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AC Suddenly Stopped - Pressure/Fuses/Relays/Switches Fine

Spidey300

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Hi All, 98 2.5L 2WD XL w/ Auto Trans. On my way home from a camping trip last summer. The AC suddenly cut out and stopped blowing cold. I grabbed a recharge kit on the road but when I hooked it up it said the pressure was good and no charge was needed. I didn't mess with it at the time since it was almost fall.

Now I'm looking into it. On a trip to the salvage hard I grabbed the high and low pressure switches, relays, fuses, etc. The compressor is not engaging so I systematically swapped out each switch, fuse, relay etc. and none of that solved it so I think I can rule those out. I hooked up my AC Pro recharge kit again and it was reading 0 pressure, which I thought was odd since I could definitely hear pressure as the schrader valve engaged when disconnecting the high pressure switch. So I recharged it for about 10 seconds and when I released it was in the middle of the green but compressor clutch still not engaging and only hot air coming out.

I quickly jumpered the low pressure switch and the compressor clutch engaged but it made a bit of a screeching sound. Only jumpered it for a few seconds. About 5 years ago I had a leak in the compressor so I had it replaced, along with the accumulator/drier, orifice tube, o-rings, etc. AC was flushed and filled and worked for 5 years before the sudden cut out. I have a (I think) separate issue with AC diverting to only blow hot air out of the defrost/floor while accelerating but I think that's a separate vacuum related issue.

Anyone have any thoughts on what the issue might be?
 


Uncle Gump

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If you jump the low pressure switch and the compressor starts... the system pressure is to low or you have a bad low pressure switch.
 

RonD

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+1 ^^^^

Retest pressure in the system



The Vent door direction in the cab is indeed Vacuum operated
There is a Vacuum reservoir "ball" in the engine bay, passenger side front down low, usually in front of passenger wheel well
From the reservoir there is a black hard plastic vacuum line that runs to the firewall and enters the cab
This line can crack or melt(exhaust heat), easily repaired/spliced with rubber vacuum hose of correct size

But Vacuum reservoir can also crack or its check valve can break, so it can't hold vacuum "in reserve"
When you accelerate vacuum in the intake drops low, the vacuum reservoir is there so that won't effect cab vents


Similar to the power brake booster, its size is so it can hold vacuum in reserve, it has a check valve to hold vacuum, so if engine should stall driver will still have power assist braking to pull over and stop, usually about 3 pedal presses will use up the reserve
 

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Zero pressure at the accumulator (passenger side, low pressure) is a pretty good indication that you have a leak somewhere and my guess is that's why it just quit, it got too low for the compressor to kick on and then the rest leaked out over the course of the winter. The low pressure switch will trip somewhere around 40-50psi and if there's nothing in the system, your 10 second blast of refrigerant was probably not enough to get you there.

I would remove the low pressure switch and give the schrader valve there a little quick press to see if you have anything there at all. Should get a pretty good squirt of refrigerant coming out. That will rule out your gauge. The refill hoses/gauges that come with refill cans are pretty low quality. If you don't see much pressure when you check that, you have a leak somewhere.
 

Spidey300

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Alright, I removed the low pressure switch and pushed the Schrader valve and got nothing, so I gave it some more recharge kit and the compressor kicked on. It didnt sound great but stayed on. No cold air though and the lines didnt get cold.

I'm still mostly only getting air from the defrost vents. I swapped out the vacuum reservoir for a salvaged one and checked the line going to the firewall. It looks like it was spliced with a piece of vacuum hose in the past but seemed secure and tight.

Last summer I started putting a clamp on one of the heater hoses running to the firewall to keep it from blowing hot air all the time and overtaking the AC when it was working. By doing that the air would still cut off when accelerating hard but at least wouldn't blow hot.

What do you guys think? Not sure why it wouldn't start getting cold once it got enough refrigerant and the compressor kicked on.
 

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Just going by memory, a ‘98 would take somewhere between 28-32 oz of R134a (don’t take that as gospel, double check it). How much did you put in? It’s going to take a pretty good amount to actually get cold air out of the vents.
 

RonD

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AC cools by HEAT
One line on the compressor goes to the condenser, in front of radiator, that line should get HOT, if not then compressor is not working, or its dry, lines are plugged
Which is why it sounds funny

Compressor does what it says, compresses the "freon", and that causes it to get very hot, and it "stores energy"
When this high pressure hot fluid/gas is released thru a small valve(orifice) it releases that energy by getting VERY COLD

If you have ever had an air compressor, its the same thing, compressor gets very hot and so the the air in the tank
But when you release that compressed hot air it gets very cold when it comes out

Vehicle or home AC works the same way, its just that "freon" gets hotter so gets cooler as well, same for refrigerators and freezers, its more efficient than air



You shouldn't need to plug a heater hose
Your Blend door is not working
Temp knob controls the Blend door in the cab, the blend door COVERS the heater core to prevent air flowing thru it when knob is turned to COLD
So there should be no heat at all in the cab with knob turned to COLD
 

Spidey300

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Not sure how much was added, probably not even half of the 20oz AC Pro bottles. I stopped once the compressor kicked on and the gauge on the refill bottle was near the top of the green, but I know those gauges are crap. So maybe I added enough for the compressor to kick on but didn't add enough for it to cool?

