RE Help diagnosing ABS OFF?

[Simon Allcorn <SALLCORN@softa.co.uk>]

>I am about to begin troubleshooting my ABS OFF problem. 

>Details: 87 5kcsTQ, pads and rotors are in good shape, light comes on after
>driving 1/2 mile, reset ABS, light on again after 1/2 mile. (diff locks are
>OFF). What preceeded this was the ABS OFF light would come on, I'd reset
>it-all OK for about a month. Stayed like that a few months, until the
>frequencies got closer and closer together, until what I have now. After
>following other similar posts, I now plan on checking the wheel sensors. 

>My questions:
>1) Before I start, should I get a new set of the plastic caps that go on the
>ends?

YES THESE PLASTIC CAPS ARE VERY IMPORTANT !

>2) Is there a way to check if the sensors are bad?

Yes, Read the output from each sensor;
1. Unplug the sensor (plugs are located ;
	NSF: below the battery tray.
	OSF: by the strut top
	OSR: in the boot under the carpet right hand side
	NSR: in the boot under the carpet left hand side
	(these refer to an 87CQ right hand drive)

2. Jack up the car so the wheel you are looking at can be spun.
3. Connect a volt meter reading AC, very small voltage (you are looking
for <50mV)
4. Spin the wheel and read the voltage.

The voltage should be about 30mV. (I know this is not how to test it
properly since the voltage from the sensor vaires it frequency and the
multimeter reads 50Hz only but it works!)
If the voltage is too low make sure the sensor is fully home with a NEW
CAP (I hit mine with a hammer.) The allen bolt that secures the sensor
is in a slot for adjustment - mine was practically at the end of it
adjustment (i.e. fully home)

>3) Anyone have any advice on anything else to have on hand?

When the ABS is on, DOSE IT WORK CORRECTLY ?
>4) The big one-Would anyone care to give a step-by-step on troubleshooting

>the sensors or narrowing down where the problem is?
See above (ish)