aggravation

I don't know how many switches are in between your comp clutch and the battery but make sure all that you have access to are on ie; AC switch, thermostat set to a cold temp etc.
Then jump the freeze switch (I'm assuming it is supposed to open on low event ie; breaks the circuit when the evap gets too much frost on it) then start bypassing each leg of the circuit that could be open, each wire from one component to the next until you find the break in the circuit.
Are there other safeties in the 928 AC circuit? maybe a High pressure switch or a loss of charge (low liquid pressure switch)?
Sorry, I know my refrigeration but never worked on automobiles other than to add some gas once in a while to my own (I'm too lazy to fix mine yet since I have refrigerant and manifold sets scattered about).

EDIT: Way to go. By the way, Double Agent is technically correct on the micron gauge but Dr.Bob's old school method of pulling a nice long vacuum will work well for you assuming there is no leak or a couple teaspoons of water in the system. I have a micron gauge on one of my trucks but I think the only time I ever used it was to teach a rookie about the general principles of vacuum...of course the other day two of my guys installed three condensing units on the roof of a restaurant and if they had used it they would have found out there was in fact a bunch of rainwater in the old line sets that the old school method didn't reveal....

largecar379

just thought----

have you flushed the entire system, before you started on vacuum and recharge?

there are kits to do this, and with a system that is, say, 20 years old.....flushing everything is a good thing.

you'd really be surprised to see how much junk---old oil, metal shavings, etc....---is in a system that has never been flushed.


something to think about.....

--Russ

Mrmerlin

did you add oil to the system/compressor? and replace all of the line O rings?

RyanPerrella

no i didnt touch the oil, left it as is.

O rings were replaced where they were opened 2 on the dryer and 4 on the expansion valve.

I left the vacuum pump run in excess of 4 hours. I also left the gauges on for 3 plus hours and when i returned they still held the 30in of vacuum.

Roger Tyson was an INVALUABLE ASSET to me in this process helping me diagnose my electrical issues (which there were none actually) He helped me step by step covering the entire AC system electronics, something i am still VERY INEXPERIENCED IN. But having now done this i am ready to tackle any AC issues that may arise with future projects and feel allot more comfortable around the electronics side of thigs as well.

THANKS ROGER!

I am now going to add refrigerant but the battery is dead from running the fan all day so thats being charged and i will charge the refrigerant either tonight or in the morning and will report on my findings.

THANKS EVERYONE THAT CONTRIBUTED!

ZEUS+

Hi Curt and welcome to the list, nice ride. Just wanted to point out that it is the refrigerant that has a chemical reaction with moisture and creates HCL acid. Heat aids this reaction.

dr bob

DoubleAgent, welcome to the group! Great advice for sure.

A micron gauge is a valuable tool if you know how good your pump is to start with. You can let the pump suck against just the gauge and manifold to find that out. If you don't have or take the time to let the pump boil all the moisture in the system, then the point is moot. Realistically, auto systems get vacuumed for minutes not hours, and we depend a whole lot on the receiver-dryer to get the last bits of moisture captured safely. For commercial systems, larger by far than a car system, a good micron gauge, a good pump that will pull down low enough to boil the water out, those are really essential.

I also appreciate the idea that pulling on the system for a long time is 'old school', but a lot of the old school physics principles still apply. One is that water boils at certain temps and pressures. More time means more water will be boiled, even if the vacuum is not quite that good. Time and some ambient heating are often all that's needed in a small system. On a hot day in Austin, there's a reasonable chance that it will be enough.

Air in the system is still the big thief of system capacity. Pump all of the air out and it will cool better.


Ryan--

The liquid charge method amazingly simple and quick. Using the compressor to 'pump' the refrigerant is OK, and probably essential if you are charging to the sight glass. Charging to weight from small cans means you know in advance how much and how many will be needed, so you can just put the right amount in to start without referring to the sight glass until all your refrigerant is introduced.

dr bob

Also--

You have no idea how much oil is in the system after you have replaved components like the drier. You can use an educated guess, based on the capacity charts numbers in the WSM, a good start. You still don't know how much left with the last few freon charges that leaked out. Top up the oil with best-guess quantities if you haven't pulled and drained the compressor. Needless to say, oil is pretty important, and the right amount is also pretty important.

RyanPerrella

really? do i have to?

I was hoping to avoid this altogether. I have no idea how much oil left the system. I also have no idea how i would reintroduce oil into the system unless u remove the compressor at which point it would make sense to simply drain all the oil and refill.

aggravation

Old school it is but it's the way it's done out in the field most of the time and with the benefit of experience to spot potential trouble you can leave the micron gauge in the box 99% of the time.

JHowell37

Just out of curiosity, what do people consider to be a "good" vacuum pump.
CFM?
Brand?

Rob Edwards

With the caveat that I don't have a micron gauge to assess how low it'll go, I bought a Robinair 15600 6 cfm pump off of Ebay for $176 plus $27 shipping last July. They say 600 microns within 60 minutes. I'm happy with it.

Here's the vendor I used:

http://cgi.ebay.com/Vacuum-Pump-Robi...QQcmdZViewItem

DoubleAgent

Thank you for setting the record strait . You are quite correct. I'm sorry if this was misleading in any way. post edited. It may not effect the system the same way it would your Home or commercial AC. More research needed on my part.

Second post...WOOHOO...Correcting first ...Crap!

have a good day guys

dr bob

There are a couple ways to get oil in to the system. One is to 'vacuum' it in from a measuring cup. System under vacuum, yellow hose end into the oil, open the high-side valve to draw the oil into the drier. Just don't suck air in, and that's tough to avoid using this method. I have a fourth hose, and pull vacuum from the port under the safety switch, so I don't have to vacuum again through the hose I just oiled.

Another is to use the oil-charge cans of refrigerant, charged the normal way. If you are using R-12, which I have to assume since you didn't change the compressor oil and do a little flushing, you'll need to find the correct mineral oil to add. The oil-charge cans for R-12 are tougher to find these days.


As much as I think that AC work is not too tough, it takes some specialized and often expensive tools to do it right. There's some tolerance for hack solutions, but the performance of the system will suffer. Witness the slew of posts a few years ago showing how one could just 'sweep' the system a few times with R-12, and no need for evacuation. Then vent temps of 55º, which the users thought was 'good enough'. My general recommendation is for folks to do the relatively easy but time-consuming mechanical parts of the projects, like replacing hoses and o-rings that leak, drain and refill the compressor with oil, etc. Then let a pro do the evac and charge with the right tools. If you are working on just on one or two cars, it's hardly worth spending $hundreds on stuff you'll use once in a blue moon.