variable/poor heating

[kennyboy]

just picked up my 993 and first thing I've noticed is the heating is more sensitive to town/open road driving than my last 993 - and also the overall heating efficiency is lower.

On my last 993 I could leave the heating dial in the middle and the air was just about right - and I didn't need to adjust it when I was in town or on the motorway.

On this one to get any sort of decent heat I need to move the dial to over 3/4's - near it's maximum...and it never gets really warm/hot even then.

And then when I'm in town I have to turn it down as the engine warms up.... The oil temperature is fine in town and on the open road - it changes as I'm used to with a 993.

Everything else works fine, air-con, fan etc.

Does anyone know if I have a problem here? - maybe heat exchangers.

I know air cooled cars have imperfect heating systems but this one is different enough from my last 993 for me to be concerned.

Thanks

 

[Sundeep]

Kenny

I'm just pleased I get some kind of heat this time of year, mine has a mind of it's own.....

I used to to get either very cold or midly warm, now I have midly warm and very hot, right now that works.. but needs looking into again ! []

regards

 

[kennyboy]

Thanks Maurice, can I do this test easily leaving the car in the garage - i.e. start it up for a few seconds and then switch off completely taking key out?

 

[zrcg1]

also bear in mind ..... if the heating feels poor, it could be your rear auxilliary blower fan is shot.

I've just had mine fixed (ready for the spring/summer!!) and there is a massive difference in the cabin heating.

A quick way to tell is if the front screen rapid defrost only runs at low speed. If the rear blower is gone, this cuts out the front fans when supplying hot air, running them in low speed. As a comparison, turn the fan position to 4 and temp all the way anti clockwise to the blue dot. The front fans will definately run in high speed.The rapid defrost should run at this same speed -

If not then 1) the blower is bust, 2) 30A blower fuse is gone, 3) the blower relay is faulty.

Hope this helps

Chris


PS. There are other ways to check, there are some good posts on rennlist regarding this.

 

[kennyboy]

Thanks Chris - printed that off, will try tonight. Seen the rennist stuff - looks excellent, gonna take that panel off.

To confirm if front screen defrost sounds slower than fan on max with min temp then probably rear fan?

Think I tested front defrost before purchase and was strong... will check again.

 

[zrcg1]

Kenny,

That is correct. Min Temp with Max fan should "sound" the same as screen defrost. That would confirm the symptoms and show your rear blower is not working.
The rear blower runs in two speeds, I think you can also check the motor is working by having ignition on (not started) with temp setting one way or the other, and fan position to 4.

Open the engine cover, the rear blower fan should at least run in low speed mode. - The rennlist post mentioned exactly how to check it, but I think this is the jist of what you can do to test it.

Relay and fuse - the fuse is in the fusebox on the LH side next to the blower in the engine compartment, the relay is in this box too. Easy to check the fuse, the relay can be swapped temporarily with the oil cooler/air con condenser relay as they are identical (but these are in the front fuse box!.......) to see if the fan at least runs in low speed.

If the fan does not work at all, this would definately explain poor heating.

Also I would think you would be getting some condensation in the cabin on damp days as the "default" air flow from the engine bay wont clear it.

Chris

 

[kennyboy]

Thanks Chris - plenty of things for me to check now, will try ASAP - didn't have much luck getting the panel off tonight even with some din radio removal tools..

Maurice - I assume you are referring to my posting of the same question elsewhere? If this is the case I apologise, I wasn't aware of this 'forum etiquette' (as opposed to manners of which I pride myself on being impeccable). I'll mention if do the same in future.

Couldn't hear the air sampling fan either Maurice - started the engine for a while and switched everything off, after various noises from front and rear of car had stopped (obviously not the fan) then couldn't hear anything at all - even when ear close to panel. Also tried with ignition on and heating fan off - only fan or 'moving part' I could hear was a faint whirring sound that seemed to be still feeding a small amount of air through the centre vents...even though main fan set to off......but nothing from the sampling fan?

 

[kennyboy]

Cheers - will do. Had a go last night not much luck, will try again tonight pushing from the back whilst radio tools are in place.

 

[John Maddox]

I know you have located the problem but whilst sorting this problem have a look at the pollen filters - mine were blocked with debris - cleaning them out increased the A/C flow quite a bit. Must replace them before the summer comes!!