a/c goes few degrees lower when car slows down

Hi there,

I just finished the a/c job putting a reman compressor, changed the receiver dryer and retrofitted to R134a on my 86LXi. I changed the seals and pulled a good vacuum. The performance is acceptable. Being able to get down to 45F driving in a Florida summer evening, I have no complaint at all. The day time performance, of course, is just ok. I'm getting about 52F today crusing at 60mph during noon time. But I noticed this strange issue today: when I slowed the car down after highway driving to a red light, the vent temp actually dropped about 5F. My pressure reading (by the time when I charged it) is as follows-

ambient temp = 90F
high side = 210psi
low side = 36psi
engine rpm = 1100

I believe I have about 22 oz of R134a (based on 85% content to R12). I didn't use up two cans of 12 oz R134a.

Also, my driver side vent (the one to the left of the steering wheel) shows about a few degrees lower temp compare to center vent. I expect the other way round. Any clues?

I just saw vinny's post today about the content of refrigent and oil. I believe I didn't put enough ester oil in it (vinny's info shows almost 8 ozs oil). Should I use an "oil charge" to add? or better recover, put more oil and rechange from scratch?

Thanks. - Alex

I think your center vent switch may need to be switched to a different position (you want to see the Blue arrow when using A/C) What may be happening is that at higher speeds hot air from the outside is being forced through the vents (assuming your switch is in the white arrow position) causing the air coming out of the vents to be warmer. When you slow down, less hot air is being forced through so you get cooler air. This is also confirmed by the fact that your driver side (and probably your passenger side) vent is blowing cooler air. So basically I think you have the center vent switched to the wrong setting. Just my $.02

Quote:

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Originally Posted by AC439

Hi there,

I just finished the a/c job putting a reman compressor, changed the receiver dryer and retrofitted to R134a on my 86LXi. I changed the seals and pulled a good vacuum. The performance is acceptable. Being able to get down to 45F driving in a Florida summer evening, I have no complaint at all. The day time performance, of course, is just ok. I'm getting about 52F today crusing at 60mph during noon time. But I noticed this strange issue today: when I slowed the car down after highway driving to a red light, the vent temp actually dropped about 5F. My pressure reading (by the time when I charged it) is as follows-

ambient temp = 90F
high side = 210psi
low side = 36psi
engine rpm = 1100

I believe I have about 22 oz of R134a (based on 85% content to R12). I didn't use up two cans of 12 oz R134a.

Also, my driver side vent (the one to the left of the steering wheel) shows about a few degrees lower temp compare to center vent. I expect the other way round. Any clues?

I just saw vinny's post today about the content of refrigent and oil. I believe I didn't put enough ester oil in it (vinny's info shows almost 8 ozs oil). Should I use an "oil charge" to add? or better recover, put more oil and rechange from scratch?

Thanks. - Alex

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You seem pretty knowlegible about A/C, so I would recommend you ask these questions on the www.ackits.com forum. They have numerous experts that can provide good technical info for you.

Gregg

Quote:

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Originally Posted by '89AccordLX(Rus)

I think your center vent switch may need to be switched to a different position (you want to see the Blue arrow when using A/C) What may be happening is that at higher speeds hot air from the outside is being forced through the vents (assuming your switch is in the white arrow position) causing the air coming out of the vents to be warmer. When you slow down, less hot air is being forced through so you get cooler air. This is also confirmed by the fact that your driver side (and probably your passenger side) vent is blowing cooler air. So basically I think you have the center vent switched to the wrong setting. Just my $.02

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Thanks for the reply. I've always been putting the lever between the two center vents to the blue side. I came across some explanation of the usage of that lever, and if I remember correctly, the blue side is to disallow warm air from blowing from the center vents if we are using the heater. I'll try putting it to the other side and see what happen.

Quote:

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Originally Posted by Gregg86DX

You seem pretty knowlegible about A/C, so I would recommend you ask these questions on the www.ackits.com forum. They have numerous experts that can provide good technical info for you.

Gregg

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Thanks for the suggestions, will give it a try.

Also, are you setting the A/C to Fresh air intake or Recirculation? What may again be happening is that at higher speeds the air is basically pushed into the external vents and the larger quantity of air is not cooled as efficiently as a smaller amount (low speed conditions). Try using the recirculation function and see if the problem disappears. Just my $.02 :D

Quote:

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Originally Posted by '89AccordLX(Rus)

Also, are you setting the A/C to Fresh air intake or Recirculation? What may again be happening is that at higher speeds the air is basically pushed into the external vents and the larger quantity of air is not cooled as efficiently as a smaller amount (low speed conditions). Try using the recirculation function and see if the problem disappears. Just my $.02 :D

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Yep, I thought about this too and I have been using recirulation mode. Thanks.