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

Peter S 993tt

Yeah - there is a little vent next to the hvac controls. If you pull the unit you'll see a fan attached at the back. Most likely the fan has stopped spinning.

kennyboy

Hi Peter

Thanks for the info - can you expand a bit on your advice - what are the hvac controls and what does this little vent do?

Is it some kind of temperature sensor....and do you mean this who unit pulls out?

The heater fan itself is working fine.

Peter S 993tt

Yes - you have a 993 correct? The hvac (heater ventilation air conditioning) controls are in that panel next to the stereo. You need the DIN radio removal tools to pull the unit out. Now on the left side of the unit as you are looking at it from the driver's seat is what looks like a little hole with a sort of grill molded into the plastic above it. This is where the unit has the cabin temp sensor (that's right built into the controller). Behind the unit there is a little fan that may have gotten unplugged - that prevents the air from being drawn in and the temp. measured accurately.

kennyboy

Thanks Peter - will check tonight.

Any idea where I can get these DIN radio removal tools? I'm in the uk

Peter S 993tt

Car stereo place, performanceproducts.com is where I got mine, dealer, etc. they should be fairly easy to obtain.

sidned

Any car audio store should stock these, or try Halfords.

There was a thread that explained how you can get this unit out with a couple of nails (I've used some small allen keys which works for me). Here's the thread:

https://rennlist.com/forums/993-forum/255051-heater-temperature-fluctuation-getting-cold-air.html

kennyboy

Thanks Guys - will try the thread or more likely visit halfords!

Ray Calvo

Might also crawl under the car while it's jacked up and check out the cable linkages to the heat exchnager doors (very front of the heat exchangers). Over time cables can die/break.

Peter S 993tt

993s don't have cables - they are servo actuated valves. The earlier ones were located in the trunk by the air handler. The later ones (like my 97) had them in the kick panels in the cabin.

JasonAndreas

The heat control boxes that are attached to the heat exchangers are controlled by differential pressure which is adjusted by the left/right temperature mixing flap servos up front.

Peter S 993tt

Hey Jason - where are you I noticed the Berkshires - that's where my baby is.

JasonAndreas

I'm about 20 minutes from Pittsfield. Is your 993TT silver?

Peter S 993tt

I'm around Chatham NY - no it's black on black. Actually it's buttoned up for the winter - though I'm going to do some work on it this weekend - change the nitrogen bottle for the clutch, new pentosin, new air supports for the hood (tired of getting my head banged when I check the oil)

In the spring we should meet up in Great Barrington.