pirrello

So driving down the road today and the A/C stop blowing cold. Popped the hood and found the compressor clutch not engaging. The condenser fan is running and cycles with the a/c switch. Low side 35 psi. Checked ground connection at compressor. Any links or thoughts? PS - new compressor, running great for 2 years now.

mk378

It takes 50 on the high side to close the switch and start the compressor. With the compressor having been off for a while, high side and low side will be the same. In other words, it appears that almost all of the refrigerant has gone.

Double check by unplugging the pressure switch (on the condenser) and check if it is closed circuit. If pressure is suddenly gone there is a big leak and you need to find it. Recharging will just have it leak out again in a day or two.

94eg!

iTrader: (2)

I would definitely follow mk378's advice 1st....

If that switch is closed, then there are only a handful of reasons the fan would run and the compressor wouldn't....
- Bad Compressor relay
- Bad Compressor clutch coil
- Bad Thermal overload protector (mounted on the compressor)
- Bad wiring
- Bad ECU

It will be up to you to troubleshoot everything. If it doesn't turn out to be a leak like mk378 suggested, get the OEM Bishko service manual CD on rockauto ($25 shipped). It has AC diagnosis flow-charts that will help you test each of those items in a pretty efficient manner. It's important to have the right book fhat includes your specific year as subtle wiring changes can alter the course of the testing.

pirrello

You guys are awesome - thank you.

The pressure thing got me to thinking - When in doubt, look for the obvious. mk378 nailed it on with a gas "dump" and the switch checked out fine. It is not a leak (but it is) as much as it is a component failure. The relief valve on the back of the compressor blew. I originally installed UV oil and the uv light lit up the relief valve and blow off areas around it.

This is a 1993 Del Sol s 5m - the a/c has been converted from R12 to 134a. The compressor is 2 years old. The install was 4 oz. of PAG46 (uv) and 20 oz of 134a. I installed the 134a by weight.

? - The original system capacity for R12 required 23 oz and 5 oz of mineral oil? Besides the compressor no other components were changed. Do gas amounts need to be compensated for system capacities to accommodate 134a?
? - Should I install 134a by pressure or by weigh?
? - Is there any way to know how much oil is lost when the pressure relief valve fails? Should I add any as a precaution? If so, how much or should I start over?
? - Has anyone else had problems with these relief valves?

94eg! - Got it ordered. I won't hurt to keep it handy as the car is showing no signs of slowing down!!

pirrello

Also, the Relief Valve is discontinued (PN 38801-PM9A-11). Does anyone know where to find one????????????????????

94eg!

iTrader: (2)

It sounds like you filled it up correctly by using less R134 than R12. Oil capacity should remain the same, so perhaps 5oz of PAG would have been better. Re-check the oil capacity in your OEM shop manual because I've seen false info about capacity for the 94-95 systems floating around.

You cannot charge by pressure. Pressure is a "constant" when compared to refrigerant volume once liquid refrigerant is present inside the system (ie: 10oz in the system is the same pressure as 20oz in the system). Pressure readings on your gauges are indicative of refrigerant temperature at that given point in the system. The only correct way to charge is by weight.

You won't know how much oil was lost. I would definitely start over. The book tells you how much oil "should" remain in the other components. I would drain the compressor and add fresh oil (SuperCool PAG46 or Sanden SP10)....... Full Amount MINUS the amount contained in the other components PLUS the amount needed for a new Drier (since you will have to install a new drier).

I've heard of valves blowing out before on here, but only once or twice. I'm surprised it would happen before the High-pressure-protection switch shut the system off. No idea where to get a new one. Perhaps contact Sanden to see if they have a TRF090 valve.

94eg!

iTrader: (2)

I googled "sanden TRF090 relief valve" and got these hits....https://www.google.com/search?biw=10....0.AVQMiE2hk80

I didn't actually look into the results so do a little research before dropping money one though.

94eg!

iTrader: (2)

According to Sanden's retrofit instructions, use the same amount of oil as the original system required. It's either 4 or 5 oz total (whatever comes inside the new compressor) so conifrm in the book in the section about replacing the compressor.

Here is a link to the PDF: http://www.sanden.com/objects/retro.pdf

pirrello

Thank you - I got the last two relief valves they had (just in case). Thanks for the link and the info.

The rating on them is 500-600 psi - if i am reaching those pressures I must have a problem. The compressor does cycle. If the original R12 pressure switch and system operates at lower pressures - would it be smart to change out the pressure switch? I mean is it possible for the tolerances to change with age? Any links to info regarding operating ranges for these pressure switches or off the top of you head?

I see you recommend changing the drier. Is that necessary if the system never really opened or just good practice?

Lastly, recommended vacuum time?

94eg!

iTrader: (2)

You will have to remove the compressor to do the oil anyways. Driers are relatively cheap.

Vacuum time (from memory) I would say a half hour and then close it and let it hold vacuum for a half hour. The shop manual tells you exactly what they recommend and it's not even that long.

The pressure switch in your AC system is actually a "Dual" pressure switch. It closes at the low-pressure threshold (mk said 50psi) and opens again if it reaches the high-pressure threshold. I don't remember the exact ratings but it will be in your book. If you think it's suspect (and it doesn't cost too much) replace it. OEM is ~$43 online, I'm sure aftermarket would be cheaper.

80440-SM4-003

https://www.oemacuraparts.com/oem-pa...BlZWQtbWFudWFs

pirrello

UPDATE:

Would love your thoughts on this -

Put it all back together and started testing pressures. I put 20 oz after vacuum pull. At idle (650-700 RPM) 52psi Low and 215psi high @ 82 deg F. Ran RPM's up to 3500 and the Low dropped to 30psi and high 350-400psi. I then did a couple of rev tests and notice the compressor was not cycling. Ran the pressure up to 500psi and the compressor did not cut off. The spec on the high cut off is 465psi. Is it safe to say - replace the switch?????

tony_2018

Wow, didn't even pull a vacuum. ***** to the Wall.

94eg!

iTrader: (2)

Those high-side pressures are high. No wonder the safety plug blew. I'm wondering if your expansion valve is stuck closed or something. The book tells you what to look into if one side is high and the other is low etc... I don't know off the top of my head.

mk378

Pressures that high result from too much oil, or situations where the condenser can't work well.

* Fan not working
* Condenser inside passages clogged with debris from an old blown compressor (*)
* Condenser airflow clogged with dirt / bugs / bent fins

(*) Note that the pressure measuring port is BEFORE the condenser, while the pressure switch is AFTER the condenser. If condenser is clogged up, you will see high pressure yet switch doesn't cut out.

94eg!

iTrader: (2)

Well this sounds like a good time for a new condenser. Honda still sells them for about $280 online (includes new pressure switch). Aftermarket is $50-$70 without switch.