I'm Sweating!
 

Well, I was in Mexico all of last week, but that is not why I am sweating.

On the way to work this morning I had constant hot air blowing from my vents!

My first thought was my monovalve gave up after 25 years. Is this the only or just the likely culprit?

From my searches, it seems rebuilding is the way to go. Any recommendations? Or is my recollection of previous readings faulty and it is not the monovalve causing my constant heat?

tia,

Tim

mine does the same thing and it's because I ain't got no freon in it
I wish it were the monovalve

I would check your valve by applying 12 v directly to the terminals to see if you stop the hot air.

I had the same problem, but it turned out to be my CCU that had gone bad, not tell the monovalve to shut off, giving me hot air all of the time.

My 95 actually shuts down as the high pressure side gets too much psi if its 90+ or if I redline the motor.

You mention "hot air" coming from the vents.

Are you speaking of ambient air that has been cooked by the sun in the intake plenum? The temperature of the air coming out of the vents when initially started in the sun can be significantly higher than ambient.

After you drive the vehicle for awhile, does the air temperature from the vents get back close to ambient?

Or, are you positive that the air temperature from the vents remains well above ambient...........for an unlimited time?

This is not a trivial question. You might be chasing a monovalve when it has nothing to do with the issue.

Brian

I left for work at 0600 and ambient was about 75F. The air coming out of the vents was at least 130F and didn't quit until I turned the system completely off.

A/C was converted to R134A 2 years and 15,000 miles ago and was blowing ice cold when I left for Mexico (I usually have to set the temp wheel near the white and red zone interface to keep from freezing if ambient is below 90F). The car sat in the garage unmolested while I was gone.

Thanks!

Tim

OK, that seems to indicate a faulty monovalve. First thing I'd do is to pull the monovalve diaphragm and see if there is a tear in the rubber. That's the most common failure.

If that's good, see if the monovalve will cycle if you apply and remove 12V and ground from it. You'll hear the solenoid make a "thunk" if it's working properly.

If that's good, then see if there is a ground signal from the CCU at the monovalve. That's how it closes.

If no ground signal is present, then run two jumper wires to the monovalve.......one from ground and one from 12V. Now take it for a drive and see what you get.

If it works properly and you have a/c, the CCU is NG.

monovalve diaphragm
 

It is easy to get to the monovalve diaphragm, there are four screws on the top of the monovalve. Pull to solenoid and you check for torn rubber and endure the solenoid slug is free to move about.

Jim

I had a fuse once break on me, and consequently received a face full of hot air. Replaced the fuse, and counted myself lucky!
There should be a pictoria somewhere on this site - or a link to one, as to how to replace a mono valve. It's pretty simple - just make sure you don't let the any parts fall off the stem, so you know how to put it back in.

Thanks guys!

I will certainly check this all out at the first opportunity. I was sweating like a hog on the way home from the office today!

check/roll the fuses

Fuses are all good (darn!).

Monovalve rebuild kit should be in from Fastlane tomorrow.

The drive home in sunny 93F and high humidity was really fun today!

I took the lazy way out and installed a new monovalve last night. I figured even if it isn't the valve, that puppy will be giving up soon enough regardless.

I was worried when I pulled the old valve and the diaphram was intact. Fortunately, the new valve did the trick as I am back to normal now.

I guess I'll never know exactly what the failure mode was. That's what I get for being lazy ;)

Thanks for all the responses,


Tim