Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

A/C Pressures

Hello all, I need to “top-off” the refrigerant in my car’s A/C for a bit until I get the time to have my mechanic look for dye stains for the leak. I drive a 2002 Honda Accord with a 4-Cyl engine. Would anyone happen to know what pressure It needs to be filled to (on the low pressure side)? I don’t really trust those color coded diy gauge predetermined pressures. I feel like every car might have a different amount. Thanks!

Note: there is a little sticker with some information, but there is nothing that says pressures. It just tells me amounts in ounces, which is useless to me.

Every car does take a different amount but you can’t go by that b/c you’d need the professional equipment to actually pull down the whole system and then add the amount specified.

I’m not a fan of those DIY refill kits. You’re probably better off just leaving it until you can get a pro to look at it. The issue is really about proper equipment. That said, the low side pressure [u]with the compressor running[/u] should end up being between 25-45psi. Preferably toward the higher side of that. You can’t make this an exact science without the right equipment so don’t try. If you’re going to mess with it, just shoot for the middle of the - probably blue - range on the gauge.

Right, I agree. The reason I would like to top it off to keep it cold is because I do a lot of commuting to and from school. Its often rainy and humid around this time, so I use the A/C to keep my windows as fog free as possible. It takes about 2 weeks for the a/c to lose effectiveness by about 50%. The new diy kits now have a little spinner that you point to the ambient temperature to show you where the pressure needs to be. I still don’t trust it though.

You need a manifold gauge set in order to properly recharge an A/C system. The reason is the high side pressure is more important to monitor and tells the whole story of how the A/C system is functioning over the low side pressure.


The reason you don’t see a recommended pressure is because it’s not that simple anymore. In the Honda FSM, there is a chart that you use to plot the temp and pressure. You have to start with the AC on, inside air, and a thermometer on the floor and the doors open. The you also need a humidity reading from the weather service. Then you go to the chart and plot the high and low side pressures that you should have. With a thermometer in the vent, you should get about a 40? drop.