AC Control unit, 960.

[mjk164]

Hi all, looking for some help.
My car is a 1993 960, 2.9 auto with Air con, R134 gas, ECC unit. The gas system is fully charged but I can hear a relay clicking from the A/C unit. It is the A/C control unit (Volvo part 1365678) and it is located on the heat exchanger housing by 2 screws. To get access, remove the glove compartment and the passenger footwell panel and its tucked away in there....but just accessible to remove it. I know that's the cause of my problem as I can hear and feel the unit clicking, which in turn has an effect on the a/c cooling and the lovely slow running of a 6 cylinder engine. I understand the part number is 1365678 and is listed as no longer available. Anyone have a used part tucked away or can send me to a possible source....or a repair? I have had the unit out and cleaned up the 2 contacts inside but I suspect there is something else bad inside as it if still faulty.

[Laird Scooby]

Originally Posted by mjk164

Hi all, looking for some help.
My car is a 1993 960, 2.9 auto with Air con, R134 gas, ECC unit. The gas system is fully charged but I can hear a relay clicking from the A/C unit. It is the A/C control unit (Volvo part 1365678) and it is located on the heat exchanger housing by 2 screws. To get access, remove the glove compartment and the passenger footwell panel and its tucked away in there....but just accessible to remove it. I know that's the cause of my problem as I can hear and feel the unit clicking, which in turn has an effect on the a/c cooling and the lovely slow running of a 6 cylinder engine. I understand the part number is 1365678 and is listed as no longer available. Anyone have a used part tucked away or can send me to a possible source....or a repair? I have had the unit out and cleaned up the 2 contacts inside but I suspect there is something else bad inside as it if still faulty.

What is the system not doing Martin?

[mjk164]

Thanks for coming back Dave. I usually run the engine with the AC always on and the ECC controlling the temperature, usually set at 18c to 20c, and it works fine. You can feel the filter/accumulator (next to the engine bulkhead on the passenger side) and its cold and you can have the air coming into the car at whatever you set it at. However, after running for just a few minutes, you can hear a relay clicking i.e. switching in and out, and it starts to have an effect on the tickover, making it unstable. (It doesn't switch the AC pump clutch in and out, but the clutch does operate in its normal fashion responding to gas pressure.) But the clicking of the relay in the AC control unit does feed into the engine management system to affect the engine running. If I switch the AC off at the ECC dashboard controls, then the pump AC system goes off, no relay clicking, and the engine runs normally as you would expect. I've had the control unit out with the cover off and observed the relay clicking and out. The control unit is reported as no longer available so any help is welcome. I have used some crocus paper on the two relay contacts but that is not the fault; its somewhere in the card and associated electronic units. The card soldering looks good. Any suggestions Dave or "used but good" units?
Thanks, Garth.

[Laird Scooby]

Originally Posted by mjk164

Thanks for coming back Dave. I usually run the engine with the AC always on and the ECC controlling the temperature, usually set at 18c to 20c, and it works fine. You can feel the filter/accumulator (next to the engine bulkhead on the passenger side) and its cold and you can have the air coming into the car at whatever you set it at. However, after running for just a few minutes, you can hear a relay clicking i.e. switching in and out, and it starts to have an effect on the tickover, making it unstable. (It doesn't switch the AC pump clutch in and out, but the clutch does operate in its normal fashion responding to gas pressure.) But the clicking of the relay in the AC control unit does feed into the engine management system to affect the engine running. If I switch the AC off at the ECC dashboard controls, then the pump AC system goes off, no relay clicking, and the engine runs normally as you would expect. I've had the control unit out with the cover off and observed the relay clicking and out. The control unit is reported as no longer available so any help is welcome. I have used some crocus paper on the two relay contacts but that is not the fault; its somewhere in the card and associated electronic units. The card soldering looks good. Any suggestions Dave or "used but good" units?
Thanks, Garth.

It sounds like it's running as it should Martin, try turning the temperature up a bit to see if it takes longer to first start the relay/compressor clutch cycling and also if it makes the duration of each cycle a bit longer.
At this time of year, holding it to 18-20C (18 is also minimum which will force the compressor permanently on) even when just warming up is going to be tricky. Might be worth blowing or vacuuming the interior light in the middle of the roof as that's where the cabin temp sensor is for the ECC.

Also try cleaning out the AICV to help maintain a steady idle when the compressor kicks in.

