Heating system - Problem

Metallo · Nov 30th, 2002, 15:37

Hi,

I've got a 940 SW 2.0 Turbo - Petrol - 1997 and I am having a strange problem with the heating system.
I may take the car, go to the supermarket and the heating doesn't work. 15 minutes later it suddenly works but can stop again after any time. If I switch the A/C on, I have the same problem.
The fan is working properly, meaning that the air is coming out regularly.

The only signal I've got is that when I turn the ignition key from "0" to any position 1, 2 or 3 (which means engine on), I hear for 7-10 sec. a tic tic sound (similar to the one of a relay switch) coming from the back of the dashboard, difficult to say where from exactly, could be the back of the ventilators or back of the radio.
If I turn the ignition key to "0" it obviously stops but if I turn it on again to any position the tic tic sound starts again for 10 sec., then it stops anyway and the heating doesn't work.

I don't know if this can help to detect the problem, but really this is the only anomaly I have noticed.

Hope you can help.

Nov 30th, 2002, 17:57

Hi Alex,

Have you been working on the cooling system recently?? Like changed the anti freeze or something like that? the easiest way to check this is to lift the front as high as possible so that the car rests only on it's rear wheels, then proceed to top up the system. Leave the cap off and start the engine and watch for the bubbles to appear out the expansion tank, once it has settled level, then top up as normal and refit the cap.

Another possibility, thinking about it, could also be a sticking thermostat and may need checked and replaced. The Ticking sound that you describe sound like the stepper motors on the heating system adjusting themselves, happens all the time on mine, although I don't have a problem with heating:-)

Hope this helps

Regards
Dave M

sheerwater · Nov 30th, 2002, 23:23

Hi,
On my car the valves on the heating flaps are vacuum controlled from the engine. By any chance has the vacuum tube....small about quarter inch diameter....been squashed, split, come adrift? Secondly is the hot water valve working? Regards the toping up Dave mentions the system is not one that regularly needs to be bled like other modern cars but there could be exceptions. Cheers Nige

Nov 30th, 2002, 15:37	#1
Metallo Member Last Online: Apr 21st, 2024 23:43 Join Date: Nov 2001 Location: Fredericton	Heating system - Problem Hi, I've got a 940 SW 2.0 Turbo - Petrol - 1997 and I am having a strange problem with the heating system. I may take the car, go to the supermarket and the heating doesn't work. 15 minutes later it suddenly works but can stop again after any time. If I switch the A/C on, I have the same problem. The fan is working properly, meaning that the air is coming out regularly. The only signal I've got is that when I turn the ignition key from "0" to any position 1, 2 or 3 (which means engine on), I hear for 7-10 sec. a tic tic sound (similar to the one of a relay switch) coming from the back of the dashboard, difficult to say where from exactly, could be the back of the ventilators or back of the radio. If I turn the ignition key to "0" it obviously stops but if I turn it on again to any position the tic tic sound starts again for 10 sec., then it stops anyway and the heating doesn't work. I don't know if this can help to detect the problem, but really this is the only anomaly I have noticed. Hope you can help. __________________ 940 Polar 2.0L Turbo SW - B200FT - 1997 XC 70 2.5L SW - 2006

Nov 30th, 2002, 17:57	#2
Dave M Guest Location:	RE: Heating system - Problem Hi Alex, Have you been working on the cooling system recently?? Like changed the anti freeze or something like that? the easiest way to check this is to lift the front as high as possible so that the car rests only on it's rear wheels, then proceed to top up the system. Leave the cap off and start the engine and watch for the bubbles to appear out the expansion tank, once it has settled level, then top up as normal and refit the cap. Another possibility, thinking about it, could also be a sticking thermostat and may need checked and replaced. The Ticking sound that you describe sound like the stepper motors on the heating system adjusting themselves, happens all the time on mine, although I don't have a problem with heating:-) Hope this helps Regards Dave M

Nov 30th, 2002, 23:23	#3
sheerwater Master Member Last Online: Feb 24th, 2019 17:59 Join Date: Dec 2001 Location: Northampton	RE: Heating system - Problem Hi, On my car the valves on the heating flaps are vacuum controlled from the engine. By any chance has the vacuum tube....small about quarter inch diameter....been squashed, split, come adrift? Secondly is the hot water valve working? Regards the toping up Dave mentions the system is not one that regularly needs to be bled like other modern cars but there could be exceptions. Cheers Nige

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