Mechanic Bypassed ECU and placed a Thermostat instead :( ... HELP!

[darthvord]

My car is an 06' Chevy Optra 1.6 LS Wagon (Automatic). Last year na notice ko na nawawalan ng lamig yung kotse at humihina yung hangin. So I thought that it might be because it's dirty already. SO, I took it to the shop and the mechanic said that my compressor clutch is not disengaging and that's why its ice-ing up. He said that everything was OK, no leaks and the system is is clean except for clutch problem. The mechanic said that it might be the ECU acting up, he suggested that we add a thermostat and bypass the ECU.

Not being a car nut (and fearing that I'd be buying a new ECU... which will cost me most of my limbs) I asked him to go ahead with the procedure. It worked, the compressor disengages automatically and it doesn't ice up anymore. Problem solved!

Or I thought it was. After a few months, I am now noticing quite a significant power loss everytime the compressor kicks in and a faint "gurgle" when the car is in idle and below 1K rpm. And also sometimes the compressor won't turn on (turing the AC switch on and off after a few minutes solves this issue... pretty annoying)

I've read somewhere that my car automatically cuts off the compressor if it detects that its under load (climbing a hill, overtaking, etc.) and knowing that we've just bypassed the ECU, I might be placing too much stress on my engine because of this. I now want to take it to another AC shop and remove the thermostat, and have it wired the way it was before.

My question now is What could be the cause of the compressor not disengaging? What should I look for and what should I tell the mechanic?

Thanks a lot in advance, and sorry for the eyestrain.

[shadow]

your electronic thermostat is busted, ang ginawa ng mechanic eh pinalitan ng manual thermostat...

[darthvord]

your electronic thermostat is busted, ang ginawa ng mechanic eh pinalitan ng manual thermostat...

So, walang sira or hindi sya related sa ECU ko and will it solve the engine problem? And magkano kaya yung electronic thermostat? Ayoko ma loko ulit, hindi kasi ako ganung ka runong with regards to technical stuff sa mga kotse. Thanks sir for the prompt reply.

[yapoy86]

for me, manual thermostat is better than the electronic sensor. electronic thermostat is just a thermal resistor that varies the resistance relative to temperature.. most of these sensor maintains a -5degree temperature (cooling coil temp) that is why your compressor works longer to achieve the -5 degree temp. this will be the cause of ice formation on your cooling coil. your sudden low engine power might be the compressor engaging while driving unlike before that your compressor is always engaged..

[fourtheboys96]

just turn off the aircon during steep climbs. it won't take too much effort doing that.

[darthvord]

for me, manual thermostat is better than the electronic sensor. electronic thermostat is just a thermal resistor that varies the resistance relative to temperature.. most of these sensor maintains a -5degree temperature (cooling coil temp) that is why your compressor works longer to achieve the -5 degree temp. this will be the cause of ice formation on your cooling coil. your sudden low engine power might be the compressor engaging while driving unlike before that your compressor is always engaged..

So sir, this is normal and is better than buying and putting an electronic thermostat back on? I've had cars before that have manual thermostats but it never takes that much power away from the engine and will it have any direct effect on the engine? The car BTW is only at 65K on the odo (home - office daily driver) Thanks!

[yapoy86]

yung suzuki wagonR ko with k10a engine pag medyo na sense nung ECU na hirap yung makina tapos nag press ka pa ng pedal automatic nag disengage yung compressor even though na nag convert na ako sa manual thermostat....

bottomline your car's ecu still have the control over your compressor and not your thermostat

[darthvord]

just turn off the aircon during steep climbs. it won't take too much effort doing that.

That's what I'm actually doing.

But problem is, when I turn it off it sometimes doesn't turn back on. The cabin gets warm pretty quick and I have to roll the windows down... and that's not really safe especially when you're driving at night and on a dark shady place with your family.

[Ry_Tower]

That's what I'm actually doing.

But problem is, when I turn it off it sometimes doesn't turn back on. The cabin gets warm pretty quick and I have to roll the windows down... and that's not really safe especially when you're driving at night and on a dark shady place with your family.

Parang may problem na sa aircon system mo sir. Baka busted na ang expansion valve mo.

[darthvord]

yung suzuki wagonR ko with k10a engine pag medyo na sense nung ECU na hirap yung makina tapos nag press ka pa ng pedal automatic nag disengage yung compressor even though na nag convert na ako sa manual thermostat....

bottomline your car's ecu still have the control over your compressor and not your thermostat

Hi thanks sir, I'll try this out. I usually just hit the thermostat switch kapag hirap. The engine rarely goes above 3K even when climbing even with the AC on, and I'm really not heavy footed on the gas.

[darthvord]

Parang may problem na sa aircon system mo sir. Baka busted na ang expansion valve mo.

Ah... cge sir I'll have that checked too this weekend. I'm trying to list down the things I need checked. Mahirap na at baka maloko nanaman ako. So so far I have 2 things na:

1. Electronic Thermostat
2. Expansion Valve

Thanks guys for feedbacks! My wife is going to give birth this month so any unnecessary gastos sa fix this weekend will be a big help for us.

