I bought some AC Manifold Gauges! Thoughts on my readings?

[JamesDean]

Hey everyone,

I picked up a set of R12/R134a manifold gauges last week and they came in today.

I decided to check all my MB's with it.

Initial Readings:

Black 420SEL. R12. 80F Ambient.
At idle: 20psi / 150 psi.
1500 rpm: 7 psi / 145 psi.
Temp @ Vents = 55 F on freeway.

Gold 300SD. R12. 80F Ambient.
At idle: 15 psi / 150 psi.
1500 rpm: 5 psi / 150 psi.
Temp @ Vents = 50 F on freeway.

190E. ES-12A/Freeze 12. 80F Ambient
At idle: 30-35 psi / 125 psi.
1500 rpm: 18-20 psi / 125 psi.
Temp @ Vents = 42-45 on freeway.

After these initial measures, I charged up a bit:

Black 420SEL. R12. 80F Ambient.
At idle: 30-35 psi / 200 psi.
1500 rpm: 18 psi / 225 psi.
Temp @ Vents = 55 F on freeway. No change in cooling.
Lots of bubbling at sight glass. Indicates low?

Gold 300SD. R12. 80F Ambient.
Not important. Didnt want to waste rest of R12 can from Black so I put it in here. This car isnt being driven right now.

190E. ES-12A/Freeze 12. 80F Ambient
At idle: 35 psi / 125 psi.
1500 rpm: 20 psi / 125 psi.
Temp @ Vents = 42-45 on freeway.
I added some to the 190, my initial charge of the ES-12 stuff was insufficient, it never kicked on the aux fans so I kept seeing coolant temp spikes. Fixed now.

Just looking for some thoughts on these various pressures and vent temps.
Not looking to spark a refrigerant war. I have stickers on my 190 and other 300SD to indicate that they are NOT R12 in the case they should end up in a mechanics bay. I dont want to ruin their reclamation machines.

The 420 is my main concern, I'm not sure why its not cooling better. I dont want to put any more R12 in it even though the sight glass seems to indicate that it needs more. The high side pressure is at the upper range for R12 at those ambient temps (at least according to charts).

[jeffr0000]

How clean are the condenser and evaporator coils?

[JamesDean]

well I cant speak for the evaporators but the condenser on the 420 looks pretty clean to me..I'll bring out the power washer and give it a good hose down just to cover all bases.

[leathermang]

Tell us the conditions of the test....

[JamesDean]

420 and 300SD were parked in the garage, at op temp, aux fans tripped, box fan aimed at condenser as well. blower set on high. 80F measured in front of condenser. Measured both idle and 1500rpm at these conditions. 300SD didnt get the tripped aux+box fan treatment. Neither did 201.

201 was parked behind 420 just outside of the garage. Still around 80F ambient.

Driving tests were conducted on back roads +40mph and freeway +65mph, 78-80F outside according to the outside temp display.

Not sure what else to describe. Gauges were hung from the hood when testing for pressures.

[leathermang]

Forget the site glass.... not dependable and can give false ' add' indication... very bad... most cars do not even have them anymore due to that... there is a warning in the FSM...

The FSM says to have the blower on low when measuring the vent temperature....your numbers will be lower than what you show and look better in comparison with what others say they get....

[boneheaddoctor]

As leathermang stated....ambient temps before the condenser are needed for these number to mean anything. Pressures vary by temperature, and are referenced to a chart. Would be difficult to get these driving on the highway.

EDIT... I see these were in Post #5.

I would use ALL readings taken with the vehicle in a fixed location all taken at the same time frame.

Lethermang knows his A/C stuff. Trust him.

[Matt L]

You bought one set of gauges to use for two refrigerants?

[boneheaddoctor]

Originally Posted by Matt L

You bought one set of gauges to use for two refrigerants?

Good point....there are WAY different threads on the hoses for the service ports. One can not fit on the other. But the gauges do have scales for two or three different refrigerants. I know the four sets I have do. But typically not R12 AND R134 on the same one....but I'll look tonight to be sure.

[tangofox007]

Originally Posted by boneheaddoctor

Good point....there are WAY different threads on the hoses for the service ports. One can not fit on the other.

There are R-134a couplers that are treaded to fit R-12/22 type hoses. (That doesn't mean that switching back and forth with the same manifold set is a good idea.)

[boneheaddoctor]

Originally Posted by tangofox007

There are R-134a couplers that are treaded to fit R-12/22 type hoses. (That doesn't mean that switching back and forth with the same manifold set is a good idea.)

Haven't seen those....I know mine won't.

[JamesDean]

Heres the set itself: http://atdtools.com/3688
I am aware that 134a uses quick connects vs R12's schrader valves.
I actually haven't used them yet

[tangofox007]

Originally Posted by JamesDean

Heres the set itself: http://atdtools.com/3688

Precisely what I was talking about. Hoses connect directly to standard R-12/22 service valves. Couplers attach to the hoses for R-134a.

Originally Posted by boneheaddoctor

Haven't seen those....

Now you have!

[boneheaddoctor]

If you go to screw them on and they won't ....don't be surprised. I'll will to bet the Guages have scales for both...but the hoses are for R-134 only (that ad has no mention of the couplers working on both). You might need to buy adapters. R-12 hoses won't simply fit the gauges either....the threads are different at the gauge end too.

Curious to know if yours will actually screw down on your schrader valves..I doubt they will if you haven't tried yet. One way to know for sure. I seem to remember the OD of schrader valves being smaller than the ID of the R134 ports.


Edit---- I see they already have the adapters looking closer at the picture.

[JamesDean]

Originally Posted by boneheaddoctor

If you go to screw them on and they won't ....don't be surprised. I'll will to bet the Guages have scales for both...but the hoses are for R-134 only (that ad has no mention of the couplers working on both). You might need to buy adapters. R-12 hoses won't simply fit the gauges either....the threads are different at that end too.

Curious to know if yours will actually screw down on your schrader valves..I doubt they will if you haven't tried yet. One way to know for sure. I seem to remember the OD of schrader valves being smaller than the ID of the R134 ports.

Where do you think I obtained the measurements from post #1?

They screwed down perfectly fine on the schrader valves. I havent used the r134a adapters but I dont see any reason why they wont couple up to the hoses and connect to a quick-connect without a problem.

EDIT: I just attached them, they connect up perfectly fine and seem very robust and industrious.