Ok, I've looked at the Bentley -- first of all, there's no mention of a resistor pack in the schematics for any year that I looked at except possibly the '83/84, where there's an ambiguous little symbol that could possibly be a resistor. I've an '84 myself, maybe I'll look sometime. :) Anyway, the current path for both low-speed and high-speed starts at fuse S13, 30 amps. The low-speed power and relay power is supplied from terminal C7 on the fuse block to a R/W 2.5mm to lug 3 of the thermoswitch. There's a spade-terminal connector in this wire, somewhere under the dash. Lug 2 of the thermoswitch feeds the low-speed winding by a 2.5 mm R/BK to the motor harness. (Motor connector: 1 low 2 high - ground 2.5 mm BR). That path is enough to diagnose a non-running fan, as the relay is used only for high-speed. However, it is perfectly safe to short all three lugs of the thermoswitch together, which will also activate the relay and the second winding. If you have a 12v test light, continue by testing terminal 3 of the thermoswitch. It should have 12v at all times. If not, it's the fuse or the wiring btw the fuse and the thermoswitch. With the thermoswitch shorted, the motor (+) lead(s) should have 12v. If so, then hook the test light to 12v and check the motor (-) lead. It should be grounded, so the light should light again. This is actually the likeliest problem after the fuse, as it is common to both motor windings. The motor ground goes back to a multilug cluster behind the relay panel. If you don't have a test light, they're fairly cheap and very useful, and the fancier ones can pierce a wire's insulation. Otherwise you can use a sewing needle or pin to test as needed. The needle is better as it makes a smaller hole in the insulation. You can make a test light with any small socketed 12v bulb, just run out a length of wire with a clip from one side, and a short length with a point of some sort on the other side. A test light is preferable to a voltmeter for this kind of tracing, as the light puts enough load on the circuit to show some open circuits that a voltmeter might pass as good under no-load conditions. Any preguntas, just ask... david At 13:32 3/28/99 -0800, Rubatoguy wrote: >Does anyone have a way to diagnose the radiator fan not coming on? >(3-speed fan) > >I understand that it could be the relay, the thermoswitch or the >resistor pack. I can't seem to find anythin in Bently as far as tracing >the problem or even testing these components. > >Anyone know how to do it? > > > >Thanks >Todd >'88 Westy |
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