Can't recharge AC
Thread Starter
Racer
Joined: Jun 2018
Posts: 371
Likes: 38
Can't recharge AC
It's that time of the year and I haven't ever used the AC on my 928 since I just fixed it from sitting in the grass for 15 years and I'm trying to get the AC working. I hooked up my gauges to the high and low side, which I assume the high side is under the upper radiator hose and vacuumed it out with it holding vacuum to my surprise. At least for an hour it did. So I put a little oil in the tube thing and ran the engine with the AC on to fill it with R134a and it took nothing. I shut off the high side and tried to let in refrigerant and nothing. I'm no AC expert so any advice? It's a 1985 928.
Drifting
Joined: Oct 2010
Posts: 2,266
Likes: 630
From: Centerburg, OH
You assume wrong. High side (red) is in front left of the radiator. Low side (blue) is under the top radiator hose. I’m surprised you could get the high side fitting on the low side line. You also have to have enough Freon pressure to kick the compressor on. Did you do a r134 conversion with the newer fittings without taking out the R12 Schrader valves out of the lines?
Archive Gatekeeper
Rennlist Member
Rennlist Member
Joined: Sep 2002
Posts: 18,813
Likes: 4,011
From: Irvine, CA
If you opened the actual high side from the compressor to the bottle of freon while the motor was running, you're lucky the bottle didn't explode, that scenario is dangerous. If the system was initially completely empty and you didn't have the low pressure switch jumpered, most likely the compressor wasn't actually turning. Or was it? Post some pics of where you've got hoses connected.
Thread Starter
Racer
Joined: Jun 2018
Posts: 371
Likes: 38
If you opened the actual high side from the compressor to the bottle of freon while the motor was running, you're lucky the bottle didn't explode, that scenario is dangerous. If the system was initially completely empty and you didn't have the low pressure switch jumpered, most likely the compressor wasn't actually turning. Or was it? Post some pics of where you've got hoses connected.
Archive Gatekeeper
Rennlist Member
Rennlist Member
Joined: Sep 2002
Posts: 18,813
Likes: 4,011
From: Irvine, CA
Also why did Porsche put the low side in the hardest place to access?
Thread Starter
Racer
Joined: Jun 2018
Posts: 371
Likes: 38
That's why I assumed the one to the front of the engine bay that's easy to access was the low side because that made sense. That's how it is in most cars.
Trending Topics
Archive Gatekeeper
Rennlist Member
Rennlist Member
Joined: Sep 2002
Posts: 18,813
Likes: 4,011
From: Irvine, CA
Perfectly reasonable assumption!
For what it's worth, another way to charge a completely discharged system is with the engine off, and you can fill the system through either the high or low side (doesn't matter) by weight. Works best with a 30 lb jug of freon so you're not potentially introducing air while switching cans, but 3 to 3.5 12-oz cans will get you pretty close. After filling, wait 10-15 minutes to allow the freon to flash so you don't potentially hydrolock the compressor.
For what it's worth, another way to charge a completely discharged system is with the engine off, and you can fill the system through either the high or low side (doesn't matter) by weight. Works best with a 30 lb jug of freon so you're not potentially introducing air while switching cans, but 3 to 3.5 12-oz cans will get you pretty close. After filling, wait 10-15 minutes to allow the freon to flash so you don't potentially hydrolock the compressor.
Last edited by Rob Edwards; Mar 18, 2022 at 10:45 PM.