[mjk164]

Noted Dave and thank you. I had forgotten about the cabin sensor; I'll do that and the AICV.
Get back to you later.

[Laird Scooby]

Originally Posted by mjk164

Noted Dave and thank you. I had forgotten about the cabin sensor; I'll do that and the AICV.
Get back to you later.

Forgot to say Martin, it might also be slightly low on gas - not low enough to stop the A/C working but low enough to keep it cycling on and off more than it should. Might also be worth putting the ECC into diagnostics mode and checking to see if there are any fault codes shown :

https://www.volvoclub.org.uk/faq/Hea...iagnosticCodes

Probably won't show anything but worth a try.

[mjk164]

Thanks Dave. I have my own R134 gas and charging/recovery system and I always keep it full. Before coming on with my original request for help, I checked the charge and it was good. The 960 system takes 0.9 Kgs for a full charge and I find that it looses about 0.1 kgs a year. And I will check the OBD's to see if there is anything. Lot of rain this morning so have delayed doing those other checks, but I will and report.
Thanks.

[mjk164]

Well Dave, when removing the cabin sensor just now, apart from the spider living in there, the sensor was well covered with dust and everything else. So cleaned it up and replaced and the system is much better, still relay clicking slightly but that might stabilize with use; but certainly an improvement. Nothing on the ECC fault OBD system.
Thanks.

[Laird Scooby]

Originally Posted by mjk164

Well Dave, when removing the cabin sensor just now, apart from the spider living in there, the sensor was well covered with dust and everything else. So cleaned it up and replaced and the system is much better, still relay clicking slightly but that might stabilize with use; but certainly an improvement. Nothing on the ECC fault OBD system.
Thanks.

That's good news Martin (apart from the now homeless spider ) and ties in with my theories. Given that it's still not that warm at the moment, the gas might still be a smidge low in terms of pressure, should improve once the weather warms a bit more and should also help to dampen the on/off nature of the compressor.

If you feel like removing the glovebox, there should be a cover over the evaporator that also serves as a vacuum reservoir which looks like 3 tennis balls in a sock. Behind the evaporator (in terms of air flow) is a filter which over time gets clogged with dust, leaves etc so it's possible that's keeping the evaporator at an artificially low temperature not letting the TXV (Thermal Expansion Valve do its job properly.



That's the cover/reservoir, if memory serves there are 6 screws holding it on.



I had to source a replacement evaporator for mine (previous owner had it removed, long story but basically incorrect diagnosis!) so that's the filter on it when it arrived. I used a piece of filter material designed for a motorbike cooling system radiator :



Those little "spiders" have a "leg" that secures the filter into the fins in the evaporator, should be possible (although fiddly) to remove them and fit a new filter or clean the old one in washing up liquid and warm water. Alternatively if you can empty the system, you can remove the evaporator. You'll need PAg oil for the compressor when you refill it though.

The other thought that's just occurred to me is you say you've added about 100g of gas yearly to the system? Did you ever vacuum it down completely? If not, it's possible the reciever/dryer (big silver canister not quite on the bulkhead) is full of moisture that's freezing when the gas hits it and causing a blockage and the compressor to go out on the high pressure switch as a result. Once it stops running, engine bay heat will defrost the reciever/dryer allowing the compressor to kick in again.
If you do recover all the gas and vac it down, i'd leave the vac pump running for a good half hour but preferably longer to boil any moisture in the system off.

[mjk164]

Thanks again Dave for a lot of info. On the a/c I always vacuum down & recover before refilling. Your pics show the filter cloth and I did all that about 2 years ago...for the second time in my ownership. (I also have my own filter cloth fitted across the round main air inlet underneath the wiper panel.
You would be surprised just how much leaves and muck that simple cloth is able to stop from getting into the system). In your first pic of the footwell, just above the yellow Volvo label, is where the a/c control unit is located and its cooling measuring fins, go into the evap space. The bunch of wires close by the label, to the right, go to the control unit. I've had all that evap system lot out about 10 years ago when renovating the leaking a/c system; there was a leak in the pipe from the pump going up to the drier; where the pipe is secured to the top of the chassis member by sponge lined clips. Its the sponge that holds water (with salt?) and eats away at the aluminum pipe. Because of the feedback system in the electronics, it may take an hour of "normal" running for it to re-set to the revised control system. Be careful with the Pag oil, its not very nice stuff. The drier is new and cheap so easy to replace when draining down.
Anyway, I think I'm about there now.... oh and the spider was re-housed!