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AC cutting out at speed.


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stud858
Novice

Mar 20, 2018, 3:39 AM

Post #1 of 14 (820 views)
AC cutting out at speed. Sign In

Toyota vios.2003
Idling AC works fine.
Drive 10 minutes and it cuts out. Turn off and wait a few minutes
It comes back.
Had a shop check PSI. Low 50. High 300.
They said too high and released some gas and cleaned condensor.
PSI now 35 250. Same problem.
Expansion valve suspected. What else could it be. If valve it would clog at idle too, right?
I don't want to spend money on valve without eliminating other things like switches, sensors, belts, etc.


Discretesignals
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Mar 20, 2018, 4:16 AM

Post #2 of 14 (799 views)
Re: AC cutting out at speed. Sign In

Was there any work done prior to the problem? You stated that the shop released some gas. Did they release it into the atmosphere or did they recover it with a machine? It's important that the AC system has the correct charge weight. You cannot charge an automotive AC system by using system pressures.

The system needs to be recovered and vacuumed. Then charge to the correct weight and see if that solves your issue.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
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Mar 20, 2018, 6:03 AM

Post #3 of 14 (785 views)
Re: AC cutting out at speed. Sign In

This is definitely not an expansion valve problem. Follow DS's instructions first and see what you have then. If the pressures are still that high, then you should to look at the condenser and condenser fan for correct operation.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



stud858
Novice

Mar 20, 2018, 8:06 AM

Post #4 of 14 (767 views)
Re: AC cutting out at speed. Sign In

Thanks so much for your input guys In Thailand everyone releases gas to atmosphere. No enforcement of rules here.
Not sure on history of service. Got car second hand.
With 50.300 PSI and then 35 250 PSI after releasing.gas car behaving the same.
Are you suggesting amount of gas needs to be closer to ideal conditions. Can you give more detail on why you think regassing from scratch would fix the problem.


(This post was edited by stud858 on Mar 20, 2018, 8:20 AM)


stud858
Novice

Mar 20, 2018, 8:14 AM

Post #5 of 14 (765 views)
Re: AC cutting out at speed. Sign In

What about serpentine or clutch causing a problem and switching compressor off until it is reset.
These would be related to speed of car, right. I'm thinking gas has nothing to do with the speef related problem since the two sets of PSI rreadings tried end up with same problem.


(This post was edited by stud858 on Mar 20, 2018, 8:16 AM)


Tom Greenleaf
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Mar 20, 2018, 8:34 AM

Post #6 of 14 (754 views)
Re: AC cutting out at speed. Sign In

You've been advised already of the 1st step to diagnose this if doing this alone doesn't work or change this. System is VERY sensitive to the exact charge you can only know that by vacuuming out the total charge and putting back in the known listed charge amount. Capacities are much lower than much older vehicles and very fussy about it.
The gauge readings are not going to help much until known charge is done.
This exact model not sold to the US so no specs for you for charge amount which is listed under the hood.
What's missing now is what conditions were pressures taken? What RPM and what temperatures? Was fan running and pulling air the correct direction?
A bad/dirty condenser is still a maybe by looks might hide debris between in and radiator?


A/C is not a put some refrigerant in and take some out and see what you get you'd have to be seriously lucky to stumble on close enough. These are charging procedures for a system when it's known ready for a charge at all which it does or you'll never find the reason for it not working normally up to harm it badly.


If your shop or mechanic can't do this you need another place for help not just gauges and wild guessing.


Follow this.......
> http://autoforums.carjunky.com/..._A/C_SYSTEMS_P45460/ <


That's it now you have no clue how much is in the system,


T



Hammer Time
Ultimate Carjunky / Moderator
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Mar 20, 2018, 9:21 AM

Post #7 of 14 (749 views)
Re: AC cutting out at speed. Sign In

Pressures mean absolutely nothing until you have confirmed the exact amount of charge by weight so you have to completely evacuate and recharge and only then can it be diagnosed.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



stud858
Novice

Mar 21, 2018, 12:38 AM

Post #8 of 14 (598 views)
Re: AC cutting out at speed. Sign In

Thanks. I understand what you mean. Bit I fear I have little hope in gassing by weight. All the shops use a simple gas bottle and pressure gauges. Even if i take it to toyota here in Thailand without seeing with my own eyes them doing it Ill ussume they do as all places here in Thailand do, the butcher quick way. I will visit them but unless they let me see them do it the weight way I wont bother because I won't know for sure if I'll be in the same situation. While hunting down weight gassing Ill try and notice other symptoms to guide me.


