A/C setback

[oscar]

I hear you Pat, and I will give it ago eventually but I also reckon your system is working better than mine for two reasons. 

Firstly, my 34 year old compressor hasn't been properly serviced/rebuilt like yours. 

Secondly, there's a few pointers to make me think there might be too much gas in it and from the above quote in my previous, I might need an aux fan.  Since HR12 is isobutane and propane, I reckon it's characteristics with plain propane would be close.  Though I don't want to go searching the datasheets to prove a point when I could be wrong.  So although more expensive, I thought I should be getting close to what you get. 

Pat, can I ask you, with propane, do you get bubbling or foaming in the sight glass of the drier?

Thanks koan, didn't know about the switches.  Because of the 90+ temp on idle with a/c on and from the quote I get the impression a fan is in order.  The one ebay I've seen is from a 350sel but I have a donor from the turd 280.  I'll be back sooner or later with wiring questions for you guys.

[Big_Richard]

Either way - its not going to happen, (freezing of the evapourator), theres either an anti icing switch, or the thermostat is calibrated, to, at full cold position cut out the compressor when it reaches ALMOST zero degrees. If the compressor continues to run when the coil is at zero, then yes, the condensate would freeze, but it dosent. It cuts out, just slightly abouve zero, with the higher threshold being about 7 degrees before it kicks in again.

[Big_Richard]

I hear you Pat, and I will give it ago eventually but I also reckon your system is working better than mine for two reasons. 

Firstly, my 34 year old compressor hasn't been properly serviced/rebuilt like yours. 

Secondly, there's a few pointers to make me think there might be too much gas in it and from the above quote in my previous, I might need an aux fan.  Since HR12 is isobutane and propane, I reckon it's characteristics with plain propane would be close.  Though I don't want to go searching the datasheets to prove a point when I could be wrong.  So although more expensive, I thought I should be getting close to what you get. 

Pat, can I ask you, with propane, do you get bubbling or foaming in the sight glass of the drier?

Thanks koan, didn't know about the switches.  Because of the 90+ temp on idle with a/c on and from the quote I get the impression a fan is in order.  The one ebay I've seen is from a 350sel but I have a donor from the turd 280.  I'll be back sooner or later with wiring questions for you guys.

Some arse clown has blanket sprayed the area with black paint, my sight glass is useless.

Go fetch some data;

Ambient internal air temperature, ambient air temperature going into the evapourator, vent temperature, condensor input temperature(refrigerant), condensor output temperature(refrigerant), ambient external air temperature. Combined with the running pressures - this will give some indication as to how the system is running.

[Big_Richard]

Just another thought - with your 14c vent temperature, is that in reciculate mode, IE colder than the line @ 3/4 mark on the dial.

It may also be somethign stupid like the recirculate flap being stuffed, make sure it is sucking the air in, from inside the car, and not outside when your getting your temp readings.

[oscar]

Pat,
Forgot to bring the gauges with me to work today.  I got a few temps, but I'll get my gauges before I do a post with full readings taken all atonce under the same conditions - BTW, refrigerant temps, do I just contact the thermocouple sensor to the enty and exit points of the condensor??



Anyway, I've got my mind set on attaching an auxillary fan.  I pulled the one off turd 280 this morning and gave it a clean.  Attached it to the battery and geez that thing is deadly.  No binding, spins freely and really pushes some air.

What I'd like to do is have the fan switch on whenever the compressor is operating as per the hychill recommendation.  Not only that, but on a warm day, with a/c on and at idle, the coolant temp creeps up too much for my liking.

So, I need power to the fan and a relay to run off the a/c clutch.  What kind of relay do I need?  Where should I grab power from?  What about a fuse?  After comparing to the other cars, there was definitley no fan on the 350 previously, so the whole circuit is new and of course differs in operation to the standard setup, but I'm in the dark as to what to get and how to set this up.  Any ideas?

[Brian Crump]

If all else fails Oscar, wire it direct to the battery with an inline fuse holder and a switch on the fascia so you can turn on the aux fan whenever you turn on the aircon.. I must be a control freak - the more switches I can control the better I feel.
Regards,
BC

[oscar]

Ok, some measurement albeit with aux fan installed.

Recirc flap and heater valve works, no probs.

Ambient internal air temperature= 26.5
ambient air temperature going into the evapourator= 29.1
vent temperature=  6.6 - 13 when cycling at idle every approx 20secs,
                                       not recirculating and 1st fan speed
                       =  11 @ max (fan set to DEF and a/c switch set to recirculating).
condensor input temperature(refrigerant)= 44,
condensor output temperature(refrigerant)= 35
ambient external air temperature= 27.6
Combined with the running pressures -
     Low side on 20psi when compressor is running, 40psi when cycled off, rests at 30psi
     High side on 115psi, variance negligible.

