zz_denis

Hi guys,

Im in the process of installing A/C system on my 1998 4runner (3RZ). The truck didn't come with A/C from the factory, so Im swapping the whole system in. I bought brand new OEM evaporator, condenser, drier, compressor (rebuilt). Hoses/hardware/brackets and random bits and pieces came from a donor truck.

For those wondering, the truck is pre-wired for A/C from the factory and all the connectors/holes/etc are already there, its just a matter of bolting the parts in and charging the system.

So here are my questions. I've been searching for hours (literally), and cant find the info.

1) How much PAG oil does the complete, DRY system take? I cant even find the answer in original A/C service manual. All I can find is some suggestions on the forums how much oil to add if you replace a certain A/C component, but not the spec for the full system.

2) I got a rebuild compressor from a 98 V6 4runner. Didn't know V6 and 4cyl compressors were different... The V6 compressor fits just fine, but it has a larger pulley than the 4cyl compressor. From what I can tell, this is the only difference. Can somebody tell me why the V6 compressor has a larger pulley? I would think that it would be the less powerful 3RZ that would need the larger pulley to spin it with less effort..
I have a working 3RZ compressor out of my parts truck, but its very old, and I would rather use the freshly rebuilt one (the V6 one that is). If its not recommended to use the V6 compressor, can I just swap the pulleys, or are there other internal differences?

Sorry for a long post, thanks in advance!

Buckaroo5

Not an A/C expert but can offer the following...

For a '98 T4R- all engine sizes, my reference says system capacity 7 oz (actually fl oz, I think) PAG-46, 23 oz R-134a.

Larger diameter pulley on compressor will spin it at slower RPM. I would not install the compressor with larger diameter V6 pulley on the 4 cylinder. Diameter of crank shaft pulley could be different on the two engines - ratio of diameter of crank shaft pulley to compressor pulley determines rpm of compressor at a given engine rpm.

Good luck,

Buckaroo

zz_denis

Thanks Buckaroo,

I put 7oz of PAG-46 into the system and charged it with 1.4LBS of R134A.
I swapped the pulleys on the compressors, so I now have the proper sized pulley installed.

It was way too cold here the last few days to test the A/C system.

Tried it today, and here's the problem im having:

With RECURC OFF, the system seems to be working fine. Low side pressure pretty stable at 25-28psi, high side - 200-210psi. (Toyota repair manual says 22-36psi low and 199-228psi high is the spec)

However, as soon as I recirculate the air, both low and high sides start dropping, until low drops to 20psi (usually takes about 10 sec or so), and the pressure switch kills the compressor. As soon as that happens, low side quickly climbs back to 35-40psi and compressor kicks back on. It repeats this cycle indefinitely...

Sight glass is milky, but im fairly confident in the accuracy of the scale that I used to put gas in. I put the exact amount that the manual calls for (1.4lbs) I've read that bubbly sight glass might be normal in if cooling performance is OK. Low and high side pressures are on the lower end of the "normal" spectrum though.

What could be causing this issue?

Any advice greatly appreciated!

Buckaroo5

So - I am assuming you have it on Max AC with windows closed. Is the engine at normal rpm? - normally when you test the AC, you take it up to 1500 - 2000 rpm. You should have a temp drop of 20-30F from ambient at the center dash vent. You should have a relatively steady temp after the system stablizes and you shouldn't have much different as you move the thermometer from the center panel vent to the side vent.

It sounds like it's working properly - the system is designed to cycle off to keep the evaporator from icing up. The evap temp drops, low pressure side drops and the system cuts out, then the evap temp and low side pressure rises and it cuts back in again. When you have the recirc on, you have reduced the cooling demand on the system so it doesn't have to run all the time. As your ambient temp increases, the cycle off time will go down on recirc. At 100F ambient, you might have little if any cycling.

Also - would agree that the milky sight glass is normal for R134a. Sight glass not a good indicator for charge level on R134a. It was a very good indicator for R-12.

Buckaroo

zz_denis

Thanks again for a quick reply!

