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Username Post: A/C clutch turns on and off frequently        (Topic#357268)
Ray1 
Member
Posts: 34

Reg: 12-05-03
07-18-19 12:30 AM - Post#2770959    

A/C is blowing cold and the pressure is on the low side of full. I'm using a guage on the port by the firewall, which I think is the low side? I'm sure there is a slow leak in the system, but I'm reading that this could also be a relay problem. Thoughts? I've been reading around and it seems like this would be a good point to take it to an a/c shop.



 
jktucker92 
Silver Supporting Member
Posts: 308
jktucker92
Loc: West Richland, WA
Reg: 02-05-17
07-18-19 05:03 PM - Post#2771010    
    In response to Ray1

Please post if you solve the problem. Been having a similar issue with my '01 since I bought the truck. Took it to an AC shop and they couldn't find anything wrong.



 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2749
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
07-18-19 07:43 PM - Post#2771024    
    In response to jktucker92

If it is blowing cold then I would not be too concerned.
I would like to know what the pressures are though.
Low low side pressure will kick off the compressor
That would be likely low charge.
High high pressure will cause the compressor to kick off as well.
That is caused by a restriction or high temperature due to air flow restriction.
Does it blow ice cold or just cool?
Just cool likely means it is low on charge.
Normal operating pressures around 25-30 on the low side.
high side is 1.5 times the ambient temperature/
Therefore if it is 80* outside then the high side pressure should be right around 200.


Old School GM fan FOREVER


Edited by rockfangd on 07-18-19 07:45 PM. Reason for edit: No reason given.

 
wagonman100 
Super Senior Member
Posts: 14318
wagonman100
Loc: Baltimore, MD
Reg: 11-27-04
07-21-19 07:00 PM - Post#2771251    
    In response to rockfangd

Sounds like a low charge.

Jay
Friends don’t let friends drive Fords.

1999 Silverado Z71 4X4 extra-cab short bed
1983 Malibu Fauxmad - tubbed
1978 El Camino Kustomized
1972 Monte Carlo
1957 210 handyman wagon
1957 Nomad sport wagon
1957 Cameo Carrier


 
Ray1 
Member
Posts: 34

Reg: 12-05-03
07-21-19 09:56 PM - Post#2771259    
    In response to rockfangd

I put a gauge on the low side, and got a surprise - over the space of a few seconds, the pressure builds from somewhere in the "fill" zone, to 70 psi! Which is in the "danger" zone. Then either the compressor kicks off or a safety valve opens up, and the pressure drops back down into the "fill" zone. It does this over and over again, even if the AC is turned off and the temperature controls are moved into the heat zone. I haven't figured out how to stop it yet (although I haven't spent a lot of time on it either).

It is blowing cool, but not ice cold, air.





 
Ray1 
Member
Posts: 34

Reg: 12-05-03
07-26-19 12:56 PM - Post#2771667    
    In response to Ray1

This seems relevant-

link

In short the problem is probably not the clutch disengaging, but the clutch NOT disengaging, which is going to wreck the whole A/C system. So I've got to pull the power to the clutch and see if it will disengage. Hopefully this will only be a relay or fuse.





 
2plus2 
Member
Posts: 1216

Loc: Mission,BC
Reg: 02-03-05
07-26-19 03:43 PM - Post#2771680    
    In response to Ray1

If the heater is set to defrost it will cycle the ac to dry the air even with the ac turned off

69 Canadian Pontiac 2+2
factory L48 350 Chev,TH350,PW,PT
99 Silverado RCLB 4.8 NV4500 14BSF 4.10's locker 6" Procomp 35 bfg m/t's 9k winch cutout flares
07 Town Car Loaded,Tinted,Getting Bagged


 
wagonman100 
Super Senior Member
Posts: 14318
wagonman100
Loc: Baltimore, MD
Reg: 11-27-04
07-26-19 06:29 PM - Post#2771690    
    In response to 2plus2

Your original post says the clutch is turning on and off frequently, not staying on all the time. Is it stuck on?

Jay
Friends don’t let friends drive Fords.

1999 Silverado Z71 4X4 extra-cab short bed
1983 Malibu Fauxmad - tubbed
1978 El Camino Kustomized
1972 Monte Carlo
1957 210 handyman wagon
1957 Nomad sport wagon
1957 Cameo Carrier


 
Ray1 
Member
Posts: 34

Reg: 12-05-03
07-26-19 10:50 PM - Post#2771703    
    In response to 2plus2

2plus2 - The snowflake button is off. I'm assuming that's defrost.

wagonman100 - I just pulled the plastic panel behind the bumper and looked at the clutch. The clutch is working. My recent theory was that the clutch was stuck on, and I was hearing a safety valve dump the excess pressure, but it is indeed the clutch kicking on and off.

So, here are our symptoms - A/C is cool but not super cold. The clutch kicks in, the pressure climbs from 20-25 psi to 50 psi on the low side, the clutch kicks out and the pressure drops down to 20-25 again. In an earlier post I wrote that the pressure was climbing up to 70 before the clutch kicked off. I'm not seeing that tonight. It's much cooler out now though, for whatever difference that makes.

Could there be a sensor that's gone bad? I'm at a loss on this one as everything appears to be working. If I hadn't been listening for a problem I wouldn't have known there was one.



 
someotherguy 
Senior Moderator
Posts: 29010
someotherguy
Age: 49
Loc: Texas
Reg: 08-01-03
07-27-19 04:50 AM - Post#2771705    
    In response to Ray1

"Snowflake" button is A/C on/off.

Depending on year model, defrost is a function of the knob position (1999-2002), or button (2003-2007 classic.) Defrost symbol is the windshield-ish shape with the three squiggly arrows. If defrost is selected, the A/C compressor will engage as commanded regardless of the A/C button; this is normal operation.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
Ray1 
Member
Posts: 34

Reg: 12-05-03
07-27-19 06:58 PM - Post#2771759    
    In response to someotherguy

Defrost was off.

I believe I've got the problem worked out now. The pressure in the system was too high. After letting off a little pressure, the clutch is staying steadily engaged. The system doesn't seem to want more than 25 psi. That works out to 70 psi with the engine off, which I suppose must be o.k. although it would be in the warning zone with the system working. I saw 100 psi with the engine and a/c off and that was a little alarming, but I guess it is normal for the pressure to be a lot higher with the engine and a/c off. If it isn't, be sure to let me know as I don't need the a/c system exploding on me.

Anyway, this has been a learning experience. I would have assumed the system would like 30-35 psi better than 25, but apparently not.





 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2749
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
07-28-19 08:01 PM - Post#2771860    
    In response to Ray1

If the clutch is disengaged and your low is 70-80 ish that is normal.
As high side pressure decreases it will push the low side pressure higher.
Once the clutch reengages the low pressure should level out and high side should go back up.


Old School GM fan FOREVER


 
Ray1 
Member
Posts: 34

Reg: 12-05-03
07-29-19 04:39 PM - Post#2771951    
    In response to rockfangd

It sounds like everything is o.k. now.

I may have to put a set of gauages that can read both sides on my wish list!



 
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