Date: Mon, 7 Sep 2015 15:32:06 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Where is temperature sensor & why does needle drop when
heater is on?
In-Reply-To: <55EDB616.7080003@williamsitconsulting.com>
Content-Type: text/plain; charset="utf-8"
The behavior you describe is quite normal. The front heater along with all those hoses have a significant amount of coolant there. When you suddenly open the valve that coolant is returned directly into the water pump where it then enters the engine and flows out through the thermostat mixing housing. The thermostat will take some time to respond and close to get the engine back up to temperature. Coolant temperature can vary significantly. The gauge movement is intentionally slow so that we don’t see or react to it. BTW if your gauge is reading correctly center of the LED to just above is normal. Your t-stat maybe keeping things a little too cool or your sender is a bit off. Likewise if you run down a long enough hill with the throttle closed and the fuel injectors cut off you will pump enough air into the cylinders where this will also cause the coolant temperature to drop.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Steve Williams
Sent: Monday, September 7, 2015 12:07 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Where is temperature sensor & why does needle drop when heater is on?
Hi,
Driving my 1991 Westfalia, I see a phenomem that I do not understand.
When my van is up to temperature, the needle sits approximately where everyone describes, just below the LED.
On a cool day (around freezing yesterday), if I turn on the front heater, the temperature guage goes down.
This, I do not understand. I would have thought the front heater would not affect the temperature of the water exiting the engine coolant jacket that significantly.
As I type this email, I originally thought that the thermostat would start restricting coolant flow to the to the front radiator as the temperature lowered... but I imagine that it's not cooling off sufficiently for that to happen, since I think these vehicles have around a 185 degree thermostat & the coolant must be much hotter than that. On that note, what temperature range would the coolant be running at when the engine is "up to temperature". I'm considering getting an Infrared Temperature gun as a new shop tool.
Does the behavior I describe above make sense, the front heater causing the needle on the temperature guage to be a bit lower (about 1/2 a needle width)?
Also, what would make a van run a bit cooler? On some cooler days, it seems the needle can't quite make it up to the "normal" summer time location even without running the heater.
I don't drive that much in the fall, mostly summer time & don't use the heater, so don't really have a baseline comparsion to work with.
Thanks,
Steve Williams
