A/C vs Radiator issues.

[Soarerpete]

hey all,
Wonder if anyone has this issue, had it or am I the lucky one.
My car runs perfect heat generally. I have aluminium radiator, sard thermostat and Davies Craig thermo fans.
But the issue is overheating whenever air conditioner is on.
Now I needed to look into this further and found overheating isn't the actual cause, this is only the aftermath.
Whenever the air conditioner is turned on, the radiator overflow will expel fluids, now obviously when it runs out of water along with the radiator, the car will overheat. Again temp is perfect through this entire process until car runs dry.
So I'm trying to understand why the pressure buildup inside the radiator is caused, and why it NEVER happens unless air con is turned on?

I am from QLD and external fresh hot air isn't the most pleasurable.

 

[whats_doing]

How is your radiator cap?

 

[pretzil]

your fans come on with AC on?

 

[steveP]

I had this exact same problem when I first got my car. I was worried it was an auto electrical problem, and it sort of was; the plug for the AC fan had come loose.

 

[NuffNuff]

do two things, change your radiator cap to a stock cap. and change your thermostat.

my radiator cap went first, then my thermostat seized up. they are the easiest and cheapest troubleshooting.

i chucked my thermostat into 80, 90, 95, 100 boiled water and it would only open slightly on all temps. currently running no thermostat and it was a quick rush job to get going for a camping trip

i found mine was overheating only with aircon on too, because the condenser gets hot i believe and puts the seized thermostat over its already crippled limit

 

[jungle]

your fans come on with AC on?

+1
Also what brand radiator is it?

 

[Soarerpete]

@whats_doing im pretty sure the cap is fine,
@NuffNuff thermostat is only a year old
I'd still think these items would show heat problems without air con as well, but even if the car gets a hiding it's still holding normal temp.
I will definitely have to check on the fans while AC is on and see

I'm still confused though with the fact it runs perfect temperature even with air con on, it's only that it starts spewing out of the overflow. Temp is still fine right up until there's low fluid levels. Only then does the needle move up????

 

[AKKO]

What type and rating of cap is it?

Also given the SARD is a 65 opening temp is the coolant even staying in the rad long enough to transfer any of the heat out?

With the fans what's there operation, with partial vs full voltage as modulated by the factory controller or do you have aftermarket with a separate sensor?

 

[trotty]

I'm
Wondering how the fans are mounted. Are they tight to the radiator to draw air through or are they able to recirculate enging bay temps? Stock shrouds have defusers to draw air through the whole core. If u only have circles u are not effectively using the rad or condenser.

 

[trotty]

I would also replace the cap or see if it's seated I've had the rubber ring dislodge and sit to the side.

 

[pretzil]

If u only have circles u are not effectively using the rad or condenser.

I just had this made for my Golpher radiator, before this I had just 2 circles, but never had any issues like what you are describing:

The fact that this only happens when the aircon is on makes me wonder if the fans are wired correctly.

 

[AKKO]

The fact that this only happens when the aircon is on makes me wonder if the fans are wired correctly.

Agreed, sounds like they might be going from hi-speed to lo-speed when they should be doing the opposite?

 

[naughtika]

thought the fans go FULL ON when the a/c is ON.. ?!?

 

[AKKO]

thought the fans go FULL ON when the a/c is ON.. ?!?

That's what they should be doing, yes

(Provided the temp is set low enough, not sure about eco-mode etc)

 

[naughtika]

another thought.. if you have openport cable 1.3 and evoscan, try and trigger the fan (hi and lo) using the actuators...


if these works.. in theory they are doing their job.. then I would look into other things like what the other guys have suggested....