My99

Can anyone tell me which line it is that's the high pressure, versus which line is the low pressure on a 90 model? It seems that the caps are both the same color.

Yoda

The hi side is the one that is in the hose from the compressor to the condensor (radiator), the low side is on the hose fom the evaporator (inside the cab) to the compressor.

If you don't know, why are you working on your AC? It should use R12, which is not avail for home use.

My99

I don't know, thus I'm asking. I'm working on it because I don't think an air-conditioning system takes a special degree of some sort to work on it. I think I can figure it out with a little help here. Thanks.

98 Joes

Let's see if I can explain this. The low side fitting on my '94 is the nearest to the firewall and kinda tucked under some hoses. At least on mine, the Low cap has a 'L' on it and the High has a 'H' on it, but that doesn't mean yours will.

My99

Mine didn't. I guessed right then! Thanks so much! Just wanted to make sure. I just couldn't imagine why they would make the low pressure line harder to get to than the high pressure line. Thanks again.

Mohamed

I'm not trying to be mean but I agree with David, A/C systems require special vaccums and pumps to properly evacuate a system, boil the moisture out (by pulling a vaccum), and recharging with the proper amount (especially with refrigerant oil). Sure there are the DIY'ers, but then I have never seen a DIY'er work as well as if it is properly done...just a thought.

Oh by the way, another good way of telling which is the low side line is it will be the bigger of the two, and high side will always be the smaller of the two (In regards to diameter thickness of the line), this is always the case as I have seen. In fact some a/c systems come with both black caps on the high and low side fittings (especially in newer systems) so that method mentioned is the only way to find out which side is which (besides looking it up in a manual).

98 Joes

Absolutely agree. If you can, get the system evacuated with vacumn. I'm lucky, I have a buddy who own a shop and he did the prep stuff for me. All I did was fill it with right amount of refrigerant. Most shops that do A/C will evacuate it for you for around $20. Please try not to open the valve and vent to the air. You might even try a repair school. They might do the whole thing for you for student experience.