Please help-200 heats up, then cools down and gets COLD!

scirocco75 · 12-04-2006, 02:42 PM

It seems to heat fine for about the first 10 minutes, then the gauge starts to drop and it gets cold. In the fall I replaced the tbelt and t-stat, and last month I replaced the mfts. I had noticed a problem defrosting last week but with this sudden cold snap I realized the heat problem. I coiuld use some advise please.

qpower · 12-04-2006, 04:17 PM

Kneale Brownson · 12-04-2006, 05:34 PM

Have you checked the coolant plumbing to tell whether what you're seeing is a gauge issue? I mean, have you tested the temperature of the hoses. If they're too hot to handle for any length of time after the gauge starts to read cooler, you have a gauge/sensor wiring or sensor problem. If the hoses go from hot to cool and stay there, your thermostat is sticking open like qpower says.

jurq · 12-05-2006, 04:30 AM

There's a motor that opens and closes the flap to allow fresh/cold air to blend in with the heated, recirculated air. When it dies, it tends to stick open and let in too much cold air.

Have you tried using the HVAC head diagnostics?

scirocco75 · 12-06-2006, 05:09 AM

Thanks, no I havent tried the HVAC, guess I need to do so emore research. I think yopu may be right, the temp gauge doesnt drop until hwy speed, so I think it is just dropping because of the cold air, not the t-stat failure. And yesterday I ran the temp control from hot to cold and back again and heard a flap drop in the dash, suddenly it was blasting heat!

12-04-2006, 04:17 PM	#2
qpower Member Garage is empty, add now Join Date: Nov 2005 Posts: 4,927	replace t-stat again, sounds like it's sticking open once it does open

12-04-2006, 05:34 PM	#3
Kneale Brownson AudiWorld Super User Garage is empty, add now Join Date: Apr 2003 Location: Full-time Coloradoan now Posts: 3,337	Re: Please help-200 heats up, then cools down and gets COLD! Have you checked the coolant plumbing to tell whether what you're seeing is a gauge issue? I mean, have you tested the temperature of the hoses. If they're too hot to handle for any length of time after the gauge starts to read cooler, you have a gauge/sensor wiring or sensor problem. If the hoses go from hot to cool and stay there, your thermostat is sticking open like qpower says.

12-05-2006, 04:30 AM	#4
jurq AudiWorld Senior Member Garage is empty, add now Join Date: Jan 2004 Posts: 1,972	That is what I experienced when the fresh air blender motor went south on my 100. There's a motor that opens and closes the flap to allow fresh/cold air to blend in with the heated, recirculated air. When it dies, it tends to stick open and let in too much cold air. Have you tried using the HVAC head diagnostics? __________________ 1984 Scirocco MkII 1991 200 20v quattro Avant

12-06-2006, 05:09 AM	#5
scirocco75 New Member Garage is empty, add now Join Date: Feb 2006 Posts: 53	Re: Right on!-( fresh air blender motor went south) . Thanks, no I havent tried the HVAC, guess I need to do so emore research. I think yopu may be right, the temp gauge doesnt drop until hwy speed, so I think it is just dropping because of the cold air, not the t-stat failure. And yesterday I ran the temp control from hot to cold and back again and heard a flap drop in the dash, suddenly it was blasting heat!

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