Saab 900 classic convertible 1992 - heater

[beckyman]

The one unsolved challenge on my delightful car is to get more than a faintly warm response from the heater. Could there be an airlock? How should I proceed? I have owned the car for several years and because I do not tax it during the dark months I have never bothered to deal before with this shortcoming. I am now getting old and my blood runs thin and I could do with a little warmth. Other old Saabs that I have had in days gone by have all produced a superabundance of heat - in fact too much!

[TWR]

I am now getting old, I take it you are above doing the job yourself? if the car has been stood I would start by draining the coolant fully, back flush the system, remove & replace the Thermostat & Gasket, re-fill the system using antifreeze, start the car up in a ventilated area with the heater in the HOT POSTION & leave to run until the temp gauge gets up to its limit 1/2 way, leave the car run like this for app 20 Min's to make sure the system is clear of air, that should cure your problem.

[beckyman]

Thanks for the suggested remedy. Two further asks; at what point in the system would you introduce the backflush hose and secondly, is replacing the thermostat important if the car's motor has never overheated even when towing what is admittedly a fairly lightweight small caravan? And yes, I would get a friendly local mechanic to do this for me but I like to familiarise myself with the reasons for actions recommended!

[Graham-W]

There may be a filter, like a pollen filter, at the air inlet. Does the fan blow hard with no heat output or is there just low airflow?
Does it improve when the air is set to recirculate?

[TWR]

If the car was mine Beck, & as you have said, "warm response from the heater." I would start with the coolant system, over time the rad needs to be flushed & at the same time with bits circulating around the system it would be un-wise not to re-new the thermos at the same time, with respect to your car its 8 yr old & I would have thought never had this done! not everyone goes to these extreams, but there are owners & owners, It's obviously up to your self the way you go about it, but If I was asked about such a heating problem, that's the area I would go down. have you felt the heater pipes for been HOT? when the heater is on & in the hot postion, does it go HOT / COLD /HOT / COLD? If so, an air/lock.

[beckyman]

It blows less hard when set to heat than when set for cool air. I had not thought to try 'recirculate'; seems an odd thing to do with the hood down as we almost always have it!

[TWR]

What Milage do you do? is it to town etc? is the system getting hot enough? is it the same on 10>>20 miles regards the heat?

[Graham-W]

"It blows less hard when set to heat than when set for cool air."
Could be a partial blockage in the heater matrix. That's the outside of the matrix, not where the coolant flows. It sometimes happens when leaves and bugs etc. are sucked through with the air.
If it is this, the matrix needs to be removed and blown clean with compressed air. This could be quite an involved procedure so rule out other things before choosing this route.

[beckyman]

Thanks very much everyone. I will distil your wisdom and see what transpires. We use the Saab for holiday touring both with and without caravan. It fulfils this function perfectly. Some 2 - 3000 miles per annum.

[chas2008]

some of my earlier vehicles suffered with similiar problems, it was just a case of remove the heater matrix, or just the hoses and flush it through with a hose pipe to remove the accumulated gunk...worked every time.