I'll try again but I worry about messing up the compressor. Ill feel the line leaving the compressor as RonD suggested.

Ill check my blend door actuator too and see if maybe the door is broken. It looks like there are some workarounds/fixes. If AC was working before though when I clamped the heater hose but air was just cutting out when accelerating wouldnt that suggest the blend door was ok and it's a vacuum problem? With hose unclamped, AC used to work at idle but would blow hot even with system off and would cut from AC to hot from defrost and floor when accelerating.
 

snoranger

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Not sure how much was added, probably not even half of the 20oz AC Pro bottles. I stopped once the compressor kicked on and the gauge on the refill bottle was near the top of the green, but I know those gauges are crap. So maybe I added enough for the compressor to kick on but didn't add enough for it to cool?

I'll try again but I worry about messing up the compressor. Ill feel the line leaving the compressor as RonD suggested.

Ill check my blend door actuator too and see if maybe the door is broken. It looks like there are some workarounds/fixes. If AC was working before though when I clamped the heater hose but air was just cutting out when accelerating wouldnt that suggest the blend door was ok and it's a vacuum problem? With hose unclamped, AC used to work at idle but would blow hot even with system off and would cut from AC to hot from defrost and floor when accelerating.
8-10 oz may be barely enough to turn the compressor on, but it is not enough for the system to work properly. Your problem is low refrigerant.
You need to fix the leak, pull a vacuum on the system, and then refill it.
 

RonD

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Blend door is electric
If its not moving, covering Heater Core or uncovering it, then its an electrical issue in the cab, almost always the blend door motor

The Vent direction, defrost, panel, floor, is vacuum operated, defrost is the default direction, low/no vacuum = all air to defrost vent
When you accelerate vacuum in engine drops to almost 0 so......................
That's why vacuum reservoir is used
There is a Check Valve either in the reservoir or on the vacuum line that comes from the intake manifold

Can look like this, a YG360: https://i.ebayimg.com/images/g/1BUAAOSwxn1bj4rq/s-l300.jpg
 

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You simply have to put gauges on the system to diagnose it. System pressures... both high and low side are the only way I know what's happening.
 

Spidey300

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Thanks all. I checked the blend door actuator and I can feel it moving when I turn the temp selector. Today the compressor wouldnt cycle on again so I added more recharge kit. I added until it read 40 psi/yellow on 2 different recharge gauges. None of the ac lines got cold. Line out of compressor was hot and dry but not HOT hot. Sounds like I have a large leak and compressor may be bad or lines clogged.

For the vents, it started off blowing out defrost when on Max AC but when I switched to just AC the hot air would come out of the proper vents. Then switched to floor and air would come out at floor and not dash vents. Back to Max AC and it was coming out dash vents too and a little from defrost.
 

snoranger

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Thanks all. I checked the blend door actuator and I can feel it moving when I turn the temp selector. Today the compressor wouldnt cycle on again so I added more recharge kit. I added until it read 40 psi/yellow on 2 different recharge gauges. None of the ac lines got cold. Line out of compressor was hot and dry but not HOT hot. Sounds like I have a large leak and compressor may be bad or lines clogged.

For the vents, it started off blowing out defrost when on Max AC but when I switched to just AC the hot air would come out of the proper vents. Then switched to floor and air would come out at floor and not dash vents. Back to Max AC and it was coming out dash vents too and a little from defrost.
Without a high side reading, you really don’t know what’s happening.
As much as I hate to recommend Harbor Freight...
You should go buy a gauge set.
35ECDD41-AAD3-4492-82AF-407AC94887CE.jpeg
 

Spidey300

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Thanks all. I checked the blend door actuator and I can feel it moving when I turn the temp selector. Today the compressor wouldnt cycle on again so I added more recharge kit. I added until it read 40 psi/yellow on 2 different recharge gauges. None of the ac lines got cold. Line out of compressor was hot and dry but not HOT hot. Sounds like I have a large leak and compressor may be bad or lines clogged.

For the vents, it started off blowing out defrost when on Max AC but when I switched to just AC the hot air would come out of the proper vents. Then switched to floor and air would come out at floor and not dash vents. Back to Max AC and it was coming out dash vents too and a little from defrost.
And I just took it for a drive to check the redirect to defrost with WOT and it's still doing it so it seems there is still a vacuum issue somewhere. I dont have gauges or a vacuum pump so I guess I'll have to take it in for diagnosis. With all I've described, could a broken blend door still he contributing to my issue? I've heard that's pretty common but the actuator is a pain to remove and I'd hate cutting a hole in the plenum behind the glovebox to check the door of I dont have to.

Ultimately, it sounds like I have a big leak and maybe faulty compressor but fixing that wont help if the AC still cuts to hot defrost with WOT so I need to solve both.
 

Spidey300

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So, about the vacuum leak, what is this and where is this vacuum line supposed to connect?
 

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