At last, AC upgraded more properly.....
05-27-2018, 06:03 PM
#16
I would not use the Prius, I'd use a digital thermometer and observe near the front bumper. But for ****s and giggles lets say its near ambient.
Can't say your estimate of charge reads easily but let's say you added 6 oz.
If you purchased a "Denso" in a Denso box, they usually do ship with oil, but we never trust it and dump it out.
And if you did purchase a Denso in the box, the oil is not R134a oil, hence why you dump it out.
But anyway, you got plenty of oil in the system, can't say long term how it will do, but you have oil.
And, its very normal to have some oil **** out of the service port when you disconnect your service hose.
AC stickers are not usually on the door, things line VIn Id plates and tire pressures are on doors.
If you search google images for sharks you can find stickers and where they are located.
A 2 evaporator system on a shark of 87-89 vintage Porsche suggested 1030 grams or 36 oz of R134a. So maybe my previous estimate of R12 was not too far off.
You might have 24+6 or 30 max, depending upon whether you used refrigerant to purge the air from your service lines; unless you pulled a vacuum on them and
tried to swap over the vacuum/refrigerant line to the can... anyway...
Dual evaporator 928's typically see the front vent temp rise when you turn on the rear air; mine use to rise 10F. I could never balance
my 6 pack of Beck's on the rear console of my previous Sharks and my lobster's preferred the glove box, so I never turned on rear air.
Sweating driers? That would be an indication of expansion happening before it was suppose to happen.
Drier should be warm to hot when the system is operating.
Sweating should be occurring at your TEV's on the evaporator outlet side and at the compressor suction line.
50/210 difficult to comment on because I can't tell if that reading was immediately after you added refrigerant or some time later,
as you want things to settle down after charging.
And, can't comment on 45/220 because of the same consideration; you need to let things settle down after revin the engin.
Turning off the engine and noting 70/200 does not help, readings are best taken at idle, clutch engaged.
If you want to check the 'static' charge you do it when the system is cold or wait 20 minutes after you turn it off,
it can take some time for the sides to equalize.
However, if you have 30 oz (factually) in the system then you are short about 20% or 6 oz.
Toss your gauges back on, let the system run for 10 minutes, take some readings at idle (along with known F readings near the front bumper),
write them down. Try to add 6 oz refrigerant. Let the system run for 10 minutes after you do that document your pressures and temperatures
at idle again.
And, Porsche does have a procedure for all of this, although not as well documented and the equipment is
unique of sorts. Usually its in section 87 of the 928 Shop Manual collection.
Can't say your estimate of charge reads easily but let's say you added 6 oz.
If you purchased a "Denso" in a Denso box, they usually do ship with oil, but we never trust it and dump it out.
And if you did purchase a Denso in the box, the oil is not R134a oil, hence why you dump it out.
But anyway, you got plenty of oil in the system, can't say long term how it will do, but you have oil.
And, its very normal to have some oil **** out of the service port when you disconnect your service hose.
AC stickers are not usually on the door, things line VIn Id plates and tire pressures are on doors.
If you search google images for sharks you can find stickers and where they are located.
A 2 evaporator system on a shark of 87-89 vintage Porsche suggested 1030 grams or 36 oz of R134a. So maybe my previous estimate of R12 was not too far off.
You might have 24+6 or 30 max, depending upon whether you used refrigerant to purge the air from your service lines; unless you pulled a vacuum on them and
tried to swap over the vacuum/refrigerant line to the can... anyway...
Dual evaporator 928's typically see the front vent temp rise when you turn on the rear air; mine use to rise 10F. I could never balance
my 6 pack of Beck's on the rear console of my previous Sharks and my lobster's preferred the glove box, so I never turned on rear air.
Sweating driers? That would be an indication of expansion happening before it was suppose to happen.
Drier should be warm to hot when the system is operating.
Sweating should be occurring at your TEV's on the evaporator outlet side and at the compressor suction line.
50/210 difficult to comment on because I can't tell if that reading was immediately after you added refrigerant or some time later,
as you want things to settle down after charging.
And, can't comment on 45/220 because of the same consideration; you need to let things settle down after revin the engin.
Turning off the engine and noting 70/200 does not help, readings are best taken at idle, clutch engaged.
If you want to check the 'static' charge you do it when the system is cold or wait 20 minutes after you turn it off,
it can take some time for the sides to equalize.
However, if you have 30 oz (factually) in the system then you are short about 20% or 6 oz.
Toss your gauges back on, let the system run for 10 minutes, take some readings at idle (along with known F readings near the front bumper),
write them down. Try to add 6 oz refrigerant. Let the system run for 10 minutes after you do that document your pressures and temperatures
at idle again.
And, Porsche does have a procedure for all of this, although not as well documented and the equipment is
unique of sorts. Usually its in section 87 of the 928 Shop Manual collection.
