Air conditioner compressor problem and query

[Bmonck]

Hello all
I have owned my 80 for 3 years trouble free. But never had the air conditioning work. Yesterday I had the gas refilled for the first time.
You may know this but when there is not enough gas in the system the a/c compressor will never turn on. So I have never had it turn on as my gas was empty.

Now the gas is full. And now whether I have the a/c turned on or off and even when I have just fans turned to off, the air conditioner compressor is turning itself on and off. When it turns on the engine automatically jumps from idle speed of 800rpm to 1200rpm. When on the open road this doesn’t matter. But I am pootling around in town or slowly along a track this obviously speeds the car up. So now relaxed driving becomes stressful as I have to “cover” the brake more often.

Anyway it shouldn’t be turning itself on when not being used I believe.
Anyone had a fully functioning a/c for years and can confirms if this is normal.
Anyone had this problem ?
Anyone any ideas as to how to control the a/c compressor?


Many thanks for all ideas.
Cheers.

 

[StarCruiser]

Sounds like it’s cycling on pressure and might have a fused AC relay or another part of the Control circuit that is shorted or bypassed somehow. First port of call would be to check the AC relay for welded contacts. As for it raising the idle too much, this is done via the idle up vacuum servo in the injection pump. I’ve not checked this but maybe there’s some adjustment on there that’s been set wrong.

As you’ve had it recharged I’m presuming the AC is now working correctly apart from this? The fans in the off position should stop the AC so something isn’t correct. Keep your fans running until you find the fault otherwise your AC evaporator could ice up and get plugged.

The idle up should just compensate for the additional load of the compressor and just lift the rpm by 100 or so max in the process.

 

[Towpack]

The AC idle up speed is indeed controlled by an adjustable, vacuum operated servo on the side of the IP, just like the power steering idle up mechanism.
Mine raises from 600 to around 800-850 rpm. I think the standard idle speed for an auto is higher than a manual but an idle up of 1200 is too high, as you have found, but is easily adjusted.
With my AC the, the blower must be switched to any one of the three speeds for the system to work. Hitting the ‘auto’ button gives control of the fan speed to the AC system.

 

[Bmonck]

StarCruiser and Towpack thanks for comments. I have adjusted the idle up for the A/c so now just adds 100rpm. So 800 to 900. Much better.

Now just need to find out why it is turning itself on and off independent of what positions the a/c button and fan buttons are in.

I guess I could also just pull the a/c fuse next to steering wheel as a fall back?

 

[StarCruiser]

Have a look at the relay. I’ll try and find where it is. In the meantime see if it drops out by pulling the 10A fuse marked ‘gauge’ then refit the fuse. Also see if it drops out by pulling the 10A ‘AC’ fuse and refit and report back on those two.

 

[StarCruiser]

On the later model a lot of the AC relays etc are located behind the glove box.

 

[clivehorridge]

On mine I have an A/C push-button switch. I dont have the climate control push-button panel so it may be different.

Anyway, the A/C clutch isn’t energized at all when the button is off, but when on, it cycles in and out as you’d expect. So I’m guessing the relay (Rich @StarCruiser) is talking about is activated by that switch (or equivalent on the climate control panel) if you have a separate switch that is...

 

[Bmonck]

Gents again many thanks

Yes I have an a/c push button. And an automatic button. But compressors kicks in and out whatever position the a/s switch is in or the auto button.
I will check with fuses, probably tmrw now.
Then finally will wrestle to find relay.
Cheers again

 

[Dave2000]

Have your gas pressures rechecked the compressor will cycle on/off if system pressure is too high or low, check your viscous fan coupling is working properly, insufficient air being pulled through the condenser will have the compressor in a tizzy.

Regards

Dave

 

[Towpack]

The problem is that the AC is still operating when it's turned off so I don't think refrigerant pressure or airflow etc have any bearing. It must be an issue on the control/operation side, maybe either the AC amplifier unit or an AC relay but not the magnetic clutch relay.

 

[StarCruiser]

The problem is that the AC is still operating when it's turned off so I don't think refrigerant pressure or airflow etc have any bearing. It must be an issue on the control/operation side, maybe either the AC amplifier unit or an AC relay but not the magnetic clutch relay.

There’s quite a few to chose from. Hence the test to see which fuse stops the problem, or more useful, which one doesn't.

 

[Dave2000]

Completely misread the OP ignore me.

Nothing to add to the above, and going back to bed.


Regards

Dave

 

[Dave]

Have you got a fridge?

 

[StarCruiser]

Have you got a fridge?

Good call Dave, Didn’t think of that.
I suppose the Fridge overrides everything causing the compressor to run when the AC is off and the fan is off. I haven’t got one so don’t know for sure but that certainly would make sense. Perhaps somebody with one could confirm operation. Of course it does all depend on whether Bmonck has one.…

 

[Bmonck]

Gents that’s a smart question. I assume you mean the fridge in th centre arm rest. And Yes I do. Normally is turned off but let me double check that wasn’t on by mistake and triggering the a/c compressor. (Big fridge /freezer in the back is completely independent of course ). Back shortly. ......

 

[StarCruiser]

Some have rear AC too though I’m not sure if you could get Fridge and rear AC.

 

[Bmonck]

Aha. Never noticed a/c in the back but don’t have seats in the back so wouldn’t have. So will check that too thanks

 

[chapel gate]

Aha. Never noticed a/c in the back but don’t have seats in the back so wouldn’t have. So will check that too thanks

You would notice! Theres a large clear tube going up the side to vents on the ceiling.

 

[Dave2000]

Gents that’s a smart question. I assume you mean the fridge in th centre arm rest. And Yes I do. Normally is turned off but let me double check that wasn’t on by mistake and triggering the a/c compressor. (Big fridge /freezer in the back is completely independent of course ). Back shortly. ......

They are a bloody nuisance, strip it out very carefully, pack well and post to me, I have a place to put it for the rest of its life, and promise it will never bother you again.

Regards

Dave

 

[Bmonck]

Gents
So this is the update
- no rear a/c, sorry Dave
- when I turn on the centre console cooler it does seem to lead to compressor cycling on and off, but weirdly there is no cold air. So I don’t know if they are connected to the a/c cold air circuit or not. Still when this centre console is turned off the compressor cycling stops. So that’s a partial result.
- when I remove the a/c fuse (in panel next to steering wheel) the a/c compressor keeps going. But when I remove the gauge fuse it stops. So now I know which fuse too. Thanks Star Cruiser.
So will now monitor for a few days before diving in to the relay world, where I will be really out of my depth.
Thanks again for all your ideas and help. I have learned some good stuff and fixed the idle up issue.