Air con intermittent

Ok done a search, nothing found so here goes......
300TDI auto
Engine on, in park, turn on fan to 1 or above, turn on air con, idle speed increases, cooling fans start, compressor engages, cold air through vents,
After a few seconds compressor disengages, then reengages, and so it goes on, all seems OK, cold air continues.....
Drive off, and in a very short time cold air disappears. It's as if it will only work when stationary
If you have been driving for a while with air con off, and turn it on while driving, no cold air......
Weird, but has to be something really basic, as when stationary it works perfectly, any ideas please????

Thanks all

it sounds like a short in the wiring .check plugs and fuse and also relays

One thing I do know is that the aircon turns off if the engine overheats. You shouldn't be overheating that quickly, but maybe you've got a dodgy temp sensor.

Other posters suggestion sounds likely as well.

Cheers!

Thanks guys, I'll have a look at the weekend

And make sure the belt is tight

Belt is fine, good call though

Just had a look at Rave. There are various switches that will switch off the aircon. Extract below (I assume you've got EDC as it's an auto), but the main ones are the ones monitoring the refrigerant pressure (too low or high will switch off aircon), and the evaporator temp switch - that should stop the aircon if the system is icing up. I suspect your problem is either one of these switches is faulty or your system pressure is incorrect. In all cases you would need an aircon specialist to fully diagnose, unless you ran some test wires into the cabin!

Good Luck
Graham Carter


Compressor Control (300Tdi with EDC) With the Ignition Switch (X134) in position II, battery voltage is applied to the Ignition Load Relay (K127). The relay is energised, applying battery voltage to the Compressor Clutch Relay (K108). When the Front Fan Speed Switch (X247) is turned to positions I, II, III, or IV and the Front A/C Switch (X225) is turned on, ground is provided to terminal 44 of the Engine Control Module (ECM) (Z132) through the closed contacts of the A/C Dual Pressure Switch (X102) and the Front A/C Evaporator Temperature Switch (X101). The signal informs the ECM that compressor operation has been requested. The ECM then provides ground to the coil of the Compressor Clutch Relay (K108). The relay is energised, applying battery voltage to the Compressor Clutch (K107). Compressor Clutch operation is now controlled by the status of the A/C Dual Pressure Switch (X102) and the Front A/C Evaporator Temperature Switch (X101). The Front A/C Evaporator Temperature Switch (X101) is fitted in the airflow out of the front evaporator to sense the temperature of the exterior fins. Should ice begin to form due to low temperature, the switch will open. The A/C Dual Pressure Switch (X102) monitors refrigerant pressure in the high pressure line. Should pressure become too high or too low, the switch will open. When one or both of these switches open, the ground supply to terminal 44 of the ECM will be interrupted. This signal informs the ECM that compressor operation should be turned off. The ECM removes the ground supply to the coil of the Compressor Clutch Relay (K108). The relay then de–energises, removing battery voltage from the Compressor Clutch (K107), thereby disengaging the Compressor

Low gas pressure will cause this to happen.
You can get aerosol top up cans from e bay i have used a couple before work a treat and about 13 quid from memory.


Lynall


Lynall

lynall said:

Low gas pressure will cause this to happen.
You can get aerosol top up cans from e bay i have used a couple before work a treat and about 13 quid from memory.

Click to expand...

:5biagree::5biagree::5biagree:

What Lynall said. (about £17 nowadays)

Wonderful feedback guys, thanks soo much!!! Looks like a can of top up as the way to go as a first try, yippee something to give a go, happy days
DO I need to buy the £40 version with the hose and meter so I dont over gas? Or is there another version I'm not finding?
http://cgi.ebay.co.uk/WEBSITEINBOUN...ltDomain_3&hash=item5190f06f8f#ht_1106wt_1141

Tallbiker said:

Wonderful feedback guys, thanks soo much!!! Looks like a can of top up as the way to go as a first try, yippee something to give a go, happy days
DO I need to buy the £40 version with the hose and meter so I dont over gas? Or is there another version I'm not finding?
WEBSITEINBOUND_AIRCON_TOPUP_CAN | eBay UK

Click to expand...

Get something with a gauge and understand how it works/what it means. You want to see what pressure it is at after it's been switched off and sitting. If it's less than the vapor pressure of R134a, it means you have NO liquid refrigerant in there. Here's a calculator.

If you have less that x psig at whatever temperature it is outside according to that calculator or a chart that might be on the can, you'll be needing about 650 grams of refrigerant (the whole system is 700g). If you have rear aircon it's a bit more.