Are you knowledgeable about struts? Help needed.

I just received two new rear shocks that I had ordered. They are identical part numbers and visually the same. One shock extends when compressed by hand and the other does not. It has the same resistance as the first strut but simply stays compressed when pushed on. It also has resistance when pulling up on the strut rod. I can hear the fluid inside being squeezed when compressing and pulling on it. Should I return it? I don't want to pay shipping if it's nothing to worry about. It's just seems like one strut is gas filled and the other is a different type. I don't know a lot about shocks and could use some advice. Thanks in advance. 

If they're twin tubes, they really only work when vertical because they rely on gravity to sort out the gas and oil somewhat. I can't remember exactly how this manifests itself, if it would cause a shock not to extend, but it's easy enough to check. Let them sit upright for a while to settle.

In reply to Keith Tanner :

I have no idea what type they are. They are ac delco struts #503-190. They were delivered horizontally in 25° weather so I will let them sit upright inside and see what happens. Thanks for the reply. 

They should be twin tube. Turn them upright and stroke them a few times and see what happens. But that sounds like the opposite of how it should be. The gas pressure is the same regardless of how the damper is oriented, but if it's horizontal and the piston runs out of oil then the actual damping part doesn't work. Temperature is a factor too, just letting them warm up might improve the situation.

That all said, they could still be fine and just very low pressure to begin with. Unfortunately it's kind of hard to get a solid answer without putting them on a dyno.

Sounds like the gas is gone.

Agreed, but they're not dead until they're warm, upright and dead :)

In reply to Pete. (l33t FS) :

So the resistance I'm feeling is the oil in the strut but the lack of it extending on its own is because the gas is gone? 

Should I make an effort to return the strut? It was from an online retailer who does accept returns but I will need to pay the shipping I assume. Or would it be better to just keep it and maybe try to get a few bucks back?

I'd contact the manufacturer to see what they say.

In reply to Keith Tanner :

I purchased them from a retailer on ebay. The struts were from a close out I believe. The retailer offers their own 60 day warranty but I would be out the shipping costs. 

Again it's kind of hard to tell for sure without a dyno. If it's just lacking gas, that's probably not really an issue unless you're going to be really beating on them. But I'd be concerned about what caused the lack of gas pressure. If it was just an assembly error that's one thing, but if there's a damaged seal that's going to allow oil out or dirt in, that's going to cause issues long term. Are they wildly expensive? Honestly I'd probably buy another one and see how it compares and then figure out which to return.

Thanks for all the help. I think I'm going to install it and see how it performs.  I don't beat on the suspension very much. As long as it seems to be working I'll keep an eye on it for any leaks for the next 60 days while I have the warranty. 

If you know how many bad shocks or struts I have pulled out of new boxes...

No gas pressure, valving not connected to the shaft, the works.