stud858
Novice

Mar 21, 2018, 12:48 AM

Post #9 of 14 (596 views)
Re: AC cutting out at speed. Sign In

As I cannot easily regass by weight. If we assume my gas is good, are there any other checks i can make.
I agree not normally good to jump over checks but in my case I would like to eliminate other things nefore chasing around for a shop that regasses by weight.
I may never find one here in Thailand that does that.
Going back to clutch or serpentine. Ate they possible problem areas for my described symptom or not related?
Any other switches related to speed of engine involved?
Again, i agree with your points guys but regassing from weight may be out of my control


stud858
Novice

Mar 21, 2018, 12:58 AM

Post #10 of 14 (594 views)
Re: AC cutting out at speed. Sign In

I feel accepting that the original amount of gas in the car as accurate and giving 50 300 PSI rreadings are reliable to help with fault finding. Im suspicious as to why the shop released gas.
So 50 300 would suggest high side too high and suggest a blockage on high side, right. But the fascinating thing, blockage only at high speed driving. At idle system works.


Tom Greenleaf
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Mar 21, 2018, 3:24 AM

Post #11 of 14 (580 views)
Re: AC cutting out at speed. Sign In

Clearly you lack the right help equipped to do this in your area. Nice to use pressures do help with diagnostics even better when you know it's the correct amount of PURE product not all messed up with air or worse, wrong products, sealers or tricks attempted before probably just by age.


What you don't see is the pressure when driving it which you can if you have gauges with longer hoses watch what goes wrong they aren't doing that. System is supposed to shut down when out of spec in real driving situations not just at idle. That's why we beat on that you must know charge be known AND must only be put into a well held vacuum. If your shops and area don't want to invest to do that all A/C will fail in the last couple decades and more of vehicles with A/C.
*****************************
This is what might be found and known best if you (the shops) followed what we are saying. If known charge did the same things then it could be icing up the evaporator in dashboard, pressures may spike too high just working too hard with other failing parts.


You are screwed if you don't even have well equipped shops or help with the equipment for this sure seems by your description it's just pot luck each time can work but not for that long before it's no longer worth fussing with system would be destroyed,


Tom



stud858
Novice

Mar 21, 2018, 5:04 AM

Post #12 of 14 (548 views)
Re: AC cutting out at speed. Sign In

Sounds good. I will endeavour to regass correctly and then find someone who can test pressures while driving.
One last thing I want to understand is how speed of engine relates to compressor. Higher speed means compressor is working harder, compressing more, causing colder more flow of gas. Anything else to note about speed of compressor and system cutting out at higher speeds. I'll have to visit toyota and ill get back to guys. Let you know outcome.Cheers.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 21, 2018, 5:49 AM

Post #13 of 14 (543 views)
Re: AC cutting out at speed. Sign In

OK - You may not have to check while driving if you can get the "known" correct charge in it. You know it works at all so that's a good sign so far for you.
RPM on compressor questions: It's really a brainless pump the faster it spins the more it could pump. Most achieve what a vehicle will use and be stable at about 1,500 RPMs and should be checked there. If idle is say 600 RPM it would be lower pressures and vehicle deals with it. At higher pumping power could be exceeding what the system can handle and shuts down and should. That or too low and shut down and should.
It's a different game to make compressing a gas to a liquid and evaporate it at the right times and places. Home A/C stays the same speed is doing the same idea just always dealing with the same speed or pumping power. Makes it all different for a vehicle including air speed thru the grille moving vs sitting still many have enough air speed to not need the fan(s) so shut them off all controlled by sensing pressures constantly (the vehicle) making those decisions for itself for the request you've made inside. Defaults will shut the system down is the point.
Unlike some "home" A/C when too high or too low if it kept running out of spec you risk freezing where it shouldn't, lack of oil to compressor if not correct or up to choking it with returning liquid gas compressed already but not "evaporated" completely for return to do it all over again.


A few ounces can throw the whole works off. Air if introduced doesn't compress to a liquid and raises all hell.
A/C is it's own specialty for vehicles if a compressor runs off an engine that doesn't hold the same speed no matter how an engine is powered.
Your shops and help seem to be 40 years out of date - nothing personal about that just the amount of gas is now measured by weight once (ages ago now) you just watched a sight glass told you it was correct almost never in use anymore for ages plus not perfect then and wouldn't be now.
A dealer is a good choice of course likely cost you more. They would have to fix a new vehicle if perhaps it wasn't working or right before even selling it so if they can't handle it I don't know how they could be a dealer of new cars?
Good luck. Problem is you need competent help it may only be improper charge?


Tom



Hammer Time
Ultimate Carjunky / Moderator
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Mar 21, 2018, 6:45 AM

Post #14 of 14 (533 views)
Re: AC cutting out at speed. Sign In

Even using just gauges all you need to get an accurate charge is a vacuum pump and an scale accurate to 1/10th of an ounce. They are readily available from tool distributors. I do not believe any dealer in the world will recharge a system without at minimum, an accurate scale.

You CANNOT get an accurate diagnosis without applying a vacuum to the system and getting a weighed charge.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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