Automotive Air Conditioning Information Forum

Hello all

I have a converted my 1989 BMW 325i to R134a (compressor, expansion valve, dryer switch, condenser, lines, oil etc) and recently found a leak at the R134a suction port adapter. These adapters are widely available and often seem like not so well made items. Some are steel some are alum. Some leave the existing shraeder valve in place some do not.

When I replace it I am wondering:

1. Any suggestions for the "best" adapter? Its a small item so cost is no object.

2. Besides idiot proofing, is the adapter strictly speaking necessary? I have a manifold set, can I not charge the system without any R134a adapter whatsoever?

r-mm wrote:2. Besides idiot proofing, is the adapter strictly speaking necessary? I have a manifold set, can I not charge the system without any R134a adapter whatsoever?

Technically, I see no reason why one couldn't charge R134a through an R-12 low side service port. While I think this could make it confusing for a future mechanic, don't see why you couldn't do this.

Of course, there may be some regulation against doing this. One is supposed to put a sticker under the hood stating that the system has been converted to R134a anyway.

Fully understood - I already have the car clearly labeled underhood and in my service records that'll go to the next enthusiast who owns the car.

Since I never worked on an R12 equipped car can you clarify how the connection to the low side is typically made? Is it simply threaded on as shown, omitting the Quick Disconnect? I am using the HF manifold: https://www.harborfreight.com/AC-R134A- ... 62707.html

Answer appears to be: yes this works.


When charging R12 is there any means of stopping the remaining refrigerant in the manifold hose from discharging to atmosphere when you unthread it from the suction port?

r-mm wrote:Answer appears to be: yes this works.


When charging R12 is there any means of stopping the remaining refrigerant in the manifold hose from discharging to atmosphere when you unthread it from the suction port?

Not without a low loss adaptor that shuts the hose off. Harbor Freight is like a Nest thermostat....garbage

I agree that you can technically charge R-134a using the vehicle's existing R-12 connections. But your HF manifold gauge set appears to have Acme fittings on the ends of the hoses that aren't compatible with the R-12 threaded connections. So you'll need some kind of adapters to make the transition. Yes, the R-12 hoses do screw on as your picture shows..

I forgot to mention that whatever adapters you use must have depressors in them that press down on and open the Shrader valves so that you can access the system.

The HF manifold set has R12 threaded connections with depressors prior to the quick disconnects. Per my photo they thread onto the existing R12 service ports. I successfully charged the system using this method.

Was not aware of the low loss adapter thanks for that.

Actually ALL hoses must have a low loss fitting at it's end.

Good deal. Glad you got it charged.