]In a running car also the AC gives no problems.[*]If I stop the car on some signal or a jam and the compressor is already on it keeps running fine.[*]Problem arises if the compressor cuts off. It can not start on its own after that. It just keeps making a khar-khat sound. As if the compressor tries to kick in but fails. The RPM twitches a bit at this point.[*]The moment the car starts moving and the RPM goes up the AC again comes back on.[/list][/list][indent]It almost sounds like the compressor tripping when the car is standing stationary, albeit after a run (Remember, it does not happen in a cold start).
Sounds very much like your AC radiator grill (Engine side) getting HOT = Faulty fan unit / fan circuit / Blown fuse for the circuit / or faulty connector to radiator fan.

For a sure check, let the car run on cold idle with AC on, stand outside and observe if the radiator fan switches ON in 1-2 minutes. If its not coming ON, grill temp will shoot up and AC compressor will switch off.
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Old 4th July 2008, 20:08   #3
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i guess that it may require a ECU reset as its come from service and the mechs usually dont go to disconnect the -ve. so try the ECU reset as explained by dadu on the ECU reset thread.
I guess its a throttle position sensor / the idle solenoid

btw which make model is this second car? i am guessing tata but model?

Last edited by Jr Godzilla : 4th July 2008 at 20:11.
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Old 4th July 2008, 20:20   #4
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Both are Tata. The first one is the Indica Turbo DLG and the second one is a regular Indica NA. Maybe I will start with the ECU reset then.
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Old 4th July 2008, 20:23   #5
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Before you go the ecu way, suggest you rule out the fan issue. Will take only few minutes when engine bay is cold.
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Old 4th July 2008, 20:23   #6
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Both are Tata. The first one is the Indica Turbo DLG and the second one is a regular Indica NA. Maybe I will start with the ECU reset then.
doit Dadu's method as explained
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Old 4th July 2008, 23:41   #7
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Jaggu dada,
1. In the first case, actually there is no loose bits thats making the sound. Neither is the sound that of anything metallic hitting around. Its something else altogether. Difficult to explain, maybe I will upload a small mobile video that captured the sound once. Its a gruff sounding ghatt ghatt sound. And the TASS guys very confidently say its AC chamber wall expansion or some such thing. Though it has not yet sorted itself out.

2. In the second case, ummm... if the fan was not coming on won't you say that at times the same problem will also show up in the running car. Here I presume that you are alluding to the fact that in a running car the air hits the dams and that probably helps keep the temperature down.

However do note that
* No matter how long the car keeps running the compressor never has a problem in starting. I would say in a hot day it should heat up sufficiently on constant running so as to show up even when the car is running.
* A couple of days back on a hot day I got stuck in a bad jam and was stationary for more than 2 minutes. However the compressor did not cut off at all. However once I started moving it did. And then started in a while. It kept working thus raising the faint hope that the problem has probably sorted itself out. However on the very next signal the moment I stopped the compressor cut off and then again the routine was back, till I started moving again.

My suspicion is that since there is a switch that bumps up the RPM in a stationary car (is that the accelerator that Subros is referring to?) to let the compressor run probably that has gone kaput... maybe.
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Old 5th July 2008, 00:03   #8
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2) No it wont show up in running car, i had this problem once hence am saying this. As soon as speeds crossed 20kmph for about 30 secs the compressor would come ON. I think it was even lesser, closer to 10 secs.

The switch (accelerator cut off) is to cut off the AC, for additional power in case of sudden acceleration. Thats what i have seen in Maruti vehicles. Otherwise RPM will be controlled by ECU which bumps the rpms when AC switch is ON, in a MPFI engine.
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Old 5th July 2008, 00:15   #9
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Oh ok. I need to add a few more things here. Anyways I will try your suggestion tomorrow morning in a cold engine but nonetheless, in the running car, the compressor remains on for extended periods. That I have noticed. It does not switch itself off every 10-20 seconds. In fact as I was telling you in the previous post the other day I was standing stationary in a sort of signal jam for almost 2 minutes and the AC kept running since it was already on when the car stopped.

Another thing, I have noticed that if I can time it correct, the moment the compressor tries to come back to life if I start revving in neutral the compressor starts running but if I release the accelerator and the rev falls the compressor cuts itself off. However if the rev falls when I stop (from moving) and the compressor is already running it does not happen.

What gives?

Last edited by Zappo : 5th July 2008 at 00:16.
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Old 5th July 2008, 02:44   #10
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Its called the FRCP switch or something, That goes Kharr ghat and rpm rises.
In my indica also it went kaput, twice in 100,000kms
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