Pittsburgh Compression Tester - Harbor Junk

Do not buy this compression tester from harbor freight. It is inaccurate.
I bought this one from Amazon: www.amazon.com/dp/B088RM6JGC?...
In this video I show you the difference between these two testers. Am I doing something wrong with the Pittsburgh?

[@chriscobb4939]

Same thing here then they charge u 20 percent to bring back

[@Ri0tRec0il]

The Harbor Freight Quick Connect Compression Tester is flawed. The one-way valve for the tester is close to the gauge, not inside the end you connect to the spark plug hole.
So when you compress the air, you're compressing the extra volume of air in the hose.
Might not seem like much but throws the accuracy off as you see.
Harbor Freight's other compression tester addresses this issue with a one-way valve in the brass fitting in the hose.

[@newenglandlife978]

If this vid hits a million views we'll give away the crocs!

[@dreamvicious7246]

pretty sure the harbor one reads at half psi because its also meant for heavy equipment, such has skid steers, tractors, semi trucks etc which i would think use higher psi (i could be wrong). where your amazon one is more so directed towards two stroke and four stroke machines would be my logical guess. the harbor one it still reads accurate, just at half psi compared to most common compression testers like the amazon one you bought. but yeah just easier if you get the amazon style one so your reading accurate right away and you dont have to worry.

[@petev.9357]

Make sure the tester you buy has a Schrader valve at the very end that goes into the plug hole. This valve looks like one in a tire but it's not. It's very low pressure like 1.5 lbs. When it goes bad you have to buy special ones for compression testers.

[@steelcityrailroad5095]

I came here because everything I tested with one that I borrowed from a friend came back 50 psi, I was very confused!

[@newenglandlife978]

Scary