dredpyrt

Every time i get on the throttle it does just as the title says. I seemed to worse at highway speeds than stoplight to stoplight. It has a new Denso rebuilt compressor and receiver but due to unforeseen circumstances we were unable to switch out the expansion valve. Its been converted to r-134 at some point in its life. Thoughts?

bureau13

Is your aux fan (in front of the condenser) working?

bureau13

Actually I'm probably off-base with the fan question...just noticed the part about it being "worse at highway speeds," where airflow over the condenser should not be a problem.

Mrmerlin

have you run a HVAC system vacuum test per Wally's guide?

Please read this link it will fill you in on how things work

https://www.google.com/url?sa=t&rct=...95515949,d.b2w

dredpyrt

No i havent. The guy i take my cars to for a/c service is a good Porsche mechanic and former 928 owner but maybe he missed something. The lowest vent temp he could get was 52 degrees.

joejoe

You are losing vacuum under acceleration causing heater valve to open (default position). As Merlin suggests Wallys' writeup is very instructional. (have used it for all 3 cars)

davek9

^^^^ plus 928 ^^^^

Also have you checked that all the Flap's are working (holding vacuum)?
Have you tested (at the Firewall) Vacuum supply going into the HAVC system, that it can hold Vacuum when you go through the various settings?

Edit: the engine doesn't need to be running using a Miti-Vac (or similar tool) to pull vacuum, however the Key must be on to activate the HVAC system.

Bilal928S4

Sorry, I might be slow, BUT I am reading the OP differently.
If you have a bad/weak battery or an alternator not performing at its prime, THEN the voltage fluctuates with the RPM of the engine. So the blower will run faster with higher RPMs. Typically at cruising speed the RPMs are lower and you might have more problem.
The above is contingent upon the AC system working properly.
HTH

dredpyrt

I have changed both vacuum pods in the dash as they were clearly dead. As far as the battery and charging systems go the battery and alternator are new. A few weeks ago i drove the car a job interview and when i was finished the car wouldnt start. I called AAA and after we jumped it his test equipment showed is was making 13.7 volts but the battery was cooked so dropped in a new Optima. Thanks much for the link to Wally Ps writeup. I know what i will be doing this weekend.

dredpyrt

Let me run this by everbody...How long does it take for a overtightened belt to kill the bearings in a compressor?

Mrmerlin

if your talking about the AC compressor then the pulley is removable,
and a new part could be installed if the old one has a bad bearing.

What info are you using to formulate this question.

dredpyrt

The compressor was new but has been making a alot of noise so i checked the belt tension and it had virtually no deflection. I reset the tension,took it for short drive and still noisy. I popped the hood and took a look at it running and noticed a lot of side to side motion in the belt,almost as if the pulley were crooked. When i had the compressor install done my guy was swamped with work so another mechanic who rents out part of the same shop said he could pitch in to help him out. The guy know his Caddy CTSVs but tensioning a v-belt not so much. Ive been chasing electrical gremlins so were talking maybe 40 miles since i had the A/C serviced.