Opened the engine lid today and noticed that the fan belt sensor had failed.
The wheel had frozen and it was being ground down by the fan belt. The dash
light had not yet come on. I had replaced the sensor two years ago and only
got about 30k miles out of it. Since it is about $80 and doesn't appear to be
very reliable or durable I decided to remove it entirely and rely on myself
to keep an eye on things. Besides, it appears to cause premature wear
on the fan belt. I'll replace all 3 belts in the next couple of weeks as part of
my annual maintenance plan. These old style v-belts only seem to be good
for about 20k miles so I change them each summer.

Here's a few pics from the job. In order to keep the dash light from coming
on it is necessary to connect the two wires together. To do this I opened up
the sensor and pulled out the connector with the micro switch. I cut off the
switch and twisted the wires together and then used some small heat shrink
to cover it. Then I tie-wrapped the connector to a cable so that it would not
be able to get into the path of the belts. Works like a charm.

-bruce

 

Interesting failure. For me, that's one sensor I wouldn't bypass, just saying.

 

I'm with flyingchappy, I just replaced my belts and the fan belt has a small bump on the outside so the sensor bounces. I thought of zip tying the sensor away from the belt for a micro second then thought, NAAA I'm taking the dodgy belt back.
That said, the stock setup is a silly way of sensing if the cooling fan is working, IMO an optical rotation sensor or an airflow sensor would have been a better and simpler idea.
BTW, I would have had a go at fixing that sensor, but that's probably just me...

Cheers
Alan

 

Disappointing that the bearing in the part would fail so soon.

Looks to me like the bearing is open on one side. That's good because you can lubricate it. That's bad because it will also allow in dirt.

I suspect dirt led to the bearing lockup and resulting failure.
Seeing this makes me want to run out to the garage and lubricate that bearing!

Has anyone looked into replacing the bearing with a completely sealed unit?

 

Brad, those bearings are sealed on both sides.

You can use a syringe and pump a dab of grease past the edge of the rubber seal into the bearing.

Note though that "sealed" bearings have a predetermined amount of grease put into them at manufacturer. An over greased "sealed" bearing can fail as well.

 

Ah. I thought I saw what looked like the edge of a bearing in bruce7's 2nd picture.
I should pull mine to take a better look at it.

 

Just install the RS single pulley. Then the sensor is not needed, if the belt brakes, the dash lights up like a X-mas tree.

 

Alex,
I am not suggesting that what you said is incorrect, but in this photo, that certainly looks like a ball bearing rearing its little head. If it is, they dont appear to be sealed to me.

Since the bearing is ng at this juncture, maybe Bruce could confirm if these are sealed on both sides, of it that is indeed a ball bearing we are seeing in the photo?

Since the bearing is already toast, maybe Bruce can, upon further examination and/or demolition; confirm if that is indeed a ball bearing we see in the photo, of a figment of my imagination.

If it turns out that the bearing is not completely sealed, then the design appears to be programed to fail at a less than optimal stage.

Thanks to Bruce for the post and photos...

 

I saw the shine of a metal edge, but those are sealed bearings...that have what appears to have a failed grease shield.

In most cases the dust/grease shields can be popped out and the bearings within their cage are in plain view. Some would wash out the bearing, repack them and pop the shield back in. Problem is, if the bearing has run dry, damage has already been done.

An open bearing would not last long in that set-up.

Bearings wear out/fail; you just replace the assembly or the bearing.

 

I might look into that and the serpentine belt mod.

 

I'll try and open it up tomorrow and see what's inside.

 

I was thinking the same thing about some type of sensor that had no moving
parts. Something like a toilet sensor that flushes after you've left. But the only
way to fix a broken sensor like this would be to replace the wheel. Looks to be
press fit. Don't know where you could get another wheel.

 

Looks like the wheel simply rides along the belt and it only serves to push the plastic piece into the mechanical switch.

Would it be possible to modify the mechanical switch and/or the plastic piece such that a lone bearing without the outer plastic wheel might suffice?

The bearing would get more revolutions, heat, and maybe something else that I'm not thinking of. But an inexpensive, easily replaced bearing could be a yearly or bi-yearly service item.

 

Not unless you change the diameter to something smaller.

And you can only make the wheel larger if it does not swing out and make contact with any moving item if the belt fails.

Are these failing ever year, two or five that we need to reinvent the wheel (no, not the actual wheel but the whole idea of needing something totally different)? Mine is in its 18th year and will likely fail in the near future. If it lasts that long, I'll just replace it with the same part.

 

Do you have a friend or neighbor with a lathe?