First of all let say thanks to all the regular posters on this forum. I am a member of a similar type forum for my archery and bowhunting habit and have to say I could not live without it. I have searched this forum and found what could be many different fixes for my problem. I am like most guys on here,I want to see if I can fix it myself before getting raped at the garage. I have a 98 F-150 XLT with the 4.6 liter motor and it has 233,450 miles on it and the motor runs like it was new. However I have noticed over the past couple of years that my air doesnt get quite as cool as it used to.I had a friend that works on A/C on tractors put some freon in it the other night. When he hooked up the gauges the high side he said was good but the low side was reading 70 and he said that was high. Now I will tell ya this,when at idle the air is just barely cool but at higher RPM's it gets alot cooler. The outside temp was 95 and the air at the vents at idle and max A/C was about 83degrees. At higher rpms it went down to 73 or so but no where close to where it should be. I did have a new heater core put in this truck last winter. From what I have read on hear so far it could be a number of different things from the blend door to a vaccum line to the fan clutch. Does the high number on the low pressure side give off any obvious suggestions??? Thanks in advance for the response to this post and for all you guys and gals that regularly contribute to this site keep up the good work!!!

 

Ya. That's way too high of pressure for R-134a. Hopefully he didn't add R-12 to it.

At 95 deg outside temp. your hi side pressure should be 205-250 psi. Being that your low side is at 70 psi, that will only give you 70 deg. discharge temp at the vents at best! Low side should be 35-40 psi for proper cooling.

Depending on your high side pressure, it sounds like it's overcharged.

 

how did he test it? was it running on max air when he read it if the compressor was not on then you can't tell.

 

thanks for the reply guys!!! Yeh the motor was running and the max a/c was on full bore. The high side was in spec(205-250) but the low side was up around 70 and it did climb when he put in some freon. He was using 134 by the way. It does sound as if its overcharged but I bought the truck 4 years ago and I havent had it recharged. Its a 98 f 150(4.6) and has 233,500 miles on it. Is there any other reasons why the low side would read high other than too much freon?

 

a clog or a bad orifice tube.

 

will check that out!!! thanks