300 TDI AC drains battery

[TexasTJ]

So I have a small electrical Grimmlin I'm trying to sort out right now. When ever I run my AC in my 300 TDI discovery it runs my battery down. The next time I go to start the truck I have to jump it. Any ideas. The AC electrical looks like it wired correctly. But I did not do the install.

Thanks. Nate.

 

[El Solis]

Is the alternator keeping up the A/C draw? Have you check for a parasitic draw when the car is off? I'm not an expert by any means but I have a 200 w a/c, the only electrical draw is when the blower and condenser fan are running I believe. So it's one of those pulling power. The alternator should keep up with that. Any issues when driving at night with the lights on?

 

[Herbie]

I would look for a short in the AC clutch or clutch relay. There's typically an AC relay, that drives a solenoid-actuated clutch on the AC compressor. If that is getting locked on, then it will continue to draw power after you shut the engine off.

Start with the relay, that's an easy check. There may even be a second relay in the engine bay that you can swap, although getting a new spare is a "safer" thing to swap out.