The 510 valve has been gone for years.  I used to buy the 620 valve, swap NEW guts into 510 valve, but the 620 valve now gone.  Only valve I know of still available thru Nissan is the 240Z, which I know that I can swap the NEW guts out of.  I do NOT know if the 720 has the same "guts", but I would GUESS yes.  If it does, that might be your best bet.......buy NEW, swap guts!  The valve bodies themselves generally don't go bad, it's the plastic pieces & rubber seals INSIDE that do!  Can you get your hands on a old crusty 510 620 or 240Z valve so you can see if the "guts" are the same, before you go buy a NEW 240Z valve??

TJ

Madkaw 616

Posted June 5, 2019

The 720 I had was a very simple in line plastic one.

Madkaw 616

Posted June 5, 2019

I just abandoned my entire heat and a/c system that all worked as they should prior to installing a re manufactured long block Z24 on my 1985 ( built in 4/1985 so compatible with all other US 1983-1985 720's) My truck is a 4x4 standard cab short bed CA emissions model but I wouldn't think any details that specific would pose a compatibility issue. I dont recognize this part, where is it located?

Madkaw 616

Posted June 5, 2019