AC issue, low side pressure bad.

[Blank88]

Hey everyone,

I have a 99 explorer sport and live in pheonix so AC is a must have. It will blow cold for about 3 mins and then what I’ve noticed is the low side pressure goes through the roof and AC doesn’t blow, it’s just hot air.

I tried topping up refrigerant to about 35 psi for ambient temp. Also replaced the AC relay.

When I bring rpm’s up when driving it seems to re engage the compressor or whatever that’s blocking it from working, but if I’m at a stoplight it won’t, only if I’m moving. I’m at a loss of what it could be, have asked some mechanics and they aren’t sure unless they pull the system all apart. Any Input or ideas would be great, thanks.

 

[FordFlintrock]

Hey everyone,

I have a 99 explorer sport and live in pheonix so AC is a must have. It will blow cold for about 3 mins and then what I’ve noticed is the low side pressure goes through the roof and AC doesn’t blow, it’s just hot air.

Need high and low side gauge actual pressures.

I tried topping up refrigerant to about 35 psi for ambient temp. Also replaced the AC relay.

When an A/C system exhibits problems most think it just needs more refrigerant introducing air in the process.

When I bring rpm’s up when driving it seems to re engage the compressor or whatever that’s blocking it from working, but if I’m at a stoplight it won’t, only if I’m moving. I’m at a loss of what it could be, have asked some mechanics and they aren’t sure unless they pull the system all apart. Any Input or ideas would be great, thanks.

Whenever the compressor is engaged it needs air flow through the condenser via the electric fan or fan clutch engaged. Could be system is overcharged, compressor malfunction or a few other things.

 

[Pete Deering]

Hey everyone,

I have a 99 explorer sport and live in pheonix so AC is a must have. It will blow cold for about 3 mins and then what I’ve noticed is the low side pressure goes through the roof and AC doesn’t blow, it’s just hot air.

I tried topping up refrigerant to about 35 psi for ambient temp. Also replaced the AC relay.

When I bring rpm’s up when driving it seems to re engage the compressor or whatever that’s blocking it from working, but if I’m at a stoplight it won’t, only if I’m moving. I’m at a loss of what it could be, have asked some mechanics and they aren’t sure unless they pull the system all apart. Any Input or ideas would be great, thanks.

1. "The system works for 3 mins."
?What is the center vent outlet temperature?
2. "the low side pressure goes the low side pressure goes the roof." The evaporator core temperature is high.
? What is the pressure?
3. "I tried topping up refrigerant to about 35 psi for ambient temp."
? what are you using for reading? A AC can gauge?
4. When I bring rpm’s up when driving it seems to re engage compressor"
This seem that the low pressure switch rises above set point and turns on AC clutch.
5. "but if I’m at a stoplight it won’t, only if I’m moving. I’m at a loss of what it could be, "
There is no air flow across the condenser, when at the stop light. The high side pressure will go up.
There is a loss of cooling( heat extraction), when at a stop.
6. This sound like you are low in freon. I know at high ambient temperature the compressor will run with very little Freon in the system.
7. It also sound like your clutch fan is not working.

 

[Blank88]

Thanks for the responses, I will look into the clutch fan, I know my post isn’t the best description.

I was just using a gauge that comes with the r147a refill kit. I filled it to 40 psi when temp was around 80.I don’t have a way to check high side pressure and low side is maxed on the gauge. Also whenever it stops working and the pressure spikes on low side to above 100, I hear a loud disengage or engage around the fan area and it is it stops blowing cold at that point.

Edit: it also only seems to be problematic when it’s above 95 degrees or above outside.

 

[C420sailor]

Those can gauges are a recipe for disaster. Go to Harbor Freight and pick up a set of the AC manifold gauges. I own two sets, they’re of good quality. They will provide you with significantly better diagnostic value, and you can use them to accurately vacuum down and fill your system after you repair your leak (you have a leak if you need to add…)

 

[Motorhogman]

Good source for troubleshooting AC issues.

AC pressure gauge readings

Learn why normal AC pressure gauge readings are essential for diagnosing car AC problems. Don't rely on just the low-pressure gauge

ricksfreeautorepairadvice.com