'94 Chevy S10 Blazer strange A/C problems

My mom owns a '94 Chevy S10 Blazer with 124,000 on it. In overdrive, the air tends to shut down or barely run up hills. If you put it in drive, it usually works better. What's causing this?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The RPM of the engine drives the AC compressor. When in Drive, the RPM of the engine is higher than when in Overdrive, therefore the compressor also cycles a little faster. You might check the drive belt for the compressor to be sure it is within specification for belt deflection....IOW, being tight enough. Also it may be a good idea to check the AC systems' refrigerant charge.
Hope this is of some use.......
Dave S(Texas)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.