Hi there, I have recently bought a new to me 2003 Hyundai Elantra. The previous owner ran the car while the fan belt was dead, so he blew the engine and the rad system. The mechanic I bought it from replaced it with a new(ish) motor and a brand new rad system. The car only had 102.000 KMS on it, and the new motor only has 99,000 KMS. Well the first two weeks the car was running fine, and then the power steering pump went, the mechanic took it back and repaired, showed me where the issue was no cost to me, no questions asked.

Fast forward another week and the check engine light comes on. I take it back, he hooks it up to the machine and says the CoX and 2 Co2 sensors came on, but he couldn't figure out why. He thought it was because they had gotten wet. (We had torrential down pours for 8 days straight). The engine wasn’t missing, or revving or anything weird, great gas mileage etc… so he greased them up and away I went.

Now I have noticed my stereo whether I am listening to a CD or the radio will sporadically change songs, fast forward or change stations. Sometimes the radio just rolls and rolls never landing on a station. Also as soon as I get in the car, the A/C automatically turns on. What could cause this?

Bump

Bump back!
There seems to me to be an issue with continuous battey power to accessories and stuff.
Have the mechanic double check that all the grounds were reattached when the "newer" engine was installed.
With so many things to remember, car's electrical systems are sensitive to radical fluctuations in battery voltage. If you have a redundant ground wire with a poor connection, whether due to being too loose or due to corrosion, you have a recipe for problems.
If not, your car may require an electrical expert to hands-on diagnose the fault.
***btw: is the radio/cd player original equipment or is it after-market?***

Thank you! I will have them look at the wiring as soon as I can. And yes it's the original stereo.