ejamsrhere

Ok... I had my engine rebuilt by a friend about six months back... Everything came back great, but the AC wasn't working when I got it back. It was blowing cold previous to having the work done. I'm wondering if it isn't as simple as a wire being unplugged or something. When I turn on the AC at idle, the RPM's don't change. It makes me wonder if it is even getting turned on... Anyone have any bright ideas?

PirateFins

Well the only thing I could think of might be if during the rebuild he removed the AC refrigerent lines letting all of the R-12 escape. Now your system would be bone dry and will not kick on. I think there is a pressure sensor that keeps you from burning up the ac system.

ejamsrhere

That may be possible. I think there is some R-12 in the system though. Perhaps it got too low. Is R-12 legal to buy in california?

Flamedx4

First, lets assume they didn't crack the lines and let out the refrigerant... Under the hood, locate the a/c compressor. With the engine running and the a/c off, you will notice the mechanism on end of the pulley doesn't rotate, the pulley just free-wheels. Turn on the a/c and the magnetic coil should engage the pulley and now the end of the pulley should rotate. So, my guess is it won't rotate. Turn off the engine and find the wire coming off the compressor and see it it's been left unplugged. That would be my first guess. Does your voltmeter read normal? If that also seems a bit off, they may have left the ground strap from the block to the frame disconnected. Aside from that, did you check the fuses? The compressor may have its own fuse. (Guessing on that one.) Also, near the condenser you should find a small cannister in the a/c lines that has a sight glass on top of it. Very close to that is a fitting installed in the lines where there should be a pressure switch. Again, I'm not familiar with your particular model, but this switch will have 2 to 4 wires on it. Make sure that is plugged in to the harness.

There could be more to check but without knowing precisely where the parts are in your rig it wouldn't help much for me to describe them. One, for instance, is the resistors that should be on the firewall side of the a/c/heater core box. They could be unplugged too, but I coudn't tell you where to look....

Maybe these tips will help though.
Good luck!

ejamsrhere

Excellent. Thanks!!! I'll take a look at that tonight

Flamedx4

If on the other hand the pulley does rotate, look in that sight glass you found. Within a few seconds of turning on the a/c you should see some bubbles go by. The number of bubbles should drastically reduce to near none in a minute. Too many bubbles or too few can be the result of too much or too little R12. (Believe it or not, an overcharge will sometimes not blow cool too, because the pressure switch will short cycle the system.) Also, if the clutch does engage, the heater valve may be faulty or if its a cable - misadjusted. (Trying to think of anything you can check easily.) And, you *could* call the guys who did the work and ask them about it.... my experience is most professional mechanics know full well they can make mistakes, and if you ask rather than launch on them they're glad to help.

Cheers!

ejamsrhere

Well... I looked at the compressor. Couldn't believe it. No belt at all... How sweet is that.... when he went to go put the car back together he forgot a belt. I took it to a shop and they checked the R12 and said it was empty. They quoted $180 for belt and R12 with no guarantee because they said they won't know if it's leaking or not. Sweet deal.

My99

I've heard that you can put the R134 in the R12 systems and it works fine. i heard it first-hand from someone who did this. Anyone have any input on this? I also heard that you can buy the switch-over kit yourself at an auto-parts store.

The a/c belt itself is easy to put on. Getting to the point that you can put it on could be a little more hairy though. If my memory serves me right, you'll have to take off the shroud, fan, and alternator belt in order to get it on. I can't recall though for certain. (I sure as hell ought to be able to, I just put on the belts less than a week ago.) I can definitely check it out when I get home tonight and let you know if you need. If you have patience and wrenches though, you can do it. I'm in the same boat you are. I didn't unhook my a/c condenser when I did the motor swap on my 90 for fear of losing coolant. However, it's not kicking on the compressor, so I'm assuming that it's low on refrigerant from the PO. I may check the pressure and see if it's low or what. For 120 dollars, I'd say do it yourself.

apc

I've done the R134a conversion using the kit from Wally World with no problems. That was 3 years ago.

