Date: Tue, 31 May 2016 22:49:49 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Radiator fan- '91 Carat
In-Reply-To: <CA+az7_7V50p5n9H2wwJwBsZMFKR+xnFV3Oa1C9r9BxL=XmOYyQ@mail.gmail.com>
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I know it's not Friday but I have to wonder. You have had both an engine and then a transmission installed by servicing facilities. Neither one tested and made sure the cooling system was working properly? Were they instructed not to bother or they just threw those major parts in and left you to go for it? I can’t imagine warranting anything not knowing if the cooling system is working. Rant over!
Now go get the Bentley and look over the wiring diagram for the fan circuit. There are some variances but if you have late model with AC here are the components to check out.
For the engine cooling you have the power supply for the control circuit (Fuse box) and the radiator cooling low speed. Then there is the radiator temperature switch, the speed resister, and of course the motor. For high speed radiator cooling there is another relay mounted above the fuse box. This gets its own power feed from the battery and has a fusible link. When called for by the radiator temperature switch it puts the fan in its highest speed by completely bypassing the resistor.
For the AC there is a contact on the compressor relay that also operates the radiator fan at its lowest speed. Then there is a multi-stage pressure switch or even a separate on that when needed will operate the relay in the fuse panel (#5?) to parallel the other winding in that fan resistor and increase the speed significantly. It will roar a bit. On some continued pressure increase will cut out the AC compressor.
So these are the major parts. For testing begin with the fuse in the panel. When this is gone the high speed circuit is also crippled. The fan resistor and temp switch are common failure items especially if the AC is used a lot and the fan motor is tired. It is not enough that it works. It needs to be tested not to have excessive current draw. A bad fan motor will eat the thermo switch and resistor and when bad enough will destroy some wiring.
Then jump the connector for the fan switch. Use a meter to determine which wire has the power, one of the ends. Connecting that power to the center will get you low speed. Not working, take the meter to the resistor. Power on one side, not the other 2 wires, bad resistor. Replace. Power both sides go to motor. Power there, check ground for motor. Common for that wire to fail where it is attached to the body. Ground good! Check for voltage across the motor. Now power go back to previous steps. If you have power there and no fan action you need a motor.
After you the radiator cooling sorted out you then need to check the AC fan control. If the compressor is running the fan should be also. If yes good. If not again check the resistor for power. No power you will need to go back to the AC controls. Power going in and not out, the resistor again. Have fan working low speed, need to check for the next fan speed. Block the condenser with some cardboard. With AC running let it build up some pressure. Give the engine some throttle, you should hear the fan increase speed. Ideally this should be done with gauges connected so you can see at what pressure the fan speeds up, somewhere around 275psi.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Rodgers
Sent: Tuesday, May 31, 2016 5:13 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Radiator fan- '91 Carat
How is the radiator fan turned on and off, and just how is the speed adjustment ccomplished?
At the moment, my fan simply does not run. I want it to run, and run correctly.
John