[shadow]

If you open your A/C system palitan mo na rin ng drier..

[darthvord]

If you open your A/C system palitan mo na rin ng drier..

Drier: will check it out. Thanks!

[yapoy86]

pa check mo muna yung switch!!

[shadow]

I think you can only buy electronic thermostat sa casa...ok naman manual thermostat dahil a very cheap replacement but just make sure na walang problema sa system

[darthvord]

pa check mo muna yung switch!!

Sir, yung electronic thermostat ba nakakabit yung sinasabi nyo?

I think you can only buy electronic thermostat sa casa...ok naman manual thermostat dahil a very cheap replacement but just make sure na walang problema sa system

Ok sir. Naka manual T-stat na siya ngayun. So, yung erratic na pag off yung ipapa ayus ko na lang and also yung ibang parts na din like yung drier and valve.

Thanks sa mga nag reply, you guys rock!

[oj88]

Forget the workarounds and have it fixed back to OEM spec. That means, remove all previously-installed non-factory parts and have the ECU checked if it's actually defective or not.... Once and for all. Do this before you decide to overhaul the whole A/C system. It's icing, you said, so chances are there's nothing wrong with the actual A/C parts but just certain components that controls its on/off cycle.

The intermittent lack of power may be attributed to the hack. In a fully-functional car with the ECU in control, it knows exactly when the compressor is engaged and it would in turn increase power to the engine to compensate for the drag. With the ECU bypassed, your operating the compressor independent of the ECU's decision, so it may not be compensating for the power loss when the analog thermostat commands the compressor to engage.

[t2erns]

tama, ibalik sa dating set-up ang ac mo (esp kung ATC). have it checked by qualified tech or sa casa. the ac system is controlled by computer, the computer must know that you want the ac on para ma adjust nya and engine speed mo before turning on the compressor. when operating at wot (wide open throttle. the computer will automatically cut the compressor operations), also pag mataas head pressure i cut din ng computer ang ac. yung icing ay madaming pwedeng maging cause; pwede ding sira ang low pressure cut-off switch, undercharge, madumi,wiring papuntang ac relay, etc.

[yapoy86]

kung may separate switch yan A/C mo yun muna pa check mo... secondary switch lang kasi yung thermostat... as i have said sa setup ng kotse ko.. kahit naka manual t-stat ako eh controlled pa din ng ECU yung A/C... although i have a separate switch for the A/C the relay for the compressor is still controlled by the ECU so pag na sense nung ECU na nahihirapan yung engine ko momentarily switch-off nya yung A/C to allow the engine build up power...

also have the pressure switch (located sa drier or near the drier) checked... nag ice yan A/C mo kasi hindi nag automatic cut off yung compressor plus madumi na yung cooling coil mo kaya nag stay yung tubig in between the fins na nag ice kapag sobra na lamig... actually pag nag ice yan mawawala ang lamig sa air vents kasi na block nung ice yung daanan ng hangin

[jick.cejoco]

My car is an 06' Chevy Optra 1.6 LS Wagon (Automatic). Last year na notice ko na nawawalan ng lamig yung kotse at humihina yung hangin. So I thought that it might be because it's dirty already. SO, I took it to the shop and the mechanic said that my compressor clutch is not disengaging and that's why its ice-ing up. He said that everything was OK, no leaks and the system is is clean except for clutch problem. The mechanic said that it might be the ECU acting up, he suggested that we add a thermostat and bypass the ECU.

Not being a car nut (and fearing that I'd be buying a new ECU... which will cost me most of my limbs) I asked him to go ahead with the procedure. It worked, the compressor disengages automatically and it doesn't ice up anymore. Problem solved!

Or I thought it was. After a few months, I am now noticing quite a significant power loss everytime the compressor kicks in and a faint "gurgle" when the car is in idle and below 1K rpm. And also sometimes the compressor won't turn on (turing the AC switch on and off after a few minutes solves this issue... pretty annoying)

I've read somewhere that my car automatically cuts off the compressor if it detects that its under load (climbing a hill, overtaking, etc.) and knowing that we've just bypassed the ECU, I might be placing too much stress on my engine because of this. I now want to take it to another AC shop and remove the thermostat, and have it wired the way it was before.

My question now is What could be the cause of the compressor not disengaging? What should I look for and what should I tell the mechanic?

Thanks a lot in advance, and sorry for the eyestrain.

assuming your refrigerant quantity and pressure are within specs, check your vent registers for correct airflow/delivery, usually, this is done with a manometer (comparing your airflow with a known good car of the same make and model). if the airflow is low, the result is freezing of the evaporator core and of course further reduces the airflow across it. this climate control system (your computer controlled airconditioning) uses a pressure transducer installed in the low pressure side plumbing. it has three wires: PINK-low reference, LIGHT BLUE- 5 volt reference voltage, DARK GREEN (DOHC)-pressure signal or PURPLE(SOHC)- pressure signal. have this transducer checked first. this climate control is also sensitive to antifreeze/coolant amount in the system, if it is low, the climate control operates erratically too