AC Failure Help me understand gauge pressures?

Hoping I can get a little advice here. This is a 2000 with almost 300K miles on it probably running all the original AC equipment... I know the right move would be to basically replace everything but I don't think I'll have this truck much longer so I'm really hoping someone can help me pinpoint the issue so I can only replace what I need to.

AC has not been blowing cold at all for quite a while. I finally bought a gauge set and hooked them up, I was getting 30psi on Low Side and 25 on High. This is 80-degrees ambient, AC on full blast with truck warmed up and the clutch is engaging.

I tried adding a little R134a, it took almost nothing, maybe an ounce and the low side pressure immediately shot to 90 with the high side climbing a little but much slower. Over about 5 minutes low came down a bit to 80 and high settled at 75. I don't have a helper to rev engine but when I do and go back to the gauges there is little/no change.

From what I'm reading the compressor is probably shot? Is there a way to confirm this before ordering another? It also seems like this could be a restriction in the lines somewhere?

What would be my diagnostic steps from here, do I evacuate the system and check for blockages with compressed air or nitrogen? Order a new compressor and start there? Anything else I can try before I go that far?

 

Just checking... the magnetic clutch is being pulled in and it is spinning? Equal pressures when not running is normal, equal pressure when running is not.

I doubt highly that the expansion valve is locked full open so that leaves the compressor. AC shops will shotgun everything in order to cover their rears, unfortunatly there is no way to test an expansion valve other than put a compressor on her, evacuate and recharge. Depending on how commited you are in finding the leak you can pull vacuum through both the high and low side of the manifold set, I will pull the lines off the compressor and plug one side of the condensor, Lowes/Home depot sell tapered cork and rubber plugs and plug the line that goes on the compressor and pull a 28- 30 " vacuum shut the the compressor off and watch the vacuum gauge, if it drops you know the leak is somewhere in that half of the system, then repeat for the other half or you can do as I do, just add a 1/2 can when needed. As a preventive measure, when the system is discharged you can replace the schrader valves, just like a car tire.

 

hmmmmm

i just went thru subaru expansion valve issue
but my symptom was ice cold for 30 mins then hot for 10 mins
good compressor/good gauge readings(ac tech next door neighbor)

i found a video of exact same symptoms on a Altima and solution was expansion valve
for the the subaru.....pretty easy sits on outside of the firewall
new O-rings/dryer/E.V. and then a recharge proved to be the solution

however
appears tacoma's the EV is inside firewall
found this:

 

Yeah when I shut the truck down I don't get immediate equalization which I *think* is the classic symptom of the expansion valve failing? Sounds like a new compressor is probably unavoidable. I like the idea of testing both sides like that separately, thanks.

 

Yes the expansion valve is inside the evaporator housing but Toyota makes it VERY easy to take the housing out. The bigest problem you will have is getting service wrenches large enough to hold/counter hold the lineset nuts, this is where Harbor Freight comes in for those use once or twice in your lifetime tools.

As to your Subaru, it sure sounds like the evaporator core was icing over.

 

Don't you have to take a fair bit of the dash apart to get in there and pull the housing? I figured I would just do the engine bay stuff - compressor, drier, condenser and try to flush the evaporator and expansion valve so I didn't have to get into that. Think I'd be foolish not to do the valve too? And if I'm digging that deep should I also be ordering an evaporator?

 

No, simple job. I have a write up "titled why you shoudnt park under a tree".

 

Yup, looks like classic expansion valve issue, running long enough you may even see icing on the high side pipe which is usually too hot to touch. I have done the evaporator/expansion valve swap out its not that bad, no one mentioned this but at a minimum you need to change out the filter/dryer as well, should be done when any component in system is replaced. Some other notes, it’s illegal to vent R134 to atmosphere, go to a shop have them pull it down, then change the parts at home, bring back to shop for recharge or get a vacuum pump and service it yourself, i like to leave the vacuum pump on for at least 4 hours to make sure the all moisture is boiled out it’s humid here in Florida. If you like to tinker its a fun job.
R/

 

Thanks! This is extremely helpful. I said I wasn't going to but then I did end up ordering new condenser and compressor. Do you think at 290K I should just swap the compressor while I have the system apart, or would you just start with the valve? I could always send stuff back. I've got a good vacuum pump so I was going to go ahead and do it myself. Oh and yes new drier and o-rings for sure.

Also should I flush the evaporator and anything else I'm re-using? I've read people saying it's only necessary if the compressor detonates but I'm in Louisiana where it's humid as all hell and I know the PAG46 oil can soak up moisture so it seems worth flushing it all out and replacing with new? If so what should I flush with, do I need to go buy the flush solvent or can I just spray with brakleen or wash with acetone or something? I've got nice dry shop air to blow thru with.

 

Ok yeah that does seem easy, I'll do it. I guess it's just the heater core that's a real nightmare job

 

A 25 year old truck with almost 300,000 miles? That AC system owes you nothing, if it were me i would replace the condenser the evaporator the expansion valve the compressor and dryer, but thats me, especially the evaporator if previous owner was a smoker, once you have it out why not? I will say try to get a denso expansion valve if available. You mentioned in first post that you weren’t sure if you were keeping truck, old Tacoma's are easy to sell in south with cold AC. Flushing, they sell AC flush in auto parts stores but if IRC denatured alcohol is the choice solvent to use.Check the book but pag oil will need to be put in these components upon install, not much but like an ounce in the condenser etc away from home at the moment so dont have access to my manuals. You own a vacuum pump so you have some idea whats going on, all the parts your buying wont add up to the price of a good vacuum pump.
R/

 

Ok ok when you put it that way you've got a good point... Just had a little sticker shock at $500 in AC parts but I think I've changed my mind and going to keep the truck for at least a while so I'll probably order the evaporator. Everything else already on order and all Denso. Good to know about the denatured that saves me $30 anyway. Thanks a lot for the advice.