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  #1  
Old 06-02-2010, 12:19 AM
showme's Avatar
Mama's 300D
 
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Question on 300d's automatic air problem

My wife's ac hasn't been acting right lately, so I'll run it by you guys and see what you think. When we turn on the vent or ac to cool (it's an auto), it's been waiting a few minutes, then kicking on a mile or two down the road. It runs a few seconds, then shuts off. The only time it seems like it stays on is in the evening when it's cooled off outside. Is there a sensor in the dash? Could it be a loose wire? Would a low freon (I know) charge do that? I pulled the console up a month or two ago to change the radio. I've even started pricing new units. Opinions, please.

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  #2  
Old 06-02-2010, 11:11 AM
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mmmmmm Diesel...
 
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In auto mode, the fan starts slow and builds up. Check the resistor pack, as it is under the hood, and needs good ground.

The compressor should engage immediately when the center button is pushed. Low freon wil either not kick on, or will cycle.

My car is an '82. Did the '81 still use the servo set up?
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  #3  
Old 06-02-2010, 12:09 PM
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The push button units are known to produce odd symptoms, a cold solder will give you all sorts of strangeness. If you decide to check there, you're going to have to remove it to inspect.
If, however, you have the dreaded servo unit, (vertical push button unit) all bets are off.
The 82's, I believe, have the horizontal push button unit, that is the one I referred to at first.
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  #4  
Old 06-02-2010, 12:10 PM
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I'm not sure what you mean by servo set up. It has a wheel type adjustment for temp, and a button with "high", "low" and Automatic. It won't even blow (until it's ready, and then for only as long as it wants) when it's set on high or low. But it does come on sometimes. It may be a ground problem. It's just really weird.
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***********************************


1951 Chevy 3100

2003 Indian Chief Roadmaster

1983 GMC 1 ton Dually

1982 Chevy 1 ton Dually, service body (sold)

'90 GMC Suburban 6.2 "SS Veg-Burban"
(single tank WVO\diesel conversion) SOLD

'81 300D ~ Mama's car...my job (now my car)(but still my job) SOLD

'83 300sd ~ rescue car SOLD

2005 Ford Taurus (Mama's new car)(NOT my job!)
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  #5  
Old 06-02-2010, 12:22 PM
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The 81 300D does NOT have the servo II setup.

The 81 300D climate control is just like the 82 and above like the SD too.

My underhood experience on both was that the 81 has the newer climate control
but still had the older style cruise control, and non-turbo motor.

So the 81 is a change-over year , sort of a hybrid.
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  #6  
Old 06-02-2010, 12:32 PM
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^ Agreed, 81 was a, well, hybrid is a nice word for it.
The servo unit, circled, is under hood.
The vertical push button unit (CCU) is associated with it, second pic.
The horizontal push button unit (CCU), third pic, is the later style, no servo, but a mono valve that fits in item #119, fourth pic.
Attached Thumbnails
Question on 300d's automatic air problem-servo-circled.jpg   Question on 300d's automatic air problem-ccus-003.jpg   Question on 300d's automatic air problem-ccus-004.jpg   Question on 300d's automatic air problem-mono-valve-circled.jpg  
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  #7  
Old 06-02-2010, 02:07 PM
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Yep, mine is the horizontal, and I've changed the control valve twice since we bought it. (The second time as a "possible" fix, which it wasn't the problem.) So I'm going to start by just trying to add some refrigerant, but when I checked it last year, it showed the pressure was in the red, but it wasn't cooling well. I may need to have it vacuumed down and refilled. That worked on my old truck once. Are there any of the vacuum check valves in this system that may be not funtioning that would cause this?

Somebody had mentioned the cold solder on something(?) I really hate to start digging behind the dash, for fear of screwing something else up while trying to fix the AC. But it's been 90*here in Missouri the last week, and the DW says it needs to be fixed. All comments are appreciated!
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***********************************


1951 Chevy 3100

2003 Indian Chief Roadmaster

1983 GMC 1 ton Dually

1982 Chevy 1 ton Dually, service body (sold)

'90 GMC Suburban 6.2 "SS Veg-Burban"
(single tank WVO\diesel conversion) SOLD

'81 300D ~ Mama's car...my job (now my car)(but still my job) SOLD

'83 300sd ~ rescue car SOLD

2005 Ford Taurus (Mama's new car)(NOT my job!)
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  #8  
Old 06-02-2010, 03:20 PM
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There is a sensor which has a foam pipe behind the glove box, at least if said sensor is in the center of the dash, a square grill. It has been known to deteriorate. That would give you false temperature readings causing the A/C to act odd, temp wise. If you're low on freon, you won't get cold air.
There is a long procedure to test for proper vacuum operation, at least a function diagram. What vents are open when you turn on the A/C? Check your owners manual for what is supposed to be open.
Yet one of the problems you mention is a delayed action once the button is pressed. If there is a vac leak in the HVAC somewhere, you may experience this, but a cold solder, see pic, can cause the same thing. That would be on the printed circuit board of the CCU. A cold solder can cause the wrong flaps to open.
Attached Thumbnails
Question on 300d's automatic air problem-cold-solder.jpg  
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  #9  
Old 06-03-2010, 09:55 AM
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Thanks, too many! I appreciate that. I've always wondered where the sensor was at. And thanks for the clarification on the cold solder. I just bought a mighty vac not too long ago, and it's time I start getting used to it. I think I'll go over the whole thing. But I appreciate the pic of the board and also your diagrams before. A picture is worth a thousand words! Thanks again to all of you. Anyone else who has any info or tips, I would really appreciate hearing from you.
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***********************************


1951 Chevy 3100

2003 Indian Chief Roadmaster

1983 GMC 1 ton Dually

1982 Chevy 1 ton Dually, service body (sold)

'90 GMC Suburban 6.2 "SS Veg-Burban"
(single tank WVO\diesel conversion) SOLD

'81 300D ~ Mama's car...my job (now my car)(but still my job) SOLD

'83 300sd ~ rescue car SOLD

2005 Ford Taurus (Mama's new car)(NOT my job!)
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  #10  
Old 06-03-2010, 09:25 PM
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You're welcome.
Someone once said, "finding the problem is 50% of the fix", I agree.
A mity-vac is essential, yet checking each individual pod can be onerous at best, as you need to access each one, start by removing the glove box, or what ever pod is not opening when it should.
Keep us posted.
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  #11  
Old 06-03-2010, 09:44 PM
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Does it do it on all settings or just cooling? It sounds like it could be the blower brushes on their way out.
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  #12  
Old 06-04-2010, 10:21 AM
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^ That's possible too, usually when that happens the fuse routinely blows, as the motor is pulling too much amperage.

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