Air conditioner not working

DALLIESWRENNJR

MEMBER
1997 NISSAN MAXIMA
3.0L
6 CYL
2WD
MANUAL
230,000 MILES

Have a slight vacuum hiss under dash with car idling and heater turned to max cool or to max heat, no difference. Car gives heat only, A/C manifold gauge shows 34 outside hooked to lines, compressor running. My wife's car listed above sx model 3.0 5 sp man. Car only blows warm to hot air, A/C on/off maxes no diff blend control from max cool to max hot, have plenty of hot air. Only cure is to turn unit off from max cool to max hot, only get got air. There is a small whistle from under dash indicating a vacuum leak, could this be the problem and if so where wife is really not happy with me. Help?

Wednesday, August 12th, 2020 AT 12:01 PM

4 Replies

KASEKENNY

MECHANIC
18,907 POSTS

I suspect we have a leak or just low on Freon in the A/C system as long as the compressor is kicking on. If you have 34 PSI on the low side then that is a good sign that the compressor was running but we need the high side as well. Let's start from the beginning. Check and make sure the compressor kicks on. Next hook up the gauge set and turn the engine and A/C system on and tell me what the PSI is for the high and low and what the ambient temperature was when you were testing this.

Here is a guide that will help with this:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Let me know this and we can go from there.

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Wednesday, August 12th, 2020 AT 4:19 PM

DALLIESWRENNJR

MEMBER
3 POSTS

I am a retired ASE master, been retired almost 10 years, worked as an extended auto warranty inspector in 4 different states. Wife's car, compressor cycles as it should does not run full time, holds approximately 39/43 on low side, ambient temperature is pushing 90, humidity is almost 70, with unit on cold, fan on 1, wife can hear a small hiss on pass side listening under dash, I'm almost deaf, don't hear a lot anymore, pulled radio package to check HVAC controller, no vac lines to it just electrical. Out of practice, not sure where to look anymore. Got any good ideas?

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Wednesday, August 12th, 2020 AT 4:46 PM

DALLIESWRENNJR

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3 POSTS

My A/C gauges are only low side unit, do not have a double gauge unit anymore.

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Wednesday, August 12th, 2020 AT 4:47 PM

KASEKENNY

MECHANIC
18,907 POSTS

I am not sure the hiss is related until we can confirm the high side pressure. The reason is, if the high side is in line then you most likely have an issue with the blend door that is routing the air over the heater core. However, if the high side is not in line then we have an issue with the AC system.

As it stands, your low side is slightly low for 90 degree ambient temp and that high humidity. It should be around 50-55 PSI. Seeing what the high side is doing will tell us what direction we need to go. If you don't have a gauge set, you can rent one from a parts store that has a rental program.

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Thursday, August 13th, 2020 AT 6:43 PM