Last edited by griffiths; 05-27-2018 at 07:02 PM. Reason: key boarddups
05-27-2018, 07:58 PM
#17
Chronic Tool Dropper
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Fwiw, my R134a conversion ‘89 shows 30 psi low side with engine at 1500 rpm, fan on speed 2. More takes high side pressure above200 at 80 ambient. You goal is the lowest possible suction pressures while delivering liquid to the expansion valve. More raise the boiling point in the evaporator, so less heat is carried from the cabin. As Griff mentioned, your pressures are a bit higher than ideal. Don’t add any more refrigerant.
05-31-2018, 07:05 PM
#18
Rennlist Member
Thread Starter
So the droplets on the condenser were oil droplets, not water and were from the spurt of oil from the high pressure port. On the bad side, I do probably have 3 oz of mineral oil from the compressor (note to self: Always drain new compressors and put real oil in) but since I'm using double capped oil it should be ok for a few months until I get under there, drop the compressor, drain it, flush the whole thing AGAIN, etc....
The front fan was not working properly, problem was the happy PO had shoved a copper shim into fuse 29 to power his booster or heck knows what. As a result, I had to remove the plastic fuse frame for 26-30, clean them all, use new fuses, snug the pins closed (the fan one was spread wide, and the headlamp motor/control one was also spread) and put everything back together. Should work better now, I'll get in there with a IR temp sensor and check for any hot fuses or relays.
In the meantime we got *DUMPED* with rain. Granted our town wasn't destroyed like Ellicott City (what a shame) but it was a mess. And since then it's been in the 70/80's with 100% humidity so any AC system would work fine. I'll have to retest it again when it warms up, meantime it works fine. I did add the final 6 oz of R134a and got pressures of about 50/260 at 85F. Will check it again in a week or two to see how it looks.
C
The front fan was not working properly, problem was the happy PO had shoved a copper shim into fuse 29 to power his booster or heck knows what. As a result, I had to remove the plastic fuse frame for 26-30, clean them all, use new fuses, snug the pins closed (the fan one was spread wide, and the headlamp motor/control one was also spread) and put everything back together. Should work better now, I'll get in there with a IR temp sensor and check for any hot fuses or relays.
In the meantime we got *DUMPED* with rain. Granted our town wasn't destroyed like Ellicott City (what a shame) but it was a mess. And since then it's been in the 70/80's with 100% humidity so any AC system would work fine. I'll have to retest it again when it warms up, meantime it works fine. I did add the final 6 oz of R134a and got pressures of about 50/260 at 85F. Will check it again in a week or two to see how it looks.
C
06-01-2018, 02:49 PM
#19
Rennlist Member
Thread Starter
Interesting issue: The AC is working pretty well, however on these warm wet days (1000% humidity) if I drive the car, stop for gas, then start up again the AC doesn't work for about 10 minutes. I think the evaporator is icing up on shutdown, granted it is completely humid here, but interesting.
C
C
06-01-2018, 05:09 PM
#21
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Thread Starter
C
06-01-2018, 08:39 PM
#23
Rennlist Member
Thread Starter
Pulled the drain pan and gasket and checked the freeze switch. It's not that. However I have figured out what it is; the AC compressor does not always come on when you press the AC switch. Because (drumroll) the relay in the head unit stinks. Granted I popped the top on it and cleaned/checked the contacts a few months ago but my guess is that there was a massive shortage of copper when they built the 928's and as a result they undersized every damn wire and connection :-)
Fortunately there's a solution: Yes I could hand wire in a DPDT relay at the head unit, but I didn't want to do that and have a relay hanging off the side. So although that relay is too weak to handle a 3a inductive load (checked with the amp meter, it's 3a on the dot) I went with a better idea.
What I did was take a nice 30a automotive relay, SPST and wire it in under the drain pan. The wiring was as follows:
Wire from the head unit goes to one side of the relay coil, the other side of the relay coil goes to the freeze sensor. The other wire from the freeze sensor then goes to ground on the driver's side fender through the grommet. This means that the relay in the head unit now only has to switch 150ma or so instead of 3a of inductive power (which will spark/arc when opened so it's a mess).
The wire going to the compressor goes to one of the SPST contacts. The other side goes to a 12 gauge wire which goes to a 5a fuse, which goes to B+. Problem is there are not a lot of places for B+ to tap into however there is one that is always on, 12v, and has a 20a fuse on it. And it's easily accessible.
Yes, I am talking about the fan overtemp switch on the front of the intake manifold. I built a wire that plugs into the manifold switch, then goes to the +12 line via a short plug with an insulated connector, then a long wire that goes to the fuse, then the relay's other SPST contact.
Result is the compressor gets a nice full +12v switched by a 30a relay. That should hold forever, and if it doesn't I can easily replace the relay.
Simple, clean, and hidden away.
Fortunately there's a solution: Yes I could hand wire in a DPDT relay at the head unit, but I didn't want to do that and have a relay hanging off the side. So although that relay is too weak to handle a 3a inductive load (checked with the amp meter, it's 3a on the dot) I went with a better idea.
