I've got a 2002 Sequoia with the dual A/C. The A/C has never cooled all that well since I bought it (back in 2005), but since it was my first R134a A/C, I figured it was just the refrigerant. I did a bit of adjustment on the water control value based on some TSB for that model, but it didn't seem to make any difference. I also checked to see if the TSB for the compressor had been applied, and it looks like it had. However, while fixing the A/C in my wife's 1995 Camry (which I thought was R12, but turned out to be R134a when I checked the specs), I realized that it's possible for an R134a system to be colder than a witche's t*t when adjusted correctly.
So, I'm now trying to troubleshoot my rig. Symptoms are: somewhat cold air when it's not too hot out, colder at highway speeds. Occasionally gives up the ghost entirely and just blows hot air (usually on the days I need it the most).
I've checked the auxillary pusher fan in front of the condenser, and it seems to be working OK. The condenser itself seems clean. When the system is running, the sight glass is milky white (not just bubbly), but is clear when the system isn't running. Operational low side pressure is 53psi, operational high side pressure is 245psi. Ambient around 85-90F. According to the FSM, specs for the dual A/C are 36-51 psi low, 275-305 psi high, so my high side pressure is pretty low, and the low side pressure is pretty high.
To me, the pressure readings sorta-kinda indicate a duff compressor, but I don't understand why the sight glass is milky white. Any suggestions?
not an expert here, but I have fixed a dozen or so A/C and have replaced most individual parts.
Anyway, my 0.02. You sight glass should bubble or foam for a couple of seconds when the compressor kicks on, then it should run clear. Clear when off is normal and not indicative of anything other than there is some freon.
It sounds like a simple undercharge. Your high side is pretty high. I would watch that and charge a little with 134a until you get a clear sight glass, then evaluate the system and pressures, etc. If the bubbles don't get better with 1/2 to 1 can STOP don't add any more.
You may need to evacuate it, leak check it and recharge it. You must use a recovery compressor for this or maybe you have a contact that has one.
Good Luck.
PS - Normal waivers apply. The pressures are high enough to be deadly from explsion or fire, etc. Attempt any and everything at your own risk.
I'm thinking my A/C is under-achieving also. I haven't done the sight glass test yet; but I did stuff a thermometer into the dash vent. The best I've seen is a 20F drop from ambient.
yes it is under performing. My seq delta from outside temp is about -40 deg F
This will vary. The smallest ambient is idling sitting still with high fan. the best ambient delta will be on the highway with a lower fan. the lower fan allows longer dwell time which gives a lower vent temp.
You have a very high pressure delta from low to high guage pressure. That looks like your compressor is doing a good job.
Remember that the Low side pressure is also an indication of temperature. If if it just warmer because of low freon the pressure will go up.
I still think you are low.
Have you ever added freon? It is a fairly straightforward operation.
also the most common place for a slow leak is the schrader valves in the high and low side ports. With a special tool, these can be changed without losing any freon from the system. The tool is a JRA valve core remover/installer. You can get one for under $30 or a kits with 6 different sizes for $125.
not an expert here, but I have fixed a dozen or so A/C and have replaced most individual parts.
Anyway, my 0.02. You sight glass should bubble or foam for a couple of seconds when the compressor kicks on, then it should run clear. Clear when off is normal and not indicative of anything other than there is some freon.
It sounds like a simple undercharge. Your high side is pretty high. I would watch that and charge a little with 134a until you get a clear sight glass, then evaluate the system and pressures, etc. If the bubbles don't get better with 1/2 to 1 can STOP don't add any more.
You may need to evacuate it, leak check it and recharge it. You must use a recovery compressor for this or maybe you have a contact that has one.
Good Luck.
PS - Normal waivers apply. The pressures are high enough to be deadly from explsion or fire, etc. Attempt any and everything at your own risk.
Yeah, the milky-white look of the sight glass would normally make me think the system is undercharged (or the refrigerant is contaminated, but I'd think it'd stay white with the system off in that case). The low-side pressure just seems awful high for an undercharged system, 'tho. The high-side pressure seems high for a "normal" system, but the specs given in the FSM are quite a bit higher for the dual-evaporator A/C system (which I have) than for the single-evaporator system. I hate to guess and hope, but I suppose tossing a half can of refrigerant into the system couldn't hurt things too badly.
I think you may need to do a better search on here. This is a common problem for the Sequoia. Mine does it but only on the hottest days and after sitting idle for a very long time.
Some say on here say you need to insulate your piping under the hood better. I’ve bought the insulation but never done this mod out of laziness.
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Toyota spent extra bucks providing the sight glass (American car makers often don't) and the factory manual explains how to interpret the sight glass. Milky white sight glass when the compressor is running = foam = undercharged condition = marginal cooling.
The likely reason your compressor sometimes won't run is because undercharged condition = low system pressure = pressure sensing switch prevents the compressor from running.
The compressor oil circulates through the system with the refrigerant so undercharged condition = poor oil circulation = compromised compressor lubrication. The pressure sensing switch stops the compressor from running to protect it against the damaging effects of poor lubrication.
Normal center dash vent temperatures should be in the 38-44 degree range when the controls are set for maximum cooling regardless of outside temperatures. Temperatures from the side vents should be a few degrees warmer.
Ended up having to add most of a 12oz can of refrigerant before the sight glass went clear. Pretty weird, too -- there was basically no "big bubbles" stage in the sight glass like I've seen in other systems -- it went straight from "foamy white" to "clear". Low side pressure never budged off of ~55psi (at 85 degrees ambient). That low side pressure still seems high, but it's hard to argue with the sight glass.
I'll put the system through it's paces to see if the problems are completely fixed by such a simple tweek, or if this is just the first layer of the onion...
Glad to hear you had time to work on it. The vent temps and performance will be very informative.
Also remember that the pressure of the hi and lo side are not an indication of a full or low charge. the pressure of the 134a gas will be the same based on it temperature not on the volume in the system. That is why you can judge whether a container is full just by the pressure. You have to take into account its weight, pressure and temperature. Let us know how it come out.
After letting the parts age on the garage shelf for a year, we suddenly went from highs in the low 80's to triple digits, so I quickly became motivated enough to work on the rig.
Evac'd the system, and changed out the expansion valve on the rear A/C unit. The instructions in the FM were full of hooey -- once the trim was off, I was able to change out the expansion valve without having to pull the entire unit (a bit cramped, given I've got sausages in place of real fingers, but do-able). Also changed out the receiver / drier, given I had no idea when, if ever, it had been changed out. Refilled the system until the sight glass ran clear (a bit over 3 12-oz cans).
While I haven't yet given it the ultimate test (sit in sun all day in triple-digit temps, then let it try to cool), all other tests have it cooling down as well as our Camrys -- pretty impressive given there's way more volume to cool in the Sequoia.
Also ran into a slow leak on the suction (low) side schader valve...guess I need to get the parts on order for that fix. At least that's a simple one.
I have read most of the information about the problems everyone has been experiencing with their a/c's and never saw a question about how long a system should take to equalize once it is turned off. Years ago, if this took longer than a couple minutes you had a restiction(probably the expansion valve). My '04 Sequoia takes over 15 minutes to fully equalize. It doesn't cool up to my standards and I was wondering if maybe this was a problem, or is their just some check valves holding it back?
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Help diag A/C problem
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