225 TT running hot
09-07-2018, 02:16 PM
#1
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225 TT running hot
Hey there, wondering if someone can help me. As the title says, I have a TT 225, but when I drive it in decently hot weather (that's like 75+ in Colorado) the car starts to run hot after idling for a bit. If I kick on AC, it slowly cools it down. I checked the fuses on the battery, and all are fine. Coolant also is fine. If someone can help me I like to enjoy my car and with this always being there I feel like I can't. Thank you😊
09-07-2018, 03:35 PM
#2
AudiWorld Super User
75 isn't warm...
Beyond that, I assume the tt is the same setup as the A4, i.e. it has 2 fans, one that is a "cooling" fan and one is an "A/C" fan. Sounds like your cooling fan has failed, so when sitting at idle, there is no air going over the radiator. When you kick the A/C on, that fan turns on and blows air over the radiator.
Anyone else have thoughts?
Beyond that, I assume the tt is the same setup as the A4, i.e. it has 2 fans, one that is a "cooling" fan and one is an "A/C" fan. Sounds like your cooling fan has failed, so when sitting at idle, there is no air going over the radiator. When you kick the A/C on, that fan turns on and blows air over the radiator.
Anyone else have thoughts?
09-08-2018, 10:56 AM
#4
It is a pretty complicated system. Over the years I have replaced fans, coolant fan control modules, thermostats and water pumps. Knowing which is the problem can be challenging.
The fans have two speeds. Sometimes low will fail and only high will work. ( a resistor in the motor fails). With AC off, the fans are turned on low by a thermo switch that is mounted on the radiator tank. ( drivers side) They seem to come on at about 100C. The switch will also switch the fans on high if radiator temp is high enough. If AC is on, the coolant control module ( under the battery) overrides the thermo switch and both fans run. They run on low until the thermo switch makes on temp and then they run on high. Note that the thermo switch is in the radiator and the temperature it sees is not the same as that seen by the coolant sensor for the dash gauge and for block 49 in the HVAC hidden diagnostic screen. The thermo switch depends on flow of the hot coolant to the radiator. A bad water pump or thermostat can produce overheating without fans running because the radiator is still cool.
The fact that your car cools when AC is on points to fan controls. Thermo switch or fan control module.
The fans have two speeds. Sometimes low will fail and only high will work. ( a resistor in the motor fails). With AC off, the fans are turned on low by a thermo switch that is mounted on the radiator tank. ( drivers side) They seem to come on at about 100C. The switch will also switch the fans on high if radiator temp is high enough. If AC is on, the coolant control module ( under the battery) overrides the thermo switch and both fans run. They run on low until the thermo switch makes on temp and then they run on high. Note that the thermo switch is in the radiator and the temperature it sees is not the same as that seen by the coolant sensor for the dash gauge and for block 49 in the HVAC hidden diagnostic screen. The thermo switch depends on flow of the hot coolant to the radiator. A bad water pump or thermostat can produce overheating without fans running because the radiator is still cool.
The fact that your car cools when AC is on points to fan controls. Thermo switch or fan control module.
09-08-2018, 02:51 PM
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