Yes, test conditions are exactly what repair manual specifies -
max fan speed, 1500rpm, windows closed.

Ambient air right now is about 88F.

I know what you are describing is correct (system cutting out when the evap gets too cold), however, it feels like its doing that way too early...

I don't have a thermometer to test it with right now, but:
- With recirc OFF, the compressor runs continuously and the inside of the truck never gets cold (I ran it for half hour). Air blowing from the vents is "cool" at best. I'd guess 65F.
- As soon as Recirculation is turned on, the air temperature from the vents gets significantly colder, but the compressor cuts out seconds later, and the inside air temperature of the truck doesn't get any colder than running with recirc off.

Is it possible that the thermistor on the evap core is malfunctioning?
Also, is it normal for low side pressure to drop to the point where the pressure switch kills the compressor?

Buckaroo5

So I agree, your description of being unable to cool the truck doesn't sound right but you should check the vent discharge temp with a thermometer - if you are getting 63F air on an 88F day, that's a 25F drop which isn't bad. The FSM says you should expect 20F below the temp inside the truck but it also say that it should eventually get down to 35-55F. I know mine is nice and cold.

Yes, the thermistor could be bad but your compressor is running 100% of the time with outside air (not recirc) and the car isn't getting cold. Replacing the thermister is not going to change that....the compressor will still run 100%. To do a quick test on the thermister, you can access it behind the glove box, unplug it and test resistance (you don't have to pull the evaporator). It should be ~2500 ohms at 77F. The FSM has a chart with specified resistance over a wider of temps.

Some questions -Buckaroo

zz_denis

I'll get my hands on an accurate thermometer to test the vent temperature, but I really feel something is wrong with the system. The 3 major components (evap, condenser and compressor) are brand new (as well as receiver), and all other parts came off a parts truck with a perfectly working A/C. So there is no reason for the system to perform poorly...
It takes a while for the air out of the vents to become cold (significantly longer than most other cars I've been in), and like I said earlier - the inside of the truck never gets comfortably cold at 1500rpm idle (again, all other cars I've been in can get cold even at 700rpm idle).

I just tested it on a highway, and the inside of the truck did get pretty cold with recirc on though.

Here are the answers to your questions:
1) Yes, all components were installed (drier being last), oil put in, deep vacuumed right away for 2-3 hours. I have a professional grade A/C machine in my possession with a built in vacuum pump, heated scale, etc.
2) I know that the pressure switch is killing the compressor because it kills it when the low side pressure is getting to 20 psi (as per gauges on my machine). I tested the sensor output (continuity) with system running (senor wires jumped) to verify that this is indeed happening.
3) Im pretty sure that everything is set up correctly. It was an install, but a surprisingly straight forward one. There is really nothing to mess up as far as doors/controls/pipes go. The evap box swaps right in, in place of the non-ac box. All connectors for the evap box, compressor, pressure switch and a/c button were already there, so it all plugged in. And yes, this is a manual control system.

Ill test the vent temperature and thermistor tomorrow, but Im starting to get a feeling that this is refrigerant related. Its possible that the scale on my $3000 machine is off, and I didn't actually put 1.4lbs of refrigerant inside.

maachine

put more refrigerant inside the system and see what happens.

Buckaroo5

Just a detail really but the FSM says that the charge should be 22.92 oz plus/minus 1.76 oz - and that's pure R134a, no additives. That's plus or minus 7.7%. At 1.4 pounds, you are at 22.4 oz, already low by 2.3% vs the target. It seems like we are splitting hairs but if your scale is a little light and you are starting a little low to begin with, you may be on the edge (but hard to believe it could make a difference). But, your pressure is a little low. You might try to recharge it using 1.6 or just a little under that if you have that kind of resolution on your scale and see what happens. That's slightly high out of spec but it would be interesting to see if system performance changes. You have that fancy machine (I am jealous) so you won't be losing any refrigerant. Do you have one of those ID instruments that can confirm that the R134a you have in that cylinder is pure?

Buckaroo