Rennlist Stories
The Best Porsche Posts for Porsche Enthusiasts
9 Features and Characteristics That Only Porsche People Understand
Verdad Gallardo
I've Written 500 Rennlist Articles: Here's How Porsche Has Changed Along the Way
Joe Kucinski
10 Most Unnecessary Porsches Ever Built (And Why We Love Them)
Verdad Gallardo
Porsche 911 GT3 S/C vs 718 Spyder RS: 10 Categories, One Winner
Joe Kucinski
This Builder Is Turning Heads With Its Slantnose 911 Creation
Verdad Gallardo
Porsche 911 GT3 Artisan Edition Pays Homage to Japanese Culture
Verdad Gallardo
Porsche Reveals Coupe Variant of the Electric Cayenne With a Fresh Look
Verdad Gallardo
10 Porsche Colors That Have More Personality Than Most People
Verdad Gallardo
Guntherwerks' Final Speedster Creation Is the Ultimate Porsche Restomod
Verdad Gallardo
Rennlist Member
Joined: Feb 2012
Posts: 1,431
Likes: 215
From: Under Cruella's Thumb
Good news is that I failed twice. Not only did I hook up the low side wrong but the Freon container wasn't even opened. I was able to get about 12oz of 134a in there and the compressor did kick on and started to blow a little cold. I will put more Freon in the system but I noticed the fan isn't kicking on. That is concerning. Also why did Porsche put the low side in the hardest place to access? Burned my hand a few times getting to it. Left the cap off to put back on when the engine cooled down.
There is also an after-engine cooling circuit that runs the current through a 6v ceramic resistor to operate the fan at half speed when the temperature switch (that thingy screwed into the front of the intake there) closes when the engine is switched off... be aware the connection at that switch is always energized when the car is off...be careful around it.
And yes, I don't have a good way of not burning myself either when charging it up...lots of yelling and cursing every time I give myself a nice 2nd degree...
Last edited by 928NOOBIE; Mar 18, 2022 at 10:49 PM.
Three Wheelin'
Joined: Dec 2008
Posts: 1,306
Likes: 558
This extension to the low side port has worked great for me with no leaks: https://rennlist.com/forums/928-foru...extension.html
Nordschleife Master
Joined: May 2012
Posts: 5,234
Likes: 437
From: Thousand Oaks California
I just filled my 85 with R12. I had to get a special thread chaser for the old R12 fittings as the ones on the car were fill with crap and a little damaged.
Probably due to ham fisted mechanics trying to get hoses onto them.
As for the fan, it is purely temperature controlled. One sensor is in the lower right side (facing the front of the car) of the radiator and turns the fan on if the coolant gets hot. (this sensor fails often)
The other sensor is on the receiver opposite the high side port, this sensor rarely fails in my experience, and it turns the fan on when the freon gets hot.
Probably due to ham fisted mechanics trying to get hoses onto them.
As for the fan, it is purely temperature controlled. One sensor is in the lower right side (facing the front of the car) of the radiator and turns the fan on if the coolant gets hot. (this sensor fails often)
The other sensor is on the receiver opposite the high side port, this sensor rarely fails in my experience, and it turns the fan on when the freon gets hot.
Nordschleife Master
Joined: May 2012
Posts: 5,234
Likes: 437
From: Thousand Oaks California
^^ If your high is similar to your low side fittings like in your pictures, you're using R134 fittings on an R12 system.
It's generally not looked upon favorably as the whole point of those fittings is to prevent cross contamination of different refrigerants.
So shops would flat out reject anyone with a setup like that for legal and liability reasons.
But if it's just you who does the servicing it'll never get the wrong stuff put in
It's generally not looked upon favorably as the whole point of those fittings is to prevent cross contamination of different refrigerants.
So shops would flat out reject anyone with a setup like that for legal and liability reasons.
But if it's just you who does the servicing it'll never get the wrong stuff put in
Thread Starter
Racer
Joined: Jun 2018
Posts: 371
Likes: 38
The AC seems charged and working now but the radiator fan doesn't come on when I have AC on. Is that normal? Usually in most cars the fan kicks on immediately when the AC is on. I can confirm the fan does work when the engine is hot.
Rennlist Member
Joined: Jun 2005
Posts: 10,578
Likes: 1,030
From: Oman
As I am aware you have a mechanical fan with an auxiliary electric fan. The electric fan is ddriven by a temperature switch on front driver side of your radiator- that looks at the temperature of the coolant and its set point is reached it kicks in to ry and cool things off a bit but basically it does not give a toss about the ac system. It's intent is to help keep things in check when stuck in slow moving traffic and the air flow is low to non existent.