How do I tell if my truck has AC?

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81GMCSierra

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This might sound like a stupid question but I am just not sure because if it does, it doesn't work. Its a 1981 GMC Sierra 2500, with the 4.8 L6.

The instrument panel in the cab has "A/C" printed on it, but nothing happens when it is selected.

I just got the truck and the previous owner said there wasn't A/C but she really didn't know anything about the truck so might have been mistaken.

There is what looks like a compressor on the passenger side of the engine compartment but I am very new to auto repair and not sure if that's what it is.

The bottom three images in this album are the clues. http://imgur.com/a/nFy7C

Thank for the help. I just want to be sure before buying parts that are particular to whether or not the truck has A/C.
 

RetroC10Sport

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It had an aftermarket A/C unit at some point. It's missing a few pieces though.

Someone replaced the L6 for a small block V8 as well.
 

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No a/c, the blower on the firewall is a non ac model, and you have no compressor on the engine.

Im not sure what that canister is on the blower housing. Maybe some kinda retro ac but if it is, there is nothing else from the system on your truck.

Or and some one might have switched out the heater control at some point.

Or it is some kinda ac gimmick from the factory that I am not aware of. ??? Anyone ???
 

81GMCSierra

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It had an aftermarket A/C unit at some point. It's missing a few pieces though.

Someone replaced the L6 for a small block V8 as well.

Wait... so it doesnt have the L6 in it? How do I tell what engine is in it then?
 

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That's definitely a V8. The truck may have come with a 292 when it left the factory, but a V8 is what it has now.

You will need to see if you can find the engine ID number. It will be on a machined pad under the alternator.

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some times the displacement is printed on the back of the block with the casting numbers.
 

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Here's a visual to help. :waytogo:
 

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The pad behind the alternator is not 100% correct. I maybe but don't go off of that. Block casting behind the drivers head gives you a better idea.

But the difference between a 6 and 8 is big enough same as seeing a AC compressor vs not having one.
 

81GMCSierra

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Here's a visual to help. :waytogo:

Not seeing any numbers, should I climb underneath? Or might I have to take a part of to find it? Other suggestions.

Thanks for everyone's help! This was a surprise to me!
 

RetroC10Sport

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You will likely have to clean off the pad as I'm sure it's covered in a thick layer of grease and grime.

No need to get underneath as it's on top where the block meets the cylinder head. :waytogo:
 

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Not seeing any numbers, should I climb underneath? Or might I have to take a part of to find it? Other suggestions.

Thanks for everyone's help! This was a surprise to me!

NO you wont find anything underneath. Behind the alternator where the head meets the block the block will stick out towards the rad about a half inch, it is a flat shoulder and there are numbers engraved into that shoulder. You often times have to wire brush off the grease and sometimes even the paint to be able to read those numbers. If the block has been rebuilt and they machined the block where the heads sit ( called Decking the block ) you often times will not see the numbers there as the will have been machined off.
 

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The other casting numbers are found behind the drivers side head on the shoulder of the block where the block actually meets the transmission bell housing. Its extremely difficult to see back there while the engine is in the truck due to it being so close to the firewall. And is often caked in oil grease
 

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I just sent you a PM with some links for you to download the 1981 Chevy truck factory service manuals, as well as owners manual and information packets. :waytogo:
 

81GMCSierra

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I just sent you a PM with some links for you to download the 1981 Chevy truck factory service manuals, as well as owners manual and information packets. :waytogo:

Thanks... I just bought some of these online, wish I knew.
 

81GMCSierra

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Still no luck on find what you describe. I found these numbers though...


This was under the air filter round thingy when I took it off...
Firing Order
18438572

And pics of the others... bottom three images are the numbers I found... http://imgur.com/a/nFy7C
 

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