150 is normal for the low side

400 is normal for high side

If your readings arent normal its because you are using propane for your ac recharge. And by the way your containmating your ac recharge machine and supply by using propane....

Cleaning the ac recharge machine is over $1000

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

400/150 are not normal pressure readings.

And somehow I doubt that he used a recharge machine. I did not use one when I recently recharged my 134a system.

He didn't mention it, but of course it is very important to adequately label the system to protect future shops from making a huge mistake.