I have an A/C problem for my 2000S40.The RPM will rave to around 3000rpm when the A/C is switched on and after will slowly return back to normal (1000 rpm).It always happens when the A/C thermostat starts to regulate the cabin air temperature (i can hear a 'bong' sound)and with just a light tab on the accelerator the RPM will rave to around 3000rpm (which should not be).Sometimes the RPM will even rave by its own without tapping the accelerator pedal.During hot climate driving is even worse thecar becomes jerky becos of the surge of the rpm and even lost of power.When i release the accelerator pedal when driving the car still moves forward becos the rpm stays at it's last position i.e 2500 rpm.immediately when i switch off the aircon the rpm goes back to normal.In the car i can hear hissing sound for about 5-10 secs when the aircon is switched on and this symthoms repeats.Pollen filters,and idling valve changed,AC gas charged but still persist. PLS Help!!!!! or ADVISE!!!!.

 

Do you have a check engine light on?

The coolant temp sensor or thermostat could be bad.

 

Hi Tech,
thanks for the reply!There's no check engine light on.Why could it be the coolant sensor faulty?If is the thermostat sensor is it costly to have it check or replaced.BTW where is the thermostat sensor located.Is it easy to change it myself?

Thanks!!

Voliic

 

When the coolant temp sensor usually goes bad it messes with the idle of the car. Espically when the A/C is on. Sometimes it will also stop the A/C from working.

Follow the top hose from the Radiator to the engine. There is a metal plate/thermostat housing that bolts to the top of the engine. The sensor is under there. But I would do the sensor and thermostat.
Once the housing is off the sensor is easy to get to.

You might want to try to have the codes pulled and see if there are any. Eventhough the light isn't on.

 

Hi Tech.
I've been to Volvo agent to have it check before.The problem was no fault code detected.And the guy told me is a might be a faulty idling v/v.Got it changed but still persist.I'll try to locate the sensors and see if i can clean up any related connectors or get it replaced.Any idea how much will the coolant and thermostat sensors cost?

Thanks!

Vollic

 

Sorry I usually don't deal with the pricing. I just work in the shop on the cars.

Look in the general section there is a post with LINKS TO SITES. Search some of the sites for the parts and prices.

 

a outside volvo mechanic said hed do it for 380$, and he told me that volvo would have charged double that ....

 

I just changed out my coolant sensor and thermostat myself, parts under $60. My source for Volvo parts is voluparts.com

 

I've traced the top hose to the hose end which is the flange/plate mounted to the engine with 2 bolts,and there is something at the side which has a bit of gold colour on it (is that the coolant sensor or thermostat sensor)?It has a wire on it and it is connected to a connector which continues to run all the way to the throttle control body I THINK.
Btw may i know how many thermostat sensors are there?Is it one for the coolant(radiator) and 1 for the aircon system? or just 1?
Thanks!

Vollic

 

Hi Sherry,

Is it your car has similar problem like mine as well?If yes, did it solve the problem after replacing the coolant sensor and thermostat sensor.
Mind sharing your experience?
Cheers!

Vollic

 

The connector with a air is the coolant sensor. When you remove the two bolts you will find the thermastat

 

I had noticed a exhaust smell - mixture not right. Then on humid mornings the car cranked & cranked sometimes. I also noticed my heat was taking longer. I read up and found out that if your temp gauge on the dash arrives to the 3 o'clock position it is the coolant sensor. And when I took out my thermostat I found that the seal had a split in it. My car now starts up first time.

 

Yes that is the coolant temp sensor. There is only one.

 

Is the coolant sensor is faulty if the temp gage hits to 3 o'clock position?
I tot if the indicator is at that position is normal!

Vollic

 

The 3 o'clock is normal but if it goes up to hot an then comes down and messes up most likely the sensor.

I had one today the guage was in the red. But the engine was running at normal temp. Then the guage was reading normal for about 5 minutes. Then went back to hot.

 

Could it be problems from the AC systems itself that lead to the erratic RPM?Becos the temp gage on my dash board always indicates at 3 o'clock postion after engine heats up and there is no signs of erratic temp increasing.
Any idea or advise..........

vollic

 

With regards to the previous mail.I've tried VOLUPARTS.com and have send mail to them to enquire for the thermostat + gasket and coolant sensor and price,but no reply yet.I've also tried other sites but seems like i find more thermostat parts rather than coolant sensor.
My engine specs is a B4164 1.6.Any recommendations?

Vollic

 

Check here:
www.myswedishparts.com

or could try on eBay for the thermostat
cgi.ebay.com/ebaymotors/87c-Thermostat-Volvo-C70-S40-S60-S70-V70-XC70-850-960_W0QQcmdZViewItemQQcategoryZ33603QQitemZ8050632 522QQrdZ1

 

Hi Tech and guys out there,
Have a question to ask you guys.Today i open the bonnet with the engine started and A/C switched on.The A/C air to cabin was good.But as usual i have the erratic RPM sympthoms.I had a look at the engine bay and i can hear a "Thok" sound coming from and near the coolant sensor electrical connector area.This is the sound that i can hear when i'm in the car.The sound comes on like every 20 secs and off and on again.And always when this happens the engine seems like loosing power.And also i can see the radiator fan turning on and off.
Pls advise from your experience.Thanks once again.

Vollic

 

Do you know what the A/C compressor looks like?
If so look at it and see if the clicking is coming from the compressor.
What temp and fan speed do you have the switches inside the car set to?
What is the temp outside?