On the HB expensive one you cite.... can you give us the model number or sku ?
What counts is the type of vacuum mechanism the unit has .... your post might leave someone to think that once they get one that works properly for its design that it also fills the bill for our AC work... but again, it is dependent on the type mechanism... and I do not believe ANY venturi type can pull the necessary vacuum to do the job effectively.
I got a $340 HF 14 inch band saw on sale for $260 a while back , put link type belt on it , when I started it up I did not even have to track the blade. On the other hand , got a right angle slow speed water grinder and found they had not put any grease into the 90 degree gearbox... works fine now though .

I edited the post, but here it is again for the second page.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=66467

It's a rotary vane design. Pulled down the system we used it on very well, and we ran it for several hours that day.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

Here is an interesting discussion...

http://yarchive.net/ac/vacuum_pumps.html

I would try for a new set of Yellow Jacket or Robinaire Gauges. I would then use the gauages at the local pawn shops in search of a good pump. If they won't let you test for at least a 29.8 vacuum go somewhere else. It is to easy to buy a bad pump (EBAY). I would like to have VSTECH servicing my truck 150 microns is very good.(post 7) Stay away from Harbor Fright (Chicom Crap) Good Luck.

That only happens when the tech is too lazy to pull vacuum for the proper time which is 1 hour or doesnt know how to really to perfom ac service

the snap on vacuum puller is worth the money while the recharge machine for most people isnt really practical

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

It's going to be difficult to stay away from "Chicom Crap" when buying anything new. Four years ago, I bought a set of replacement Yellow Jacket gauges (Didn't need a manifold, because mine is excellent). Guess where they were made?

Of course, they're also excellent gauges, Chinese or not. In fact, I have an easier time finding high quality Chinese tools these days than I do finding high-quality American ones. I'd just give up and buy high-quality German tools, if they weren't so bloody expensive in this country.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

Remember that the max vacuum you can pull is variable... it varies according to barometric pressure.... you may see the figure 29.921 mentioned.... That is the standard pressure... meaning at sea level and a certain temperature. So your immediate weather situation will affect what your vacuum is capable of pulling.
I want a pump which will not be harmed by leaving it on overnight. You just can not be too dry inside an AC system.

ackits.com is based out of phoeniz and has some great starter kits for ac work.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)