[R(ed)32]

It seems that in warmer weather, I'm not getting the P2181 code any more. Haven't replaced any parts or adjusted coolant level to change that. ???
Have confirmed that my low speed fans are not working. Fuses are okay, fast speed works, so I'm assuming that the low speed resistors in the fan motor assemblys are shot. (My digital volt meter has died, so no measurements there yet.)
I think this is a big problem -- on a long highway drive, I got held up in stalled traffic several times. On a 66F day, after about 10 minutes idling along, my high speed fans would energize. Plugged into the OBD computer to see what was happening and found that coolant temp was cycling between about 222F and 226F with an occasional spike to 230F. (This was with the A/C off.) Can't have that happening in hot weather! Ordered two of those power resistors that I'll mount externally to restore low speed fans.
George
p.s. At highway speeds with no fans, my coolant temp was pretty steady at about 184F.

 

[kbs3]

Re: (R(ed)32)

I am having the same code p2181. I sat at the lower woodlands park today and let my car idle. I then tried to make my fan come on? I turned on the A/c and still no fan? What tells the fans to engerize? i checked the fuse and it looks alright.

 

[R(ed)32]

Re: (kbs3)

The way I understand it --
The low speed fan will come on whenever the a/c is switched on regardless of temperature. Or it will switch on between about 198F and 206F, even if a/c is off. This is controlled by a thermoswitch.
The hi speed fan will switch on between 210F and 221F, also controlled by the thermoswitch. The fan controller deenergizes the low speed circuit when high speed is switched on.
The most probable failure you have is an open circuit in the power resistor inside each of the two fan motors. That will prevent low speed fans from running. If you are at operating temperature, and idling a while however, your high speed fans should kick in when coolant temp reaches the thermoswitch setpoint. (That's good, but, if you drive like that in hot weather, you'd better not use your a/c if you have to spend any time stopped or very slow. Some people have said that it's not good to run that a/c compressor without fan airflow around it.)
If it's the low speed resistors burned out, and you're still under warranty, get VW to replace both fans. A couple weeks ago, I used the DIY method and installed two 1 Ohm/100 watt external power resistors on an aluminum plate for a heat sink. This restores low speed fans, and it will probably last a lot longer than two new fans, believe it or not.
Finally, I have never seen any proof that the p2181 code is related to the cooling fans. Could be, but ? ? ? ? A month or two before I fixed my fans, I stopped getting the P2181. Didn't do anything to fix it. I think there's probably something not quite right about my system, but it only showed up during cold weather warmups for me.
p.s. When the fans come on in hi speed, they're plenty loud enough -- you'll hear them from inside the car. Low speed is pretty quiet -- you'll probably have to raise the hood and look to see if they're spinning.


Modified by R(ed)32 at 11:20 PM 5-28-2008

 

[kbs3]

Re: (R(ed)32)

so get this... tonight i start my car with the radiator cap off. try to see if i can burp so air bubbles. now my car fluctuates a little bit from 185-190 degrees instead of just sitting at 190 all the time. i also sat there and let it heat up to 190 and still no fans. The damn thing won't over heat either.it just idles along and stays at 190 degrees. i also saw the fans turn on with the a/c so i know at least part of the system works. i am more lost then ever. i am thinking of just getting a new time belt, metal propelled water pump and whatever else and just living with it on my credit card...

 

[R(ed)32]

Re: (kbs3)

In an earlier post I mentioned that when stalled in traffic, my actual temperature monitored via OBD went up to 230F. The dashboard temp gage needle never left 190F. That gage doesn't reflect accurate coolant temperature. It's more of an idiot light and not useful to show you what's really going on.

 

[vwemporium]

Re: (R(ed)32)

Hello
This is so true about the gage being an idiot light.
If you need help give me a call. I specialize in these cars.
I'm in Montgomery NY.
Best,
Jack
email
[email protected]

 

[kbs3]

Re: (vwemporium)

i noticed 2 things today about my car...
1. even at 190 degrees on my dummy light, there is almost no pressure in the reserve reservoir and it never boils over
2. The fans never turn on. When the a/c is active sometimes only the small fan is turning.

 

[xsp2467]

Re: (kbs3)

I noticed that my fans dont come on until the engine is at the high temp, im not exactly sure but i thought that they were suposed to go on the low setting when the a/c was on

 

[rowdyzombie]

both ac fans are to come on when ac is on.

Well, both big and small fan are supposed to go on when a/c is on (low setting). I tested mine and only small fan was on, so replaced big fan and both are working now.

 

[kbs3]

Re: both ac fans are to come on when ac is on. (rowdyzombie)

Quote, originally posted by rowdyzombie »

Well, both big and small fan are supposed to go on when a/c is on (low setting). I tested mine and only small fan was on, so replaced big fan and both are working now.

I have heard so many mixed reviews about the fan's spinning. Some say low speed setting in only the passenger side fan. Some say that both fans should spin.
I have seen both of my fans run before. Then sometimes only the small fan.
I have a new theory about the p2181 code. I noticed when i took out my last green top sensor that it has no o-ring gasket. I am curios if some of the pressure is escaping due to the fact?

