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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.
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?
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.
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.
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.
Great question-it's a really annoying spot to reach. They finally moved it back to near the expansion valve in mid 1993 when they went to r134a.
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.
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; 03-18-2022 at 10:45 PM.
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.
The pusher fan runs when the system reaches/exceeds a pressure threshold; it doesn't run with the compressor. I think there is a temperature threshold also, but not 100% on that one.
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...
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.
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.
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.
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.
03-18-2022, 07:12 PM
Can't recharge AC
