MTodd

Re: 1988 911 3.2

My Bentley manual let me down. It had too much talk about not working on the a/c and not enough about telling which lines are the low and high pressure lines/service valves.

Also, when looking at the freon level in the sight glass is it ok seeing a fluid level at the bottom of the ball with some slight foaming about every 20 seconds? Is the ball supposed to be floating?

Can anyone help me here?

Thanks in advance.

saint

Hi. The line that runs from the compressor to the condensor is the hi pressure line(discharge) and the one comming back from the evaporator is the low pressure. (suction)
Not sure why you are getting the bubbles every 20 sec. Are you getting somone else to hold the engine revs. at a steady 1500 rpm with the engine lid down when you do that?
Saint

R22tech

If you had caps on the valves- the blue one would be the suction line and the red would be the discharge line. If no caps, what compressor do you have? As for the bubbling, you may be low on freon, as the previous post said, make sure you check it with the lid closed and the engine running at 2000-2500 RPM(not 1500). The ball in the sight glass should start at the bottom and float all the way to the top as the liquid refrigerant fills the receiver! It looks like your filling a glass with lite beer! The reason the Bentley manual talks more about staying away from the a/c system than how to fix it, is because a/c theory and repair is a field of knowledge on its' own, and there is no practical way of teaching it safely and properly in just 20 pages or so of text! It took me 2 years of full time school and 5 years experience to be able to get my HVACR license and certification. I can tell you that the 911 has a complicated(read: pain inthe a$$) a/c system that even when working properly, is only marginal. Good luck and let me know if you have any more questions.

MTodd

Thanks Saint and R22Tech,

I was not running the engine any higher than idle. I will go back and try that.

My compressor is a Nipondenso (or at least that is the brand on the clutch). The caps are both black. Based on what Saint noted, it looks like the lower service valve is the low pressure one.

R22tech,
In reference to your "lite beer" analogy, should this filling up happen just once,or continuously?

I am not interested in doing any real repairs to the a/c system, but I do have some leftover R12 and a hose with a tap.

I recently had the system recharged by an "expert" and paid $55/can plus $40 labor.

I have an a/c pressure gauge (like a tire gauge) and was wanting see if I have any major leaks.

Also, when the inevitable slow leaks take me to the point of needing a recharge, I was thinking that could be a job I could handle and save a few bucks.

Is that a job a rookie should stay away from?

Thanks

R22tech

1) it should "fill up" just once while testing it.
2) price of $55 plus $40 was a good price
3) can't tell anything about leaks with a gauge other than if it leaked.
4) if you really want to do-it-yourself, buy a set of manifold gauges specific to r12 with both a high side and low side. You absolutely need to know the pressures of BOTH sides while charging your system AND for diagnosing the system! You can pick up a set at an HVAC Supply store for about $50+/-.