Q: Hi Mark I have an audi a4 2005 1.8 quattro AC seems to cut out in real hot tempratures also the transmission goes into limp mode

asked by on October 03, 2017

I have 2 known problems AC automatically cuts out on very hot days it goes into econ mode by itself Transmission goes into limp mode at times when I go in reverse (not always like once every 3 or four times)

Trying to get an idea of the repair costs to determine if its worth keeping

My car has 144000 miles.
My car has an automatic transmission.

A possibility with the A/C system is a fault in the evaporator that causes internal and/or external icing. The resulting high head pressure causes the control circuitry to "throttle" the compressor, hence the ECON mode. Check for a blocked air filter and or blockages in the ducting to the evaporator. Any other cause of high head pressure, such as a blocked condenser or inadequate airflow over the condenser, can cause this as well. If there are no obvious external blockages, schedule an a/c diagnostic and the responding certified mechanic will resolve this. There are no widespread reports of limp mode via the route you describe. The first thing to check for are any stored OBD-II trouble codes that might provide clues. I would first look for a fault with external controls including the possibility of a bad wiring harness connection or a missing ground connection. There are engine controls, too, that can cause limp mode to set and those have to be checked. These include the manifold absolute pressure (MAP) sensor and the throttle position (TP) sensor. To resolve this problem you are having, the service to request is a shift diagnostic - limp mode. If you request that service the responding certified mechanic will come right to your location and get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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