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Technical How good should the heater be?

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Technical How good should the heater be?

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loserscar

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Hi,

I've had my Twinair for three years now but it's the heater time of year again, and I can't remember how good it was last winter.

It's a manual aircon model.

It seems slow to heat up, and needs to be cranked right up with the fan on two to get toasty.

As it's not that cold at the moment, then it might not be too toasty when the weather gets worse.

I ask because I'm tempted to flush the coolant, as it had some engine work earlier this year, and there could be some crud in the heater matrix.

Question two, though, is that it often, ever so slightly, mists up, and I have to crack a window to clear it.

I've checked that the scuttle panel under the windscreen wipers isn't holding water (it has two drain channels to keep clear), and it's fine.

I've got a horrible nagging feeling that the heater matrix might be weeping slightly, though the coolant doesn't seem to have dropped.

(I can't smell coolant in the cabin though.)

So, to recap, is the heater a bit wimpy?

And does the 500 cabin tend to have misting up issues?

It's a pity I've got a goldfish memory, or I'd remember what it was like for the past two winters.

Cheers.
 
The 500 heater is strong, heats well and should keep the windows mist free. It might struggle in high moisture atmosphere (cold rain), but all cars would do that. Putting the AC on should help to dry the air in that case.
Is the aircon still ok? Maybe that is the weak point?
 
I agree the heater is strong and gets very hot when allowed
I have auto climate control and it de mists in seconds
Though my old pop non aircon took a bit longer to de mist but still had a burning hot heater
 
All Cars with Aircon will mist up if you turn off the aircon over the winter. Aircon takes moisture out of the air, and the big aluminium evaporator will attract condensation which then gets blown on the windows as damp air as soon as you put the heating on. If you keep the aircon switched on then the cold evaporator will keep the moisture on the surface of the aluminium. and then it will drip off and drain out of the car. the best example of this is to put the air con on for half an hour or so, then switch the air con off with the controls set to the windscreen and watch the windscreen almost immediately fog up.

If the heating is poor then new coolant, a flush of the heater core and bleeding it all a-fresh will likely solve the problems.
 
Check your thermostat is good.

The temperature gauge should reach midway after about 5 or 6 minutes of driving. If it only gets up to half way after the car has been sitting stationary in traffic for 10 minutes, and then drops back down to 1/3 or 1/4 when you're rolling again, then the thermostat is weak. A new one is fairly simple to install.


Ralf S.
 
Ralf S. said:
Check your thermostat is good.

The temperature gauge should reach midway after about 5 or 6 minutes of driving. If it only gets up to half way after the car has been sitting stationary in traffic for 10 minutes, and then drops back down to 1/3 or 1/4 when you're rolling again, then the thermostat is weak. A new one is fairly simple to install.


Ralf S.
Click to expand...

In new cars like the 500 and the panda the heater is not controlled by the thermostat so the coolant circulates through the engine and the heater no matter if the thermostat is open or not
 
AndyRKett said:
In new cars like the 500 and the panda the heater is not controlled by the thermostat so the coolant circulates through the engine and the heater no matter if the thermostat is open or not
Click to expand...

I'm not sure I follow.

The HVAC system is just a heater (the engine block) and a couple of radiators (the car radiator and the heater matrix) all linked together by pipes.

The engine heats the coolant. The hot coolant passes into the heater matrix (either via a flow control valve or directly, for the heat to be regulated by the airflow through the matrix) and that heated coolant is then "cooled" to heat up the cabin.

When the coolant gets hot enough, despite the heater's effect of cooling it down, the thermostat opens and the vehicle radiator provides additional cooling of the coolant, as it's supposed to.

If the thermostat is allowing coolant to pass into the radiator before it's properly hot, because it has partly stuck open, then the coolant is being cooled by two "radiators"; the heater matrix and the vehicle radiator... despite already being cool. The vehicle radiator is also about 6 times the capacity of the heater matrix, so it would have a disproportionate cooling effect.

In that case the coolant will not get as hot/or as quickly as it should ... and the merely "warm" coolant that enters the heater matrix can't be turned into "piping hot" which is what the OP wants. I dunno how else you can get heat from cold coolant... unless there's an electric kettle type element inside the heater matrix.. ?


Ralf S
 
Best practice is to leave the heater & fan fully off until the engine has reached normal operating temperature, to minimise the warmup time. This both saves fuel and reduces engine wear.

Electric front screen heaters are great for clearing a screen; you get the double bonus of rapid demisting and a faster engine warmup; the increased alternator demand puts a bit of extra load on the engine.

I'd agree with those that are saying a thermostat that is not closing correctly will extend the warmup time, and in winter, may not even allow the car to fully warm up at all. Unfortunately this is rather a common issue on the 500/Panda, and may be happening in the OP's case. Not easy to spot as there's no other external evidence of the problem.
 
Last edited:
Ralf S. said:
I'm not sure I follow.

The HVAC system is just a heater (the engine block) and a couple of radiators (the car radiator and the heater matrix) all linked together by pipes.

The engine heats the coolant. The hot coolant passes into the heater matrix (either via a flow control valve or directly, for the heat to be regulated by the airflow through the matrix) and that heated coolant is then "cooled" to heat up the cabin.

When the coolant gets hot enough, despite the heater's effect of cooling it down, the thermostat opens and the vehicle radiator provides additional cooling of the coolant, as it's supposed to.

If the thermostat is allowing coolant to pass into the radiator before it's properly hot, because it has partly stuck open, then the coolant is being cooled by two "radiators"; the heater matrix and the vehicle radiator... despite already being cool. The vehicle radiator is also about 6 times the capacity of the heater matrix, so it would have a disproportionate cooling effect.

In that case the coolant will not get as hot/or as quickly as it should ... and the merely "warm" coolant that enters the heater matrix can't be turned into "piping hot" which is what the OP wants. I dunno how else you can get heat from cold coolant... unless there's an electric kettle type element inside the heater matrix.. ?


Ralf S
Click to expand...

You’ve spent a very long time explaining how a thermostat works, but if as you describe were the case then the problem would be obvious as the heater would go cold when moving and heat up normally when stationary. While the OP hasn’t described this, if it were the case it would be a very obvious symptom.

In the old days the thermostat would keep the water in the engine block till warmed up then the thermostat would open allowing coolant to flow into both the radiator and the heater core.

Any problems with the thermostat being stuck open would be obvious on the engine temp gauge
 
AndyRKett said:
Any problems with the thermostat being stuck open would be obvious on the engine temp gauge
Click to expand...

Thing is, it may not be stuck open; it just might not be closing fully.

There's a partial failure mode which is quite common on the 500/Panda. The rubber sealing ring inside the thermostat perishes, allowing some coolant to leak past the seal when it's supposed to be closed. The element still opens & closes normally, so it can create the illusion of a working thermostat if you're not aware of this possibility. The first sign that anything is amiss is that the car won't quite reach its normal operating temperature; you'll likely only spot this on models with an analog temperature gauge, as the drop in running temperature is literally the width of the needle. It gets progressively worse with time, and then becomes more obvious; replacing the thermostat is normally a complete fix.

A working but slightly less efficient heater that's slower to warm up from cold is entirely compatible with this failure mode.

If you're one of the types that monitors fuel consumption like a hawk, you may also notice a slight drop in economy; this was the first sign with my Panda that anything was amiss. Fixed by fitting a new thermostat; cost me less than a tenner.
 
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