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No pressure reading, compressor clutch is engaged

hardbody on Sat July 28, 2012 4:18 PM User is offline

Year: 1990
Make: Nissan
Model: Sentra
Refrigerant Type: R-134

I picked up one of those freon cans with the gauge on it and just connected it to the low side fitting on my sentra to see what the gauge would say, AC on, compressor clutch is engaged, no reading at all on the gauge. What does this mean? If the AC was low on freon enough so the gauge gave no reading wouldn't the compressor clutch not be engaged? My sentra has a conversion adapter on the low side.

I also connected the hoes to the low side on my pathfinder and the gauge did show a reading so I know the gauge works.

buickwagon on Sat July 28, 2012 4:34 PM User is offline

It may mean that the connector is not quite depressing the Schrader valve stem. Make sure the adapter is screwed on fully.

I've saved hundreds on service by spending thousands on tools.

JJM on Sat July 28, 2012 4:35 PM User is offline

Probably not the best of retrofit adapters, or they were installed wrong... which is probably a good thing because the last thing you want to do is use one of those kits to service your system... unless you're goal is to destroy the system and end up doing a firewall forward replacement of components.


When considering your next auto A/C purchase, please consider the site that supports you:

hardbody on Sun July 29, 2012 1:10 AM User is offline

I'll check the adapter tomorrow but it should be on fine, I've had my AC re-done every year for the last couple using the same adapter and my guy never has a problem.

hardbody on Sun July 29, 2012 3:09 PM User is offline

So can someone explain this to me please,

With the car off I checked the pressure on the low side and the gauge gives a reading, when I start the car, AC on I get no reading??

mk378 on Mon July 30, 2012 11:50 AM User is offline

You need to also measure the high side to know what is going on.

Also if it needs to be "re-done" every year, there is a leak.

JJM on Mon July 30, 2012 8:26 PM User is offline

This is why you can't properly charge a system with one of those silly kits. You might not be getting a reading with compressor engaged because the system is severely low on charge - which also means it likely is very low on oil, and I'm sure you know what will happen if there's no oil - the expansion valve could be defective or plugged, and if plugged there are likely other issues.

Apparently, you don't want to take the advice given here and just want an easy fix. We'll only advise the proper way to do repairs to avoid destroying your system, so good luck with the easy fix in a can.


When considering your next auto A/C purchase, please consider the site that supports you:

hardbody on Mon July 30, 2012 8:52 PM User is offline

I was not trying to charge my system, I just wanted to see what the gauge read. I bought the can with the gauge on it for someone else.

I don't think anything I posted indicates I am looking for an "easy fix" don't assume because I said I bought the can with the gauge that I was using it myself. Actually I am currently looking into buying a set of gauges (possibly from this site) and was going to start a new post on here asking if anyone could recommend a book or something that I could read. I want to learn how to do my own repairs, the right way, and may start to buy my own equipment. My guy that usually does my AC work is MIA, no idea where he is or if he is even still working on cars and I don't trust the local shops around here.

I'm pretty sure I need a new compressor since the one I have now was a cheap E-bay one and I doubt I have a leak because my guy always pulls a vacuum on the system and it never looses the vacuum or pressure (what ever it is), last time I had the compressor replaced I had my guy flush out everything and I was there watching him. The compressor I have now was pre-filled with oil, the correct type I have no idea, and it started making noises not long after I had it installed. I always replace the expansion valve and drier when ever I replace the compressor.

so please don't write me off, I'm trying to learn and soon I will have proper tools. Thanks

efxengr on Mon July 30, 2012 10:07 PM User is offline

I cant tell you how much success I have with this kit.....

If you dont want to get the whole kit I recommend the gauges in the kit and the book. You need to at least see high AND low pressures. The leak detection kit works really well but I have also used soap and bubble method to find some difficult leaks. If you read the diagnostics in the book another very useful tool is the infrared thermometer found here at AMA (with dial thermometer included). Using an infrared thermometer to check upstream/downstream temps on the condenser, evap, hoses, etc., tells you a lot. The book is good...if you want to get more indepth Haynes makes a more detailed manual. I have saved big bucks on my personal and fleet vehicles. I've also been able to help some folks out in this Florida heat who couldnt otherwise afford it (they let me experiment on their system). Post the data here and the folks will be very helpful.

hardbody on Mon July 30, 2012 10:47 PM User is offline

To clarify why I bought the gauge on the can, it's for my step daughter who has no money or job, I'm kinda pissed at her right now and am only doing little things for her, I wouldn't do anything for her if it was my choice but she has a 5 year old and my wife doesn't like the idea of her driving around with her grand daughter in the car with no AC. I can't afford to take the car anywhere nor am I going to. I can't even get my sentra's AC running at this time so not gonna spend a bunch of money to get her AC working. So the can with the gauge will be good enough for her car. Her AC was working one day the next it wasn't no idea what is wrong, she took it to someone who told her it was low on freon, I have no idea I haven't checked it.

I saw the kit you bought I can't afford to spend that much right now that's why I'm just looking for the gauges first. I know I can get a cheap set from HarborFreight but I like to have something that is going to last, I don't need the best out there but once I learn about this (AC) I may help friends out if/when they need it.

Where in Florida are you? Maybe if your close you can fix mine.

The book you have it came with the kit? Can I buy it here separately?

efxengr on Tue July 31, 2012 12:06 AM User is offline

LOL, I won't be able to make it down to Miami.....The book came with the kit but is available here along with the individual tools at
Its pricier than the Haynes but much more current....either book will get you started. We had a set of the HF gauges, they were okay for a while but inaccurate and the built in hose valves would hang up and also the platic knobs broke then fell off. For under a hundred bucks you can get Mastercool (quality) with metal handles, better guages, and they will last much longer. Its a starting point for shopping. good luck!

hardbody on Tue July 31, 2012 4:38 AM User is offline

Thanks, I saw the book was available separately after I replied. I'm near Orlando. I'll probably pick up one of the books so I have something to read and study. Thanks for your replies.

Dougflas on Tue July 31, 2012 10:43 AM User is offline

I'm located outside of Inverness if you'd like to venture over. I would be happy to help your grand daughter out. I should have service info for that vehicle.

hardbody on Sun August 12, 2012 4:15 PM User is offline

Dougflas, thanks for the offer. I checked her car today and GOOD NEWS it is now working. It seems someone's big feet knocked the rod off under the dash that moves when the hot/cold knob is turned. I was wondering why the one metal line under the hood was so cold but hot air was coming out of the vents. I looked under the dash and saw that metal rod hanging on one end and turned the white part and the air came out cold, than I went to get a flash light and looked under the dash again and saw where the end of the rod was supposed to go, hooked it back up and turned the hot/cold knob and watched the actuator move that white piece. So even though the knob was on cold the vent part under the dash was on hot. Done.

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