Tampa 928s

86 I have no center air blowing and there is a buzzing sound in that area; "may be the fan but does not change pitch with speed.

I have hot air coming out of the side vents after the motor warms up.

The air shop said I needed to replace the compressor expansion valve and r/dryer due to non cooling.

I feel this is a vacume leak and the cold air is being overtaken by the hot air .

Although when motor is cold I can feel a little cold air coming from the side vents.

Any feed back please

WallyP

Send me a standard email - techAT928gt.com (change the AT to @) - and I will send you a paper on the 928 HVAC system that should help.

You have vacuum leaks in the HVAC system...

joejoe

Buzzing is from weak relay in control unit. If so comressor will/may not come on. As Walley states you have vacume leaks. If great enough the heater valve will stay in default mode (open). Before replacing expansion and receiver did the shop check pressure? does a/c even work? Seems before they jumped to this conclusion they would haave checked vac operation. It is probably best if you check for the leaks, as many shops would love to learn on your car with varying results. (most of mine were bad) Wally has paper for hvac, when you get it follow it.

SharkSkin

Wally's right, get the vacuum system operating properly -- sounds like your heater valve is not closing, may be other problems as well -- before you sink any money into the refrigeration end of the system.

Tampa 928s

I received Wallys info "thanks" , With the buzzing sound and heat on a leak is evident; it states that without vacuum the heat stays on, go figure I live in Florida ! I guess it's over the river and through the woods with my Mity-Vac
Marry Christmas I'll post on my progress later.
P.S. My box of parts for the Tb/Wp ect ect has arrived All I want for christmas is a little help from Santa to fix all this stuff.

IcemanG17

Dave & Wally have it right, you have at least a couple issues going on.....fix the vacuum first (its cheaper).....then it sounds like an outboard relay to turn on the compressor.....+ maybe a recharge should do it!

carbonfiber

I had that same buzzing sound coming from my 82 928. I removed the HVAC control unit and took the cover apart and cleaned the contacts on the slider and the buzzing went away. You may have the same problem with dirty contacts. The vacuum check valve near the brake master cylinder could be suspect also for the vacuum problem.
JIM
1982 silver 928
200 Arena Red 996