Why is my ac so inconsistant? Is there a way to make it colder?

[85_305]

The ac in my PT is SO damn inconsistant. Throughout the day, during one trip the ac will be so cold the grips on my steering wheel are frozen. Then later that day on another trip, the ac will barely even phase the steering wheel..

What gives? This is annoying that sometimes I need to have my ac cranked the whole trip home, and other times on low the ac will suffice.


Also, is there something I can do to make the ac colder and more efficient?

Matt

[GALVANIZEDYANKEE]

It may not seem logical, but when your freon charge gets too low the evaporator gets colder. In fact it will freeze up preventing air to pass. It stays super cold until the evaporator freezes. Have your freon charge checked.
When the freon eventually gets low enough you will get no cold air. Another possibility is that the clutch on your compress is not operating properly.

[85_305]

I'm fairly certain the clutch is operating fine.

So what your saying is I'm low on freon? I have a do it yourself recharge kit, I just need to buy more freon. I usually charge them to the upper spectrum of "full" just to be safe. But why will the ac all of a sudden start pumping out super cold? Could the underhood heat be warming it up or something?

[GALVANIZEDYANKEE]

Automobile AC is not a hermatically sealed unit as is in home AC. The compressor is driven by an external source.
The compressor has end seals that keep the freon from escaping. These seals are not perfect. The have infinately slow leeks. Usually seal loss is not a problem for years. However, eventually enough freon will be lost to effect the AC performance. This is normal.
The charge of you AC is at a precise level, without too much error for under/over filling. Do it your self kits are at best a crap shoot. Proper charging requires: adding a dye to check for leaks, evacuation of the system, recharging with a precision weighed amount of freon, making sure refigerant oil levels are correct.
Automitive AC is not for home shade mechanics. Bite the bullet and find a shop that only works on automotive AC.
If they try to sell you a compressor, get a second opinion.

[bobdole369]

I usually charge them to the upper spectrum of "full" just to be safe.

This is a common mistake. By overcharging - (and the "full" spectrum is simply a guess) - you actually make the A/C work less efficiently.

HVAC basically works like this: compressor compresses freon vapor into the condensor coils where it goes back to liquid. Its quite hot from this and the fan runs to cool that off. Once cooler - it gets to the orifice valve in the evaporator core, where it greatly expands and gets much colder in the process. Your blower motor impels air through those coils to cool your car. However the whole system is more or less sealed. So you have your low side pressure, and your high side pressure. If the low side pressure is slightly higher than stock - that means there is less room for the freon to expand. It will only serve to increase high side pressure as well. Normally the system cycles by getting to a low pressure point. Oftentimes with too much freon that never happens and instead the high pressure is tripped. The user checks with a gauge - its within the "full" section so they are lost.

By adding more freon than specified - you are actually reducing the cooling effect of the system.

In addition most home refill kits only check low pressure and are only a ballpark figure. Those pressure gauges are CHEAP!

A proper HVAC mech will have both gauges and will know to adjust for temperature changes as well as the temp of the engine bay.

I don't recall the number off the top of my head but you can find it in the service manual linked at the top of this forum. I recall that on my own "refill kit" that the actual pressure specified in the manual was in the "recharge" segment of the gauge.

So if you must do it yourself, borrow a set of gauges that actually work, and read the manual for the proper pressures. Don't trust that bottle gauge at all.

[85_305]

Good information.. thank you. How much would a shop charge for all this? Probably quite a bit...