It's going to be good test on a hot day.  Revving the engine to 2000rpm reduced the centre vent to 7deg when at max settings.  Revving at 1st fan speed and no recirc got temp to about 6deg before compressor cycled again.

Comments??

Now the aux fan.  No dash altering non original switches inside BC.  I used a relay as pictured below (not even a bosch unit ).  Soldered a wire to the positive lead going to the compressor clutch back to the switch connection on the relay.  Earth wire to the same spot to where the clutch is earthed on the radiator sill.  Earthed fan to a condenser support bracket on front sill.  Active from fan back to relay and power from number 2 fuse to relay.

Would've like to hide the wires a bit more and the relay.  I was just a bit anxious, short of cable ties and pressed for time.  It'll be no bother to reroute the wires but something tells me that if it works well as the weather warms, I'll probably leave it out of laziness.  I'm pleased to say though that the galring red wire isn't visible through the grill,  phew.

[Big_Richard]

Based on your figures, I'm not too certain what your whinging about. It seems to be performing to a satisfactory level considering the refrigerant your using. I'm assuming you did evacuate the system correctly before charging it?

It's not R12 and never will be, regardless of all the marketing hype behind it.

PS, the thermostat should be able to be calibrated to adjust the max cold low point cutout, if your not happy with it cutting out at 6 degrees celcius. Mine is calibrated to cut out at 2, and cut back in at 7.

[oscar]

Didn't evacuate.  Haven't got a sucker.  On the bright side though, the system was inadvertently flushed in a way by wasting so much gas during my previous fill attempts whilst it leaked.  But evacuating would help.  I was just trying to achieve similar figures to you ie the 1deg centre vent.  Plus the first day I had it going was a hot one and I wasn't sure the system was up to scratch.

Where's teh thermostat BTW?  how do I adjust it?  Might tackle that next.

Also found out the alternator doesn't charge too well at idle with a/c and aux fan on.  multimeter showing 11.9v which goes to just over 12 at 2000rpm.  Got an external voltage reg and I reckon an upgrade will be on the cards next.

[koan]

Those figures look pretty good to me oscar, apart from the range of the outlet air temp. 6.6 to 13 C, mine stays stable at 8 C as the compressor cycles (apart from the 1 C I got one time).

Could be mine is a bit warm at 8 C, I do have a leak from the compressor and I might have lost refrigerant as well as oil.

Maybe the thermostat does need adjusting, I have a procedure for that. The thermostat is the A/C knob.

When you put the expansion valve in did you attach it firmly to its mounting place.

The very hot delivery hose still suggests overcharge but probably not a problem.

koan

[oscar]

If you guys are happy, the I'm happy.  36degree day predicted next thursday, that'll be the real test.

We'll look at the thermostat adjustment a little later.  The a/c panel with rotary switches etc of the yellow 280 is hanging.  I'm going to have a look at its setup before I look at the 350's.

This bit's got me wondering though -

When you put the expansion valve in did you attach it firmly to its mounting place.

I never touched the expansion valve.  All I did was unscrew the old leaking hose then screwed on the replacement.  Not easy to do, as I removed the yellow 280's hose first I thought I was going to break the expansion valve off it's mount or attachment point.  Attaching and reattaching the hose required spanner movements from 4-6o'clock.  Any higher it would seem I would damage something.  I'm thinking you guys are shaking your heads.  Clearly I've missed something here.  The expansion valves on all three cars were covered in insulation spray or wadding.  I couldn't see how to remove it nor realised I needed to.  What should I have done?  BTW, I'm very confident there's no leaks under the dash.  I observed it and smelt the area for a while before replacing the instrument cluster and lower panels.

[koan]

I never touched the expansion valve.

My mistake, I thought you replaced the expansion valve as well as the hose.

koan

[Big_Richard]

i wonder if someone has played with the placement of the thermostatic expansion vlaves bulb. It should be attatched to the suction line connection side of the evapourator, not the TXV side. The device monitors the load on the coil and regulates the amount of refrigerant allowed to boil off in it as required..

[Brian Crump]

Just out of curiousity I tested the ML - only at idle and only running for 5 minutes - got 7C on cool and 65c on hot. Bailed out then as it was too hot in the cabin....I would have expected a lower cold reading though...
I know the 450SE always feels colder than the ML so I'll test it for comparison when I get it out of storage.
Regards,
BC

[CraigS]

The 450 SE may be running with R12 and the ML with R134a. R12 was phased out because the US deemed that it caused problems with the ozone layer - which seems a bit hypocritical since they use most of the oil on the planet and won't join the Kyoto agreement - like little johnny the puppet !