Air Conditioner Not Working 1991 Ls400

[sisterpete]

Hi All,

Hope this is not answered somewhere else on here.... I couldn't find it. I tried to search, but it will not allow ANY word less tehn 4 characters.... oh brother.... ac, air, the word not.... all are under the limit, so i couldn't look for "ac not working", air conditioner not working", not ever simply "air conditioner".....

anyway, the ac in my 1991 ls400 is not working... stopped putting out cold air, compressor still running, so i checked and it seemed to need some 134a... it has been changed... charged it, but still nothing... here's some info

high side is running about 230lbs, low side pulls a vacuum when turned on, comp is running, but not very hot, tubes gonig to the comp are really hot, nothing on the low side is cold at all...

any thought would be nice... thinking maybe the dryer is plugged???? cant seem to find where it is though

thanks for your input, you guys have been a great resource to me since i purchased this

[wwest]

Hi All,

Hope this is not answered somewhere else on here.... I couldn't find it. I tried to search, but it will not allow ANY word less tehn 4 characters.... oh brother.... ac, air, the word not.... all are under the limit, so i couldn't look for "ac not working", air conditioner not working", not ever simply "air conditioner".....

anyway, the ac in my 1991 ls400 is not working... stopped putting out cold air, compressor still running, so i checked and it seemed to need some 134a... it has been changed... charged it, but still nothing... here's some info

high side is running about 230lbs, low side pulls a vacuum when turned on, comp is running, but not very hot, tubes gonig to the comp are really hot, nothing on the low side is cold at all...

any thought would be nice... thinking maybe the dryer is plugged???? cant seem to find where it is though

thanks for your input, you guys have been a great resource to me since i purchased this

Sounds as if the reheat/remix vane/door is stuck in the full heat position. Luckily on the 91 you can check for that pretty easily. The same servomotor that drives the reheat/remix vane/door has a push/pull cable attached that also drives the HOT coolant flow valve open/shut. Have someone cycle the control from max cool to max heat while you watch the actions on the hot water flow valve in the engine compartment at the top center of the firewall.

The water valve does stick and if so you can make a temperory fix by simply slipping the cable off of the valve and then tying the valve off in the closed position. As "cooling season arrives I always try to remember to tie the valve off into the closed position until cabin heat is more consistently needed in the fall, resulting in a dramatic improvement in A/C cooling efficiency, especially when used along with recirc (NEVER use recirc in heating mode). This procedure will also improve FE somewhat.

[JENunnez]

Sounds to me either expansion valve or the orifice tube is stuck or blocked. Thats the only way to get a vacuum on the low side and the high so, eerrrr, high.

Hope this helps.

[sisterpete]

i'll check these ideas... can you tell me where the orfice tube is? my understanding is the expansion valve is inside by the evaperator.... although i dont' really know where that is. any tutorials on checking and or changing these two pieces would be helpful also.

thanks for the help guys

[TA in KC]

i'll check these ideas... can you tell me where the orfice tube is? my understanding is the expansion valve is inside by the evaperator.... although i dont' really know where that is. any tutorials on checking and or changing these two pieces would be helpful also.

thanks for the help guys

You either have an expansion valve or an orifice tube, not both. If I recall correctly, Lexus LS cars have an expansion valve.

What part of Kansas are you in? I have the name of a mechanic that does A/C service for very reasonable prices, if you decide you just want to pay someone else to fix it.

[sisterpete]

i'll check these ideas... can you tell me where the orfice tube is? my understanding is the expansion valve is inside by the evaperator.... although i dont' really know where that is. any tutorials on checking and or changing these two pieces would be helpful also.

thanks for the help guys

You either have an expansion valve or an orifice tube, not both. If I recall correctly, Lexus LS cars have an expansion valve.

What part of Kansas are you in? I have the name of a mechanic that does A/C service for very reasonable prices, if you decide you just want to pay someone else to fix it.

i'm in wichita

[JENunnez]

I'd leave it to someone that knows about A/C and has all the speacial tools. It's not that easy.

Plus it could be dangerous, the refridgerant under preasure can burn or cause eye damage.

[TA in KC]

Have you looked at your car's service manual?

techinfo.toyota.com

[wwest]

Sorry, I assumed "vacuum" meant in comparison to the high side pressure. not an actual vacuum. The low side should never be lower that about 40PSI of positive pressure. A vacuum would indicate a blocked EPR or expansion valve. The early LSes used an EPR, Evaporator Pressure Regulator, to quiet the "hiss" and other noises made as the refrigerant expands into the evaporator volume, or so they told me.

The EPR is mounted right at, next to, the firewall in the low pressure line leading to the compressor intake.

I have had at least two instances over the years that resulted in the A/C not working. The first of these while traveling over the continental divide outside of Helena MT and the second in the Mountainous are of northern CA near the OR border. Both, seemingly, have to do with high altitude operation. I recovered, in both instances, but turning the system off for a brief period, long enough, one would expect, for the evaporator to thaw out were that the problem. But since I always had good system air outflow I'm pretty sure the evaporator wasn't frozen.

I suspect the EPR was. I have often seen, observed, many times over the years, the compressor intake line that crosses under the front of the condensor covered with 1/4" or more of ice/frost. The only way that can/should happen is that some of the refrigerant cooling capability is reaching this area. IMMHO the only thing responsible for that would be the EPR and given that conclusion the brief inoperative periods I experienced was most liekly due to a frozen, LOCKED, EPR valve.

EPR valves are more typically used on systems with multiple evaporators, say minivans with front and rear A/C, to prevent one evaporator from "stealing" all of the cooling capability.

[sisterpete]

I'll have to see if this has an EPR or not. Yes, it's actually puuling a vacuum on the low side.

also, i'll check out the toyota link