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Discussion Starter · #1 ·
Removed a CPS from a yard car Sunday. After getting a chance to look at it I noticed rust had shorted the magnet. Flakes and filings had filled the gap and made a circuir that would permit the window to pass and close around it. Could this have been the reason the car was junked? Could it also be a reason for many of our CPS fails, where a thorough cleaning and de-rusting of the area would cure the issue. Opinions, please.;ol;
 

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Anti-freeze deposits from a slow Water Pump leak can stop them from working. I don't know if just cleaning them would work. I imagine metal filings could make them stop working, but I haven't observed that, even when the Harmonic Balancer comes apart and starts grinding the Oil Pump Cover and its bolt heads.
 

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The basic proximity sensor works by a change in( magnetic) flux around the core, a piece of rust or even thin steel will not effect it enough not to work. The same type unit is used for a tach signal in large trucks, it reads off the ring gear on the flywheel, and if you've ever pulled one apart after 500,000 miles it is filled with all kinds of junk, iron filelings, clutch material, and grease, and the tach still works fine.
The mass of the piece being "read" overwhelms the mass of the rust bits.
 

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Discussion Starter · #4 · (Edited)
Jim, what I have are rust flakes from the balancer. Exfoliation corrosion is the formal term, and there is enough in the sensor to act like a shorting bar on a horseshoe magnet. Also looks like exfoliation from the window assembly also. I grabbed the pump so I could have a drop in spare since I currently have 3 or 4 cars with the CPS, and noticed the condition. The 91 Vert that appears to need the CPS change is one I am going to look at more closely. Now you commented that you had seen failures due to coolant leakage. Was that replacement only? Or could you use electrical contact cleaner to clean and return to use?
 

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Discussion Starter · #5 ·
The basic proximity sensor works by a change in( magnetic) flux around the core, a piece of rust or even thin steel will not effect it enough not to work. The same type unit is used for a tach signal in large trucks, it reads off the ring gear on the flywheel, and if you've ever pulled one apart after 500,000 miles it is filled with all kinds of junk, iron filelings, clutch material, and grease, and the tach still works fine.
The mass of the piece being "read" overwhelms the mass of the rust bits.
This one was packed all the way through the gap, which is why the question. I also note that crank mounted sensors tend to be a coil type rather than the window type sensor we have.
 

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90% of the ones I replaced were under warranty. I wasn't about to try cleaning them to save SAAB a few bucks. No professional would risk doing the job twice and annoying the customer with a repeat failure either.
I have no idea if cleaning would work, but I've seen them running just fine after the Balancer had chewed through the Pump Cover and everything was coated with oil and both aluminum and steel filings.
 

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A couple of months after my balancer failure I had cps issues. When I pulled it all back apart the cps was filled up with metal filings (left over from the balancer eating the a/c pully) preventing it from sending a signal. After removing the debris my cps worked fine and in fact years later is still working fine...
 
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