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Date:         Thu, 10 Aug 2000 16:58:21 -0500
Reply-To:     John Rodgers <inua@hiwaay.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <inua@hiwaay.net>
Subject:      Re: Coolant temp warning light won't stop flashing - is my
              diagnosiscorrect?
Comments: To: "Fitz-Randolph, Douglas" <Doug@beaconmarketing.net>
Content-Type: text/plain; charset=us-ascii

Doug, the flashing light in the temp gauge in the instrument panel is the low coolant level warning light. It connects to the coolant sensor in the top of the coolant expansion tank.

On the sensor in the tank, there are two bare prongs that stick into the coolant. The sensor system operates on the resistance of the coolant between the two prongs. Several things can affect the resistance, and cause the llight to come on and blink.

1) Obviously, low coolant will cause the light to turn on and blink. When the coolant drops to the point the sensor prongs are exposed, the resistance between the two will increase towards infinity, and the light will come on. Solution: add more coolant.

2) If there is a crack in the sensor itself, that will affect the resistance, and the light will come on. I have had that happen to me twice. I just replaced the unit. Inexpensive, easy to do, available from Ron Salmon at The Bus Depot, Ken Wilford at Van-a-gain and others.

3) Coolant to water ratio is out of balance. I can't say enough about this. You have to have the right amount of coolant in the water for the resistance between the contacts on the low water level sensor to be correct for proper operation of the sensor and warning light. Of the top of my head, I think I recall that it must be a 50-50 ratio. If the coolant is old, it can have it's effect.

Coolant is no place to be chincy on the Vanagons. It's not THAT expensive, and good coolant helps keep the internal working of the cooling system free of corrosion and increases the life of the coolant pump. I now use bio-degradable DexCool (orange color) in mine - good for two years - , and I bleed the system with the tail end up. Procedure works great for me, and I don't have to hassle the bleeder valve up front.

Hope this helps a bit.

John Rodgers 88GL Driver.

"Fitz-Randolph, Douglas" wrote:

> Hello fellow list members - I am in need of some technical support for > my '90 Syncro 2.1. I just finished replacing my exhaust system (long > story, for another time) and now my coolant temp gauge warning light > begins flashing about 10 seconds after I start the engine and does not > stop. The engine can be hot or cold, same result. The coolant and > overflow reservoirs are both full. Any flashing I refer to is not the > self-test flashing when you start the engine - that occurs normally. > > I performed the following troubleshooting steps with a cold engine: > 1) Disconnected coolant reservoir sensor lead - no effect on flashing. > 2) Disconnected coolant reservoir sensor lead and bridged contacts - light > flashed constantly - no 10-second delay after starting engine. > 3) Disconnected single-wire temp sensor lead (bottom of thermostat housing) > - no effect on flashing, temp gauge does not register. > 4) Disconnected sensor lead (side of thermostat housing) - flashing stops, > engine idle increases. > 5) Disconnected sensor lead (side of thermostat housing) and bridged > contacts - no effect on flashing, engine idle decreases. > > Based on that I'd conclude that the sensor in the side of the thermostat > housing is bad. I don't think it's a wiring issue because bridging the > contacts did have an effect. What do you all think? There aren't any other > things that could make that light flash - are there? > > I did have to use a torch to loosen the exhaust bolts, and I was very > careful to shield everything nearby with pieces of sheet metal, but perhaps > the sensor is a little bit fragile and didn't like the heat? Just a guess. > > Assuming my conclusions to be correct, my next question would be... if I > unscrew that sensor, how much coolant is going to come pouring out? And > will I have to spend all day trying to get air out of the system? > > Thanks very much in advance. > > Doug Fitz-Randolph > Freeport, ME > '90 Syncro


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