What I did was take a nice 30a automotive relay, SPST and wire it in under the drain pan. The wiring was as follows:
Wire from the head unit goes to one side of the relay coil, the other side of the relay coil goes to the freeze sensor. The other wire from the freeze sensor then goes to ground on the driver's side fender through the grommet. This means that the relay in the head unit now only has to switch 150ma or so instead of 3a of inductive power (which will spark/arc when opened so it's a mess).
The wire going to the compressor goes to one of the SPST contacts. The other side goes to a 12 gauge wire which goes to a 5a fuse, which goes to B+. Problem is there are not a lot of places for B+ to tap into however there is one that is always on, 12v, and has a 20a fuse on it. And it's easily accessible.
Yes, I am talking about the fan overtemp switch on the front of the intake manifold. I built a wire that plugs into the manifold switch, then goes to the +12 line via a short plug with an insulated connector, then a long wire that goes to the fuse, then the relay's other SPST contact.
Result is the compressor gets a nice full +12v switched by a 30a relay. That should hold forever, and if it doesn't I can easily replace the relay.
Simple, clean, and hidden away.
06-01-2018, 10:01 PM
#25
Rennlist Member
Thread Starter
Technically I could have placed the relay right at the point where the wire goes down to the compressor from the harness, and powered it off the same line from the fan bypass switch. Might do that down the road, although the relay would have more heat to deal with, it wouldn't be powering the unit through those really small wires.
It works, I'm happy.
06-01-2018, 10:51 PM
#26
Rennlist Member
Thread Starter
Come to think of it, if I really wanted to do this for the win I would put the relay in the engine compartment, and have it be a DPST relay with one side connected to run the compressor and the other side connected to bypass the over temp switch. That way when the AC is turned on the front fan *always* comes on at slow speed (through the big resistor) and goes to high speed when the dryer temp goes too high. More airflow over the condenser means less work for the compressor and a happier system. Since the relay will work in parallel with the over temp switch, it will still come on if the plenum temp gets too high with the car on or off.
Hm.....Might just order a 30a DPST relay and try this.
Hm.....Might just order a 30a DPST relay and try this.
06-02-2018, 09:03 AM
#27
Well Chris, it sounds like you worked out a solution.
Here is another approach in case other's have board reed relay issue:
Better Relay for AC Controller Board.... i thought there were a few threads around from years back, here is one: Better aircon clutch relay
There maybe a few other relays you can use if you search around, the one in the article is available from DigiKey here: DSP2A-DC12V
Short story on how I remembered the relay issue:
Years back when we were rebuilding the 1980-1989 compressor we sold a compressor to a client.
Client takes his shark to a dealership in Manhattan. Dealer installs our compressor and a week later the customer is back there
because the clutch would not engage. He calls us in a foul mood cursing cussing and tells us the Dealer had to put a new factory
compressor on his shark because ours failed. He returns the compressor, we test the clutch, it works fine, we refund him.
A month later he calls back apologizing because the factory replacement compressor was failing and the Dealer finally determined
it was the relay on the controller board. I thanked the customer for stepping up to the plate... a good chap.
Here is another approach in case other's have board reed relay issue:
Better Relay for AC Controller Board.... i thought there were a few threads around from years back, here is one: Better aircon clutch relay
There maybe a few other relays you can use if you search around, the one in the article is available from DigiKey here: DSP2A-DC12V
Short story on how I remembered the relay issue:
Years back when we were rebuilding the 1980-1989 compressor we sold a compressor to a client.
Client takes his shark to a dealership in Manhattan. Dealer installs our compressor and a week later the customer is back there
because the clutch would not engage. He calls us in a foul mood cursing cussing and tells us the Dealer had to put a new factory
compressor on his shark because ours failed. He returns the compressor, we test the clutch, it works fine, we refund him.
A month later he calls back apologizing because the factory replacement compressor was failing and the Dealer finally determined
it was the relay on the controller board. I thanked the customer for stepping up to the plate... a good chap.
06-05-2018, 10:05 PM
#28
Rennlist Member
Thread Starter
Indeed. It seems to be working like a charm; I'll do a write-up and take some pictures this weekend. I think I will run a second 12g wire back to the relay to allow it to bypass the temp switch and run the fan at slow speed any time the compressor is on; the more air I have going over the condenser the lower the pressures and temperatures. With an SPST relay, the only issue will be if the engine gets hot enough to trip the high temp switch on the plenum the compressor clutch will turn on along with the front fan. Annoying, but since that should only happen for a few minutes I think the clutch can handle it.
Will report back on how it works.
Will report back on how it works.
06-08-2018, 08:00 PM
#30
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Thread Starter
Nope, factory stock. But it seems to work fine, the fan comes on when the car is at idle and it's over 85 or so outside, I'm happy. Will wire up the fan to run at slow speed after I get back from Belmont; we're driving up and dad rented a Panamera V6. Same horsepower as the 928S, but it's all in the 6000RPM range as it has about 100Nm less torque.
Might get better mileage.
Might get better mileage.