Flamedx4

I'm always amazed Toyota systems have held their charges for so many years. Good quality fittings etc. Anyway, yes, a changeover is easily within the realm of most do-it-yourselfers. But a kit, you can't just put R134a in without a couple changes first. Basically you dump the system, replace the schrader valves with the other type, or put piggy back adapters on them, replace the dryer and expansion valve. Remove the compressor and dump the oil out of it. Replace it with the new type of oil (included with the kit.) Then evacuate and recharge the system. The system does not have to be flushed out with cleaner, the residual old oil doesn't cause any problems with the new oil. The R134a will not stay in the old hoses as long as the R12 did usually (smaller molecule and more volatile - it can find a way out where the R12 couldn't get through.) R134a systems will need recharging more often, and coverted systems probably more often than that. When you do it yourself you can't evacuate the system and I feel that's critical, so I'd have it charged by a pro.

Mohamed

Dude if you live near Sacramento and talked to me about a month ago, I would have done all you needed to be done on your a/c (granted though you'd paid for any necessary parts). My opinion now though is don't retrofit, R-12 is still cools better than R-134 systems. R-12 is expensive so I'd try to find that leak, a good comptent mechanic should find it either with dye or a halide detector (if large enough). I get R-12 at cost for $3.00 an oz, but shops may charge as much as $15 an oz, which adds up for a 2 lb system (which I believe the 2nd Gen runners are). And yes per the Montreal Protocol, you must be certified to handle CFC refrigerants (or purchase in this case) which are like R-12, or R-22., in any state. Might I suggest http://www.polarbear-air.com/ in Sacramento, nothing but excellent comments heard about them, and prices reasonable.

ejamsrhere

Man Mohamed... that’s really cool of you. Thank You! I've been calling around to get quotes. One place said he'd convert it for $250 Parts/labor... the next place said they'd do it for $120. The funny thing is that the cheaper is the more reputable shop. It seems that changing over to r134a might be the better bet in the long run. What is the difference in cooling capabilities?

Mohamed

The way an a/c works is air passes through an evaporator and the evaporator acts like a heat exchanger. As your cooling system uses coolant to exchange heat, your a/c system uses refrigerant to exchange heat. R-134 is one form of refrigerant that put a bit more pressure on a system, as a result you use less refrigerant vs R-12 (when you do a retrofit you use like 70-80% the amount of R-12 to put in R-134a, generally, and this is why you want to check for leaks as the excess pressure plus the molecule itself leaks out faster than R-12). Sometimes that isn't even enough and barrier hoses are installed to handle the excess pressure. My theory is there isn't enough liquid that passes through an evaporator when you do a retrofit so cooling capacity is reduced (yes actually inside an evaporator your refrigerant enters as a liquid and comes out a vapor as it absorbs heat and changes states). Basically the point in all this, an R-12 can handle a heat load faster and sometimes more so than a R-134a system.

If you do decide to do a retrofit, make sure the shop you consider reputable replaces the high pressure blow off valve with a switch, if they don't know what you are talking about, find another shop. In case you don't trust your shop and are looking for a reputable shop (besides the dealer) try the MACSW website for certified shops.

jns

APC,
I have a 91 4Runner,too and am looking to convert it to R134a.Did you flush your system out with some chemicals first or change your receiver/dryer?Thanks for any help you can give me.

Jeffires

I know this thread is old, but I've been doing research about the approach I should use to get my AC going for the summer. (I'll move this if it's not acceptable) There are mixed opinions concerning how well 134 works compared to 12, and how much conversion must be done to retrofit.

My system is still R12, and right now the compressor wont even cycle. The relay is good. I can engage the clutch and run the compressor by giving the clutch 12V. This means my system is too low on refrigerant to operate.

I am trying to decide if I should go ahead and switch to 134, so I can work on the system on my own in the future. I'm not concerned about cutting costs, I just want the AC to work as well as it can.

Anyone else getting their system ready for the summer? How is everyone's retrofit to 134 holding up?