So the ac in my new purchase doesn't work. The seller said in his ad that the compressor was new but it's actually about 15 years old. I've seen a lot of ac threads but is there a common culprit? Where should I start looking ?

Also. Installing a new radio. Any special considerations?

 

When you say it doesn't work, what happens (or doesn't happen) when you push the AC button ?
- are you certain, or do you know if, it is properly charged with refrigerant ?
- do you know if your compressor activates ?
- does your fan operate and do you have the different speeds ?

 

You have to work methodically through it to find the problem. Here is an excellent guide, courtesy of 928 Specialists and Wally Plumley.
https://www.928gt.com/T-WallyHVAC.aspx

 

Thanks guys !

 

Concur, stepwise is way to go.
One frequent failure point is relay in the HVAC control head...so it is timely that you are pulling the radio- consider sending the HVAC head out for rebuild or retrofitting relay.

 

Also, wrt radio- there are some specialized products avail if you like- the "sharkwoofer" adds some thump and one our resident owners/talents researched and produced some custom high-end replacement speakers. It's all on here...somewhere.

 

Search is your friend, tons of threads here on A/C problems.

If you take it to a shop, if all they do is vacuum, flush, refill, you may still have a leak. If they replace seals, expect hefty bill, in range of $1,000 and up.

Most helpful is Dwayne's Garage and his excellent guides, one of which will familiarize you with the system and what is going on.

Additional note on the control head relay if that is the problem: don't just replace it. It fails b/c it is not up to the task. It needs a more robust relay. Again, there is a step-by-step on adding a larger relay, a rather difficult task as the relay must be mounted external to the body of the unit, involves soldering, etc. Good luck.

http://dwaynesgarage.norcal928.org/