300SD A/C Charging question
 

I,ve got an 1980 300sd. I bought an adapter kit to charge it with R12A. However, none of the adapters will fit the low-side port. It appears to be a 7/16" flare with a schraeder valve in it. As I peruse my manual it calls for a line connection adapter 7/16" to 1/4". Any idea on a source for an adapter or a work-around? It appears that I could remove the fitting and replace it with 1/4"
but I'm just a little shy on refrigerant and don't want to have to do a full service. Neither of my other 300SD's (both 5-8 months newer) have this large
fitting.
Thanks..

that sounds like it has a R-134 conversion done to it.

Its a quick connect fitting and not a screw on fitting correct?

No, It's a screw on. Just like common r12 fitting except about 1 size larger. The
hi side looks like it's 1/4", but it has a coarser, left hand thread.

hang in there, LarryBible and Leathermang are pros....one of them will have an answer before long....

there are adapters to be had for this.its very common in older cars that you need an adaptor. snapon has alot of them.

If you want to top it off, you best top it off with whats in there now. The left hand threads are to let you know it's NOT R-12, most likely R406A. Use this chart to identify what you have, mixing is not a good idea, or a safe one!

http://www.epa.gov/Ozone/snap/refrigerants/fittlist.html

James

Any chance of a picture of it ?

I believe I've got it figured out. Thanks to all for your help. The EPA link provided by Fishslayer was especially helpful. It looks like I've got Freeze 12 fittings on
it. I'm surprised because I knew that the PO's shop(he's parts mgr at indie MBZ
shop) used freeze 12 but there was no conversion decal on it. PO was pretty
meticulous at record keeping. I also had called my supplier, who sells several
refrigerants(including freeze 12), explained my setup and he acted like he had
never heard of a larger fitting. I"m attaching a photo of some r12 to freeze
12 adapters that look exactly what I've got. Apparently I was wrong about the
initial sizes. It looks like the lo side is 1/2" and the hi side is 7/16". Now that I know what I've got, I'll probably go ahead and drain,evacuate and do a full
recharge with R12a.

I have run into several shops in my area (one of which I highly respected) that are no-longer using r12 and are pushing Freeze12 instead. I think there is so little demand for r12 that the shops find it more economical for them not to have tanks of r12 but to simply get their supplier to send over a few cans of freeze12 which is available locally for 7.99 per can retail.

When I (inocently at the time) allowed the shop to use freeze12 on mine last year, the guy did put a sticker under the hood but did not put the freeze12 fittings on there.

I have just completed my reversion to r12 and am just waiting for the delivery.