a stuck open thermostat that prevents the engine from reaching full operating temp sure WILL cause poor heater performance. That's obvious I hope.

on ALL cars, on all water-cooled cars and vans, with nary a exception, that I have ever seen, in working on cars starting in 1964, and working on them nearly full time since then..... every heater system I have ever seen, takes coolant straight out of the engine, at all time, regardless of coolant temp, and sends it straight to the heater core/s.

that means if it's cold out, when you fire up the engine, if the coolant is say, 30 degrees F, and your heater temp valve is 'on' ....30 degree coolant will be flowing through your heater core.

that also means if the t-stat is lame and the highest temp the engine will run at is say, 150 .......the coolant going to your heater core/s won't be hotter than that.

here's an important trick, I hope most cold weather vanagon operators know - if the heater temp valve ( and thus coolant flow ) is full on dead cold, it will help cool the engine, and make getting up to full operating temp take longer, In some cases, Much longer.

there have been factory bulletins about this. Subaru, for example, found that people would have their heater on full from dead cold, and the engine never got up to full operating mode, and never went into closed loop operation even.

so......temp lever no higher than half on, until some temp is showing on the gauge, then move the temp lever to full on. The engine will get up to full temp sooner.

the statement that the closed t-stat sends all coolant to the heater core is partially true, but it's not because of the status of the t-stat. Heater core flow is determined only by heater lever position, regardless of what the t-stat is doing. The t-stat doesn't even know what position the heater temp control lever is in - all it's trying to do is prevent coolant flow to the radiator until it's up to operating temp. And as I said, if the heater is full on dead cold, it will be much harder for the t-stat to get the engine up to full temp. If it's cold enough, and the load on the engine is low enough, ( like driving downhill with a cold engine ) and with heater/s full on, it might not ever even reach full temp, which is really bad for the engine, and wastes fuel.

you want a good t-stat in there, and don't try to get heat out of the heater until it's mostly up to operating temp.

vanagons are so fun ! and so fixable too. Scott www.turbovans.com

----- Original Message ----- From: "Edward Maglott" <emaglott3@GMAIL.COM> To: <vanagon@GERRY.VANAGON.COM> Sent: Thursday, January 07, 2010 10:05 AM Subject: Re: No heat at stoplights.

>I believe the Thermostat in closed position sends all flow to the heater > cores. That's why water cooled VWs have been famous for their great heat. > Edward > > > On Wed, Jan 6, 2010 at 2:26 PM, Don Spence <dkspence@telus.net> wrote: > >> Thermostat is highly unlikely. It's function is to close and curtail >> circulation within the engine until operating temperature is reached >> then slowly open to permit circulation to the cooling/cabin heating >> system. If it fails closed, the engine overheats and will be >> apparent on your temp gauge which has it's sender in the thermostat >> housing. If it fails open it slows the engine coolants rise to >> operatingt temp. >> >> Your situation is one of circulation (as in little circulation at low >> rpm) not temperature as regulated by the thermostat. >> >> >> On 6-Jan-10, at 11:42 AM, Automatic digest processor wrote: >> >> Date: Wed, 6 Jan 2010 13:19:35 -0500 >>> From: David Prendergast <dprendergast@TRIAD.RR.COM> >>> >>> Subject: Re: No heat at stoplights. >>> >>> The coolant bottle is full with no leaks anywhere, someone earlier >>> said it may be the thermostat and the symptoms do match (thermo is >>> about 4 years old). It blows hot out of both rear and front heaters >>> until I stop at a light then it blows cold. Not really a big deal >>> since the weather is relatively mild here in central North Carolina. >>> >>