Overheating when air con is on

bigfella_V5

MG ZS 180 - V6
Feb 25, 2007
274
0
I think there may be more than one issue here.

When at speed the air con works perfectly, blasts lovely cold air.

But sometimes when at idle I get a vibration though the throttle peddle and hear some sort of air lock or noise clearing. Very difficult to explain the noise but it changes pitch and disappears.

Also at idle a couple of times the engine temp has risen to 100c, I didn't like the look of this so turned the air con off and turned the heating right up and the temp returned to normal. I do not see any signs of the fan(s) kicking in.

Now with the air con off, the and the car running at idle I have left it for 10-15mins in the hot weather and the engine temp hasn't moved!

Any ideas?
 

JamesF

Guest
The reason why it cools down when the air con is off is cos its taking hot air from the engine bay. Thats a trick I had to do on my 306 when the thermostat was bust. If its a problem with the thermostat, idling wont have any effect on overheating.
When the engine temp rose to 100°c, was that when you were driving hard? Has it been especially warm down there recently? Its been pretty warm up here. Nothing major, but 10°c or so in ambient temperatures would have an effect on the intake temperatures. Common sense really. So if its normally at 90°c and when you hoon it it goes to 96°c, if the intake temp was 94°c, it would go to 100°c when you were driving spiritedly. Making you think "Balls! 100°c!!!", when in reality, it might only be a few degrees over normal operating temperature.

Im not overly sure how easy to access things are in a VAG engine bay (even though Im driving a mk4 Golf at the moment.

Try finding the connector for the thermostat / fans, (Haynes?) short circuiting the connects with wire (in effect, making it think it was on). Actually, short circuiting is a bad choice of words. DONT SHORT CIRCUIT ANYTHING!!!

*complete* the circuit!

Thats what I meant to say. Again, this is a shot in the dark but maybe try VAGCom see if its throwing any codes.

No idea if this is actually helpful, or even true!!! Just thought Id throw in a little bit of advice mate.

Hope you get it fixed.

James

PS - theres lots more members on http://uk-mkivs.net so Id have a gander over there if I was you ;)
 
Last edited by a moderator:

bigfella_V5

MG ZS 180 - V6
Feb 25, 2007
274
0
Cheers James, I will join up now.

As for the temp issue, it was rising - I just did something about it when it reached just over 100. I was just creeping along in traffic. This is fine with the aircon off.

When I saw it getting high as a precaution I turned up the heating and turned the aircon off to reduce engine temperature.

I have had a look with my VagCom and there are no fault codes that would be anything to do with the problem I'm having. Just a lambda probe fault.
 

JamesF

Guest
Hmm... Weird. It sounds to be a thermostat problem or something. But like you said, its throwing any codes. Maybe the fans are loose on the motor shaft or something! :D

Hope you get it sorted mate
 

dchbrown

Full Member
Feb 17, 2006
115
0
South Coast
not wanting to hi-jack the thread here but its kinda related so....

Is it normal for the fan to kick in quite early on the V5 engine?
 

GrayT

I'm Old
Jul 7, 2004
812
5
London
In my experience it does compared to other cars BUT you need to read the link in post 9 of this 'sister' thread on the MKIV's forum. If the fan is always on and off (pulsing) then you may have the problem they refer to (assuming that you have checked your coolant level is OK as a first stop). It is not unusual for the fan to run on my engine for a number of minutes after I have stopped driving and switched off ignition after a stop/start commute in hot weather.
 

JamesF

Guest
Now Im definitely getting a Toledo V5 if it can make my tea!!! Plus I dont need to keep this string of manky women around me who can cook!!!
 

bigfella_V5

MG ZS 180 - V6
Feb 25, 2007
274
0
Haha nice one! Glad my drive is all dual carriageway from 2 mins of starting her I'm on the dual carriageway so cooling shouldn't be a problem. I will have to get it fixed next month.
 

Stubill

Swine Bird !
Aug 13, 2002
323
0
The New Forest
Visit site
Cooling fans should always kick in before 100 deg !
Basically the engine temp should never budge off 90 regardless.

Check the fuses on top of the battery (under the plastic flap) - one of the 30A is for the engine cooling fans. Common fault on the V5.

Cheers.

EDIT : Even if no signs of it being blown - check the fuse housing for any damage that may cause an intermittant connection of the fuse. Hope that helps.
 
Last edited:

bigfella_V5

MG ZS 180 - V6
Feb 25, 2007
274
0
Cooling fans should always kick in before 100 deg !
Basically the engine temp should never budge off 90 regardless.

Check the fuses on top of the battery (under the plastic flap) - one of the 30A is for the engine cooling fans. Common fault on the V5.

Cheers.

EDIT : Even if no signs of it being blown - check the fuse housing for any damage that may cause an intermittant connection of the fuse. Hope that helps.

Yep, fuses are all OK, no damage at all to the fuse panel on top of the battery. Its really strange - I need to get under the car to gain access to the fan connector so I can run a live down to them and see if the fans come on.
 

bigfella_V5

MG ZS 180 - V6
Feb 25, 2007
274
0
Right had the car on axel stands.

I ran a live down to the fans and they only work on full power. Upon testing with a multimeter it appears that I get high resistance on the red/white and brown so the fans are faulty.

I then bridged the connections on the three pin plug and left the multimeter on the fan connector (car end) and measured the voltage and there was nothing. I could hear a box where I think the fan wires came from clicking. As if a relay is opening and closing but strangely there was now power going to the fans as the multimeter showed.

Providing a live is getting down to the fan controller, which I'm quite certain there is as I tested the fuses on top of the batter with a multimeter the wiring should be OK.

From these tests I believe I more than likely have a faulty fan control box and both fans are faulty. What do you think?

Thanks,

Matt
 

dchbrown

Full Member
Feb 17, 2006
115
0
South Coast
From these tests I believe I more than likely have a faulty fan control box and both fans are faulty.

Have you sorted out this problem yet bigfella_V5?

Ive just realised that my V5 is doing the Pulsing thing and it nearly overheated in traffic with the aircon on so its obviously the same problem.

What have you replaced to fix it? And if you dont mind me asking how much was it?

David
 

bigfella_V5

MG ZS 180 - V6
Feb 25, 2007
274
0
Yep, all sorted this weekend!

Right, replaced the fan control unit - £20 from eBay. Was a gamble as it could have also been faulty.

As yours is worked (fans actually pulsing instead of not working at all) it shows you don't need this replaced.

As well as that I purchased a PWM controller from www.nime.co.uk - might seem expensive but its a clever piece of kit that saves replacing the fans.

Was tricking to solder to the beefy wires as I couldn't get it hot enough - I had to use the blowtorch function of my solder iron to heat the wire up, caused the insulation to melt a little but nothing some tape can't solve.

Drove to Twickenham yesterday with the aircon on (and sat in traffic) and it was absolutely fine!

Only thing I would say is that I haven't been able to test the highspeed function of the fans as the car has not got hot enough - I'm sure this will be fine as the low speed works fine.

Until you have fixed the problem DO NOT USE THE AIRCON!
 

dchbrown

Full Member
Feb 17, 2006
115
0
South Coast
Well ive been quoted £111 & £116 + VAT for the fans alone so that controller would be a much cheaper option!!!

Did you lose both your fans then?

I need to check on mine a bit more because i had a bit of an overheating moment and havent dared use the aircon since so i need to investigate whether ive still got any fans at all or not!!
 
Nimbus hosting - Based solely in the UK.