A/C question...

[DarkDevilMMM]

ok, my new nightmare, my A/C went out, I haven't use it for a long long time, so I really don't know when it went dead. Happens the other day when I try to turn it on, the a/c clutch wasn't moving at all, so I thought maybe my feon is out. Today I went to vacuum out the whole system, install the R134a retrofit kit per instruction and VFAQ. now the a/c clutch turns on, but still no a/c, I am stumped, what else can I check? I search on this site and I read this I checked the plug on the thermostat, working ok I think. I switched out the a/c relays, I checked all the fuse, all intact and ok. so I really don't know what's going on, maybe my compressor is dead? oh one more thing is, the a/c lines are hot to touch, maybe because my engine was running a long time, I don't know if that's normal or not, anyways, any suggestions?

to recap, A/C clutch DOES TURN ON, but no A/C blowing, please help, thanks.

 

[atc250r]

If the clutch is going on but the air coming out of the vents is still warm then it could be a clogged or bad expansion valve. You really need to get some gauges on it to figure out what is causing the problem.

John

 

[DarkDevilMMM]

what gauge and where to measure? I have a gauge from the retrofit kit and measure good on the low pressure port.

expansion valve seems fun to get to, and is there a way for me to confirm that it's that valve that's causing the trouble before I tearing everything apart? thanks

 

[atc250r]

I'm terrible with A/C stuff but you really need two gauges so you can see the high and low pressures on the system. I believe if the pressure difference between the two isn't enough then it is the expansion valve.

John

 

If you have a logger, you can see 2 things:
1) you can see if the A/C switch is turned on
2) you can see whether or not the ECU is activating the A/C clutch.
You need to see first whether the ECU is ever seeing the A/C switch being turned on. If not, the +12 volts from the switch has to go through that temperature switch on top of the thermostat housing, and then through a low pressure cutoff switch next to the dryer/accumulator thingy. Either one of them being open will cause you not to see a valid "A/C switch ON" with the logger, but it is almost always an issue with the temp switch on the thermostat housing. The wiring gets brittle and rusty. I got tired of fighting with it and just cut the wires off and twisted them together. /ubbthreads/images/graemlins/uhh.gif

 

[atc250r]

Quote:
now the a/c clutch turns on, but still no a/c



/ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/grin.gif

John

 

[s_firestone]

Ok, two things you really need to do. Replace your Drier(front drivers side engine bay) and expansion valve(bolted to the evaporator). If you are retrofitting to 134a you really need to replace the O-rings. The expansion valve is a bugger because you have to pull the evaporator.

How much R134a did you use? It usually requires no less than 2 cans (sometimes 3 or 4). Vacuuming the system out you are ahead of the game already.

There is also a pressure switch which will not allow the AC to come on if the pressure is below 30psi.

If the compressor is coming on, your gauges should read up to about 30PSI on the low side (indicating that the compressor is pulling) and up to 250~350 PSI on the high side. Remember all this depends on the temperature. R134 will always show different head pressures than R12.

If your A/C clutch is working feel the lines going into the passenger side firewall right above the fuel filter. One should be hot, the other cold. If they are not, refrigerant is not flowing. There are several possibilities. Not enough refrigerant, too much refrigerant, too much oil, a restriction (in a line, the drier, or expansion valve), or a bad compressor.

Whenever switching I recommend as you replace O-rings, blow each section out one at a time with brake parts cleaner(not carburetor cleaner) and an air compressor to remove the old incompatible mineral oil. Use either PAG(Poly Alkyl Glycol) oil or preferably POE (Poly Ester Oil). The brake parts cleaner evaporates leaving zero residue.

If you suspect a compressor buy known-working replacement from someone. It should cost between $50 to $100. Compressors are normally filled with the full capacity of oil at the factory(and when repacked for sale). You want to open the caps and turn the compressor on end and measure the amount of oil removed into a cup. This takes about 20 minutes of turning, holding, dripping. You will then replace the same amount of R134a compatible oil.

The compressor only takes about 30 minutes to replace from start to finish(expect about 2 hours 1st time). I'm working on a VFAQ for the A/C system and I'm collecting pictures. I'll post a couple pictures of bolt locations later this evening.

But if you have any questions at this point, feel free to ask.

BTW what kind of vaccum pump are you using? If you are using a venturi pump that piggybacks onto a compressor, it will be insufficient to pull a vacuum high enough to boil water out of the system.



I have a question, did you add oil to the system?

 

[DarkDevilMMM]

^^ thanks

I add 2 small can of oil, one PAG and one Ester, 1 large can of R134a and the gauge said I am full already, so I think there's a blockage or some valve isn't turn on, either mechanically or electrically. since the clutch is turned on, so I assume all the sensors are ok, now is the question of where it is blocked.

vacuuming is done at an A/C shop, they use some type of vacuumming pump and hook it up directly to the port, I don't think it's a piggyback to a compressor, I could be wrong tho.

replacing the compressor or dryer is not a problem at all, but I just don't want to open up the system, replace a part, all the necessary she bang like vacuuming and filling, and find out that it's still not working. hey this situation have been happenning to me a LOT lately, I end up paying or doing more work then the problem itself.

but again, if all fails, I can always tear the whole A/C out, 30+lb less, and I can use thicker IC/radiator, also can relocate the alternator, so I can use bigger turbo+wastegate /ubbthreads/images/graemlins/grin.gif thanks for the reply

 

[s_firestone]

I understand your pain. The drier and expansion valve(thermally actuated orfice similar in design to an oven thermostat) are both recommended for replacement. The failure modes of a compressor(not the clutch) will usually show as inadequate differential pressure, or the bearing will fail(noise or seizure). I'll post the service limit differential when I get home.

You might look at the sightglass on the drier(under the radiator coolant bottle) to see if your seeing bubbles, that will at least tell you if coolant is flowing on the high side(liquid line). Do you have the service manual or would you like me to post the compressor diagnosis page?

The drier costs about $40, the expansion valve about $45, and a used compressor about $50 up. It is noteworthy to mention that a compressor failure can leave debris downline that can come back and kill a replacement compressor or cause a restriction.

Don't think I didn't consider ripping my AC out, mounting a 2nd alternator and setting up an array of Peltier thermo-electric cooling modules. But I calculated to cool 1KW I would need 70 to 90 Amps at full load. Of course I could cool the car to 70 degrees below ambient temperature in 10 minutes. I may still try it.

 

screw it, take it out

NO A/C = MOORE BOOST

 

[s_firestone]

KEYDIVER CHIP = KEEP A/C PLUS MORE BOOST

Have your cake and eat it too.

 

Quote:
Quote:
now the a/c clutch turns on, but still no a/c



/ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/grin.gif

John



Yeah, but who has time to read the whole post? /ubbthreads/images/graemlins/tongue.gif