A/C Pressure cutoff switch bad?
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A/C Pressure cutoff switch bad?
I am stumped on this one y'all. I have a 98 Expy and recently my wife was complaining that the A/C would blow warm air up front intermittently. However, she told me if she turned the rear air on this symptom would go away and all would blow cool. I added a can of 134 as the pressure was reading low....37low and 150 high. This seemed to improve the condition somewhat with the new readings at about 45 low and 155 high. However we took the annual in law Christmas journey(about 1000 miles) this past week and it seemed to cool fair but only at about 50 degrees. About once in every ten start ups it would blow warm air even after getting on the highway at full speed. However if I turned the A/C off and on again it would sometimes do the trick...............I'm bumfuzzled on this one. As always thanks for your support!
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Joined: Feb 2003
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From: Eastern WA
The fact that the low side reads 45 psi and not 37 after adding freon implies that it's now overcharged. This assumes the conditions were equal when the pressures were taken (ambient temp, engine speed, blower setting, etc). Remember, pressure and temperature are related; higher pressure equates to higher temperature. Also, dumping in an entire can at once on a system that is slightly off on the pressures is condusive to overcharging; for correcting minor undercharged conditions usually adding freon in 4 oz bursts followed by letting the system stabilize then take pressure reading is preferred. These systems use a critical charge and therefore deviate much from that charge. In the old days there was a receiver that stored excess liquid refrigerant.
*When charging, you should have the blower on the highest setting and the engine reved to around 1500 rpm. I like to keep the windows open too. Be aware that the warmer it is outside, the higher the pressure will be on the high side (normal).
*When charging, you should have the blower on the highest setting and the engine reved to around 1500 rpm. I like to keep the windows open too. Be aware that the warmer it is outside, the higher the pressure will be on the high side (normal).
Last edited by CowboyBilly9Mile; Jan 2, 2006 at 10:01 PM.
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thanks for the responses bill and cheez. cheez, i don't think it is the selector because the whole vehicle blows warm now......at certain times and previously the rear air was cold while front was warm. bill, i tend to agree with most everything you said but what would you say the optimal pressure would be on hi and low sides. all readings were in fact taken just as you described and the system was also charged as you described. thanks for the help.
patrick
patrick
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