# p2181 and Cooling Questions



## cnfitzgerald (Aug 10, 2009)

Currently working through an issue with my wife's 2003 VW New Beetle (2.0L). 
Noted code p2181 along with p0116 -- assumed Coolant Temperature Sensor (CTS) fault. Replaced black-top stock CTS with aftermarket green-top CTS. Cleared all codes after sensor replacement.
After approximately one month, code p2181 appeared again. Upon inspection, I noted the electric cooling fans were not working properly. Both fans work when A/C is activated, but neither fan operates during normal operation when A/C is off. 
As a next step, I replaced the thermal switch (on the lower drivers side of the radiator) with an aftermarket sensor. Cleared all codes after sensor replacement. After replacing the thermal switch, I noted the fans were still not working (except when A/C is activated).
As a third step, I replaced the fan control module with a stock (VW) module. No codes were present at time of replacement. After replacing the fan control module, I noted the fans were still not working (except when A/C is activated).
As a note, the car does not overheat (though I do have my wife drive with the A/C on to keep the cooling fans running). Also, the A/C and heat work fine at all times -- this suggests water pump and thermostat are in working order (but I have not verified).
I am near the end of my DIY ability/desire here, but wanted to ask a few questions:
1) Has anyone seen an identical issue with their VW? (Based on my reading, it seems several folks have had variants of this problem). If so, what was done to resolve this issue?
2) Has anyone noted wiring issues resulting in fan problems?
3) Could this be a water pump or thermostat issue?
4) Could this be a coolant issue? (I read online that VWs are sensitive to coolant types/ratios, etc. [seems odd to me, but why not ask]).
5) Are there any recalls/campaigns for this issue?

Thanks in advance for your help.


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## FastAndFurious (Feb 2, 2002)

*Re: p2181 and Cooling Questions (cnfitzgerald)*

did you check the fuses on top of battery, one of them is for the fans and they are known to melt down and cause all kinds of problems


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## cnfitzgerald (Aug 10, 2009)

*Re: p2181 and Cooling Questions (FastAndFurious)*

FastAndFurious,
Thanks for the reply. I will check fuses tonight. From what I understand, two fuses control the fans -- one in the engine compartment (top of battery) and one in the passenger compartment.
The fans do run when the A/C is activated -- both fans run at same time. If the A/C is off, however, these fans fail to come on at any time. I would think that if a fuse was blown, the fans would not come on under any condition. However, I will check fuses to confirm.
A few follow up questions:
1) Does anyone know if there are any other sensors responsible for fan operation? From what I understand, fans are controlled by the CTS and thermal switch, and normal operation is overridden when A/C is activated.
2) Can anyone tell me which way coolant flows through these engines? Does hot coolant flow into the top of the radiator and cold coolant out the bottom, or vice-versa? 
2a) If this is a water pump failure (no coolant circulation), is it conceivable that the thermal switch never “sees” hot coolant (as the thermal switch is located at the bottom of the radiator, where coolant may be cooler)? (I doubt this, but thought I’d ask.)
Thanks for your help.


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## [email protected] (Apr 22, 2009)

*Re: p2181 and Cooling Questions (cnfitzgerald)*

If the fans come on with the AC on the fuses are fine.
There are 3 pins on the thermostatic fan switch on the rad end tank. One is supply voltage the other two are triggers for high speed and low speed on the fans. Use a small piece of wire or failing that a paper clip, remove the plug and jump the 2 different connections with the clip/wire (carefull it gets hot fast) If the fans work then, the cooling control module is fine, the fuses are fine and the fans are fine. leaving a wire issue or an issue with the plug or the Thermostatic fan switch. If the coolant behind this switch does not reach temp the switch does not close, so a blockage in the radiator could also be a less likely, however possible cause.


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## cartsd (Sep 21, 2008)

*Re: p2181 and Cooling Questions ([email protected])*

I've experienced this exact scenario while trying to repair my friend's 2003 Jetta 2.0. Initially threw p2181 code. I have replaced ECT, thermostat, and fan thermostatic switch and new VW coolant. While replacing the thermostat, I felt the water pump impeller with my finger -- feels tight, does not spin freely, so I assumed it's ok. I noted the same situation regarding the fans. They work fine with A/C on. Bypassing (jumping) the thermostatic switch causes them to come on. Both speeds work fine. HOWEVER, they NEVER come on under any circumstances when engine is up to operating temperature and A/C is off. Even after replacing the thermostatic switch. I've pondered the same question: could a faulty water pump be the culprit? I.E., could the thermostatic switch not be seeing hot enough coolant to cause the fan to come on? Wouldn't there be signs of engine overheating? (There are none, as far as I can tell). p2181 is back, BTW. I'm stumped.


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## vwtech0707 (Jan 25, 2006)

replace the thermostat and oring and that should take care of the problem. dont rely on aftermarket thermostats, i never trusted them. go and buy a oem vw thermostat.


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## cnfitzgerald (Aug 10, 2009)

*Re: p2181 and Cooling Questions (cartsd)*

** UPDATE **
I took my wife's 2003 VW New Beetle (2.0L) in to a European mechanic and had the thermostat replaced and the coolant flushed and refilled. This has resolved the issue. All fans work as they should and, after 1,500 miles, no codes have re-appeared.
A few notes:
1) The electric cooling fans seem to activate at a relatively high engine temperature (higher than I would expect). My advice: if you are diagnosing this issue, make sure the engine is plenty warm/hot before determining the fans are malfunctioning.
2) I have a feeling VWs may be sensitive to coolant types and mixtures. A while back, I had topped the car off with some "safe for any vehicle, no matter what color the coolant" antifreeze. The mechanic told me this is generally not a good practice. My advice: stick with the recommended G12 coolant.
Anyhow, I hope this helps. I will be sure to post if anything changes.
Thanks for your help.


_Modified by cnfitzgerald at 6:03 PM 10-18-2009_


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## Rockerchick (May 10, 2005)

Your mechanic is correct. Do not mix coolants. You will end up with nasty sludge in your coolant lines.


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## J.Owen (May 31, 2001)

*Re: (Rockerchick)*

yup, VW's are extremely sensitive to coolant type. Always use the real deal.


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