 

[R(ed)32]

Re: both ac fans are to come on when ac is on. (kbs3)

both fans ALWAYS switch together. if one is running in either low or hi speed, and the other is not, the one that's not running is broke. if neither fan is running in low speed with a/c on, they're both broke.
if you're using a/c in hot weather, and your low speed fans don't run, your a/c compressor may be at risk.
if you get stalled in traffic on a hot day, and your low speed fans don't work, be very careful. if your high speed fans don't come on, you should stay in your driveway, or stay on the highway and never stop!

 

[xsp2467]

Re: both ac fans are to come on when ac is on. (R(ed)32)

Thats good to know, ill have to get the vag com and heat test the car and graph the warm up process and log when the fans come on. As for the o-ring, I just replaced the greeen sensor with another green sensor, both of the sensors had their o-rings.

 

[Mike Solo]

Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)

Back from the dead. I threw this code a few weeks ago, driving down the freeway at about 70 mph.
Cooling fans are working properly.
Water pump is functioning properly.
Green-top coolant sensor installed.
If there is nothing else to check, I'll flush the coolant & replace the thermostat, and hope that covers it. Just wondering if anyone found anything else.

 

[jimix]

Re: P2181 - performance malfunction in cooling system... HELP! (Mike Solo)

Quote, originally posted by Mike Solo »

... If there is nothing else to check, I'll flush the coolant & replace the thermostat, and hope that covers it. Just wondering if anyone found anything else.

Did flushing the coolant work for you?
I've got this code too. Have already replaced the sensor 3 times, thermostat, and water pump.

 

[sveda]

Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)

Mine started this last spring on cold mornings, after doing 70 mph on the highway for a few minutes I get a CEL. Error code P2181.
Errors went away over the warm summer months, but came back in the cool fall weather. I parked the car for most of the winter, but I'm still getting Error code P2181. Coolant topped off, lots of heater output, no overheating, fans working, new coolant temp sensor...
Any insight is greatly appreciated.

 

[imcginnis]

You should check the freeze frame data for when the fault is setting, instead of just throwing every part in the cooling system at it.

 

[BillR123]

A problem with the probe sensors in the coolant tank IS a sensitivity to the coolant fluid's electrical resistance (Ohms) and if not just right, your car will throw P2181 codes. As has been stated, don't use an excess of antifreeze (as suggested, 60% water and 40% antifreeze is a good mix). Also don't use "purified" water, use only the stuff that comes out of the water hose and hopefully there's enough mineral content in your water to maintain an operating fluid resistance level.

As suggested, check your coolant mix ... you might have too much coolant ... my 2003 Audi TT had too much antifreeze at 35K miles. If someone added "purified" water to your coolant mix, then you're really screwed.

If your handy with a digital voltmeter, measure the before and after resistance of the coolant tank solution at the tanks connector ... with the cable connector removed. Hopefully note a lower resistance.

And if your P2181 codes occur at specific street locations, that's because a nearby radio transmitting device is affecting the coolant tank sensing circuitry. Radio signals are introducing a signal voltage on the coolant probe cable going to the ECU. So the solution to the problem is (1) use more water with minerals, (2) use less antifreeze, (3) use a grounded, braided shield over the sensing wire.

Application of silicone insulating grease on the coolant tank's probe connector pins would help with this "dry" circuit. "Dry" circuit refers to a circuit with very little electrical current, causing connector contacts to become more easily contaminated. Therefore, not assuring a good, electrical contact for "dry" circuit conditions.

 

[Barn01]

Great 1st post BillR123

I have been plagued with this error on and off for the past 6 months and had the water pump changed (with timing belt), and the sensor. When I go back in time I did go to mr Lube and have them change the fluid. I remember they put in the green stuff and flushed out the high mileage red stuff. I told the dealer and they said that's fine. It was shortly after this fluid change I recall that the problem with my CEL and coolant gauge dropping to C, yet it still blew hot air even at -30C outside.

I was just about to pay and have the tstat changed but I think I'm better off to change the conductivity of the coolant. Do you know approx the value I should read off the sensor? Also what kind of tolerance in that value I might have?

 

[steveppd]

First check ECT sensor resistance, if its within spec let car cold soak then take on test drive. Use your scan tool to monitor temperature and check to see if the car gets up to 175ish degrees within a few minutes. Average speed must be over 6mph to trip the light so keep it up over that. If car is to slow to reach operating temperature, 2181 will set. 99% of the time its been the thermostat.



Resistance should be between

Min Ohms Max Ohms Temp F
5000 6500 32
1500 2000 86
500 650 140
275 375 176
200 300 194

Trouble code 18613 (P2181) indicates the cooling system is not reaching operating temperature quickly enough.

1. With the engine at 68 degrees F. under normal driving conditions 175 degrees F or more should be indicated after about 4 to 5 minutes of driving.

2. If the engine is not reaching operating temperature quickly enough, a faulty thermostat is usually the cause of the slow warm up condition.

3. Check for poor or corroded connections at the Coolant Temperature Sensor (CTS) as well.

I hope this helps.

 

[jedi kyle]

i hate this light as well

i have just replaced the sensor with the green one and when i bought the car i had to replace the radiator fan. and i also replaced the coolant res. not because i thought it would have been a problem but it broke.
i have a VF stage 2 super charger on the car i don't think that should have any problem. i find the problem only comes with cold starts or if you don't let it idle for at least 5 mins in the morning. i know its inconvenient.but you should do it every day any way.