Fan Belt Sensor Wheel - Need Help
 

Hey,
Yesterday my "broken fan belt" light came on during the drive home and I quickly pulled over and checked the belt. It was fine except the outer braid seemed to be a bit worn. More importantly, the sensor wheel was noticeably smaller in diameter. Now look at it after 1 more day of driving!

I'm not ready to part with almost $100 to replace this whole part. I have a new belt and that will go on this weekend. Funny, but the business side of the belt looks great!

Anyway, I want to make a new sensor wheel out of aluminum (practicing my lathe skills). Could someone please put a recently calibrated Starrett caliper on the wheel you have and give me the diameter. OK, a Brown & Sharpe caliper will do if it's clean. Alright, I'll even take an old Craftsman caliper. Heck, take the Stanley tape measure out of your brother's tool belt and give it a go.

Thanks,
Mark
http://forums.pelicanparts.com/uploa...1205451662.jpg

Hi Mark,

I say you have definitely lost a significant part of your idler wheel. My idler, on an '89 C4 with 51,000 miles, measures 1.415" hot, as in I just returned from driving it a spirited 35 miles!
That should get you in the ballpark.

Lynn

A lot of people loose this part by going with a one belt conversion. And none of the 3.6 converted early cars will retain this either. There should be plenty of these around used for cheap. I'd do a search ad here and check Ebay.

Only of course if your lathe fails you ...

George

The reason yours failed is probably that the little ball bearing got tired. I would either get the stock part or do the single-pulley conversion. Same $$$

Fan Belt Sensor Wheel
 

ischmitz,
How right you are. I pulled the "Sender" this morning and the little bearing was quite stiff. I found a new on one ebay for $1.95, I think they use these 6mm x 19mm bearings in RC cars. Anyway, I think I will make a super trick aluminum wheel to go over the bearing. I send updates as I make progress.

Thanks,
Mark

Fan Belt Sensor
 

Is there any benefit to a single belt setup? I see the obvious benefit of deletion of one belt, a bearing, and a set of pulley halves (weight?). But does this outweigh the benefit of having a two-belt system. The benefit of being able to delete the A/C from the car easily. Or the redundancy factor?

Is there a difference on the fan speed before and after the single belt conversion?

Thanks,
Mark

For me, the single pulley was an issue of improved reliability in a track car. I was shredding alternator belts with regularity before the switch; I have ~10 track weekends on the first belt since the conversion. If a belt does break now, it is also supposed to be easier to replace (although I haven't verified this yet).

My understanding is that the fan speed is the same, but the alternator is slightly slower. Again, for a track car this is fine.

There is a wealth of detail in this thread:
http://forums.pelicanparts.com/porsche-964-993-technical-forum/311979-rs-pulley.html

My sensor started squeaking a while back. I tried to extend its life by lubing the bearing. That only lasted a short while. I tired a few times, then gave up and bought a new sensor. No problems since then. I had a choice: futz with the old part forever or fork over $100 and be done with it. I chose the latter.

You can also do without the sensor altogether. Just remove it, and either short the connection or open it, whichever condition it is in when it is sensing the belt, I forget.

The single belt will make the alternator run a little slower. This is fine unless you are sitting in dense trafic for prolonged times in sub-zero temperatures running all sorts of accessories such as heated seats, heated rear window, all lights, big stereo, etc.

In other words there isn't really an issue with this conversion. On the plus side you will get a little more power (yipee) and more reliability because of a much simpler setup.

I would not simply short the sensor - if you do this and your stock fan belt breaks you won't notice until your engine has overheated!!! With the single pulley conversion your alternator light comes on just like in the old days.

Ingo

I updated my twin belt setup to a single ...when I started eating belts every 100miles ....car has been fine ever since .....even in traffic etc .

see page three of my thread