Nina's 1981 244 GL - "Billie"

jamesinc

bgpzfm142;122137 wroteIs there a heat shield for the MC?

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Besides, the slow loss of pedal pressure (up to a point - the pedal doesn't bottom out entirely) leads me to think it's the valving in the MC or something, rather than boiling the fluid. The current fluid is only a month old, and even without the heat shield we had fluid in for at least 6 months before it started getting soft. So my thoughts are that the biggest problem by far is some kind of fault in the MC. It might explain also why the brake failure block engages sometimes, if there's a valve leaking, it might be applying uneven system pressure.

sucksqueezebangblow

Proportioning valve? You should swap it out to an adjustable burn out one anyway.

alphax

jamesinc;122139 wrote
bgpzfm142;122137 wroteIs there a heat shield for the MC?
Scroll up

Besides, the slow loss of pedal pressure (up to a point - the pedal doesn't bottom out entirely) leads me to think it's the valving in the MC or something, rather than boiling the fluid. The current fluid is only a month old, and even without the heat shield we had fluid in for at least 6 months before it started getting soft. So my thoughts are that the biggest problem by far is some kind of fault in the MC. It might explain also why the brake failure block engages sometimes, if there's a valve leaking, it might be applying uneven system pressure.

I've had cheap master cylinder's fail when adding new fluid. Fail = slow internal leak and loss of pedal pressure. When I still ran a Volvo master, I found the ATE oem spec master cylinder to be similarly priced to a Chinese Protex unit from ATAP and much better quality.

jamesinc

Yes, I discovered last night Ate branded masters are like $20

jamesinc

w o r k i n g

a i r

c o n d i t i o n i n g

Man that was more effort than I would have liked.

Slowbrick

Did you add the AC in?

jamesinc

Slowbrick;122623 wroteDid you add the AC in?

It did have (non-functional) AC originally, but when we put the B230 in I added a native R134a compressor. I replaced all the o-rings and dryer. I need to relay the low speed of the efan to the compressor clutch, but I am just waiting on a relay to arrive in the mail.

Philia_Bear

jamesinc;122625 wrote
Slowbrick;122623 wroteDid you add the AC in?
It did have (non-functional) AC originally, but when we put the B230 in I added a native R134a compressor. I replaced all the o-rings and dryer. I need to relay the low speed of the efan to the compressor clutch, but I am just waiting on a relay to arrive in the mail.

I've got like 10 of the stock p80 relays in stock

jamesinc

Philia_Bear;122629 wrote
jamesinc;122625 wrote
Slowbrick;122623 wroteDid you add the AC in?
It did have (non-functional) AC originally, but when we put the B230 in I added a native R134a compressor. I replaced all the o-rings and dryer. I need to relay the low speed of the efan to the compressor clutch, but I am just waiting on a relay to arrive in the mail.
I've got like 10 of the stock p80 relays in stock

I already have that relay pack, this is a relay on that relay. For posterity, here is how I've got everything set up (fuses not shown):

jamesinc

I had to change that wiring diagram slightly. The voltage drop across the relay was too great and the clutch wasn't engaging. So instead now the relay and clutch are in parallel.

The whole system is putting a pretty big load on the alternator, I'm going to change it out for a 100A to be safe.

I might also add a 10" pusher fan to the front of the condenser. I also need to potentially change the heater control valve as it seems to let a small amount of coolant by even when set to cold (checked cable adjustment already).

Finally, I need to seal up the many vast gaps around the radiator and intercooler to encourage better airflow. I'm going to buy some sheet aluminium for this, and a metal bending brake (I've wanted a sheet metal bender for ages, I'm half tempted to make my own, but they're very cheap on eBay)

Revised:

jamesinc

I took the car back to my AC guy this morning with the fan hooked up and we re-tested the system pressures, and it's good! Head pressure is nice and stable and the low side line is ice cold. Air in the cabin is only mild, but that's because the heater valve isn't closing properly.

I ordered one of the new-style heater valve retrofit kits. I have to say, I've built a car from a shell, but the AC in this car and in Amy really takes the cake for throwing money at something. I suppose next step is tinted windows.

Vee_Que

Wait. You trigger the fan from the pressure switch rather than the ac switch itself? Australian cars with the best ac run with the fans on at all times with the ac switched on, regardless of pump operation. To me this makes sense as truck makers do the same.

jamesinc

What are you running the fan for if you're not running the compressor?

Vee_Que

Literally switched from the wire that goes to the pressure switch, but the always on side instead of the side that cycles. Maybe I've misread your diagram.

Nope, so the e-fan ideally should come on when you press the ac Button inside the car and stay on.

jamesinc

The pressure switch wouldn't normally ever open unless there was a system fault I think.

Edit: @Vee_Que thinking about it, the 240 doesn't have a master on/off, it just has an adjustable thermostat, so I have no way of knowing that the system is on but compressor off.

Vee_Que

I thought they turned all the way past and clicked off? They would need too.

The pressure switch is the bit that cycles the compressor so it does turn on and off.

Slowbrick

Vee_Que;122982 wroteI thought they turned all the way past and clicked off? They would need too.

The pressure switch is the bit that cycles the compressor so it does turn on and off.

There are two different styles. The earlier ones used that dial switch which has a copper capillary tube. When the system gets to the right temp it closes the tube and turns the compressor off. The pressure switch iirc was on the dryer and was used to operate the fan of the head pressure rose too high.

The later system used a simple on and off switch which fired a relay. This system used two pressure switches, one behind the condenser and one on the dryer. This system was tied into the ECU which controlled how long to run the compressor based on the results from the pressure switch. This system also had the aux fan controlled by a pressure switch.

A popular modification was to have the fan to run all the time even between cycles to keep the condenser cooler which increases efficiency as it keeps it closer to ambient temps. I personally will have one 940 efan controlled by a thermostat on the low speed, one on the pressure switch on the low speed and a manual switch on the high speed which will be used for days at the track or when extra cooling is needed.

jamesinc

I'm not using a stock setup either way. The pressure sensor isn't the Volvo OE one, it will only open the circuit if there's low refrigerant pressure, or if it's crazy high. Under normal operating conditions it is always closed, so basically the fan is always running unless the cabin thermostat opens the circuit.

Vee_Que

I've not seen a switch that works quite like that to control the ac pump..

jamesinc

Vee_Que;123047 wroteI've not seen a switch that works quite like that to control the ac pump..

¯\_(ツ)_/¯

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