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I have a 99 tarus SHO with ac issues, I have replaced the compresser, orifice tube and dryer plus cleaned the condenser, the cooling fans are working but still wont cool at highway speeds, works fine around town, the manifold gauges show at idle 42 low and 210 high, when the engine is reved high side goes to high and compresser kicks out, low side drops to abt 30 any advice on a diagnosis
thanks Mike Garman
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Sounds like it may be overcharged. That’s just a guess. Pressure readings don’t mean too much unless you know the temperature and relative humidity readings. Also, it’s important to put the correct amount of refrigerant in when performing AC service. More info on AC problems here.
http://www.ericthecarguy.com/faq/solving-automotive-hvac-problems
Good luck and keep us posted.
thanks the check was done and temp was 90 with abt 60% humidity I ve heard these cars ac systems are real touchy on having an accurate charge Is that true? will take it to a shop for that thanks again!!
Mike GarmanYes, they are. Was a vacuum pulled before charging? A vacuum as close to 30 inches as possible for about an hour needs to be performed prior to charging to remove air and moisture from the system. If there is any air in the system it will affect cooling ability.
the vacume was done for abt 5 min and only pulled down to 20 will definitely be taking it to the shop… thanks guys
re did the vacuum and charg properly got the cooling fans working its a lot better but still kicks out at high rpms and builds up pressure on high side
If the dessicant broke in the receiver/dryer, the orifice tube may be clogged. I know you replaced the orifice tube, but maybe there was still trash in the lines plugging the new one? This condition can cause unusually high high-side pressures. It could also be a faulty high-side cutout switch, or faulty pressure switch. What are the pressures you are getting? What is the pressure reading on the high side when the compressor kicks off? More evidence is needed before you should take the system apart again. A diagnosis is required.
high side pressures go to 350-400 when engine is revved and it kicks out, I installed a new receiver dryer must be high pressure switch?
No, it sounds like the high-side cutout switch and pressure switch is working properly. The system is designed to cut out the system when the high-side pressure falls between 400 and 425 psi to protect the compressor. I would only suspect the cut-out switch if it was kicking out at a much lower pressure. At 90ºF outside ambient air temperature, your pressures should be somewhere around 35 on low, and below 250 on high.
More likely the culprit is the orifice tube. It is either clogged or was the wrong one. Was the new one the same color as the old one?
yes sr it was same color, also when I pulled the old one out it had oily build up on the condenser side, at that time I suspected to much oil in the system could this be possible even after a vacuum and recharge twice with no oil put in?
Really, the only cause for the low side to be ‘normal’ and the high side to be ‘high’ is if there is a restriction in the high side of the system. Sometimes the condenser can be plugged up, especially if the dessicant bag in the old receiver/drier broke open. 99% of the time it is the orifice tube though. If the condenser isn’t getting sufficient air flow it can cause this as well, but I would say the air flow is probably okay now that the fans are fixed, so we’re back to a restriction situation. I’ve heard it told that too much oil can cause this as well, but I haven’t actually seen that for myself (not saying it can’t happen).
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