tach sensor alternative?

[84TD]

Anybody ever tried one of these instead? Not sure if it would fit a serp belt setup with the vacuum pump up top but should work for the older trucks, I think the threads are right.

http://www.summitracing.com/parts/sww-82646?seid=srese1&gclid=CJGE7KqGyLsCFax_QgodAzUAZw

 

[bob_442]

I bet that would work as a cheaper alternative to the aftermarket tach sender that Dakota Digital sells -- it uses the teeth on the flywheel whizzing by, a fraction of a millimeter past the sender to generate a signal from which the RPMs can be determined. It looks like exactly the same part, except plastic instead of brass, and with the plug instead of a pair of threaded posts.

Bob

 

[FarmerFrank]

from my understanding as long as its a mag pic up with 3/4-16 threads you are golden. On big truck speedo's i was always thought screw them in until it touches the gear then back it out a smidge so it doesnt rub.

 

[wildman7798]

Isn't the issue though calibration of the tach / sender ? You would require a know source of the engine RPM and then calibrate the tach to that value when hooked to your mag pickup. My research came up with the Isspro balancer pickup as the most cost effective. I know you have been working on this for some time TD. Did you see the latest link on our forum this week with the Isspro cleanup sale - they have some 2" diesel tachs for like $50. You could be in the whole thing for like $150 and have all new if you went that route.

 

[FarmerFrank]

Isn't the issue though calibration of the tach / sender ? You would require a know source of the engine RPM and then calibrate the tach to that value when hooked to your mag pickup. My research came up with the Isspro balancer pickup as the most cost effective. I know you have been working on this for some time TD. Did you see the latest link on our forum this week with the Isspro cleanup sale - they have some 2" diesel tachs for like $50. You could be in the whole thing for like $150 and have all new if you went that route.

Thats more just the tach side of things. The sending unit does not care if its counting 1 tooth or 500, just so there is a gap for the magnet to pulsate and create the signal. Now finding a tach to reconize 106 pulses = 1 revolution of the engine is where most people have trouble. Tachs in older semis have dip switches you set i.e. "dip switches 1,4,6,9 set to ON = xx gear tooth count" i have one for a Volvo truck that will reconize a 106 count that i plan on putting in one of these days. I got lucky becuase it came with the instructions

 

[dunk]

I just bought a new Ford tach sensor, they are still available so why not just get the correct unit? It's metal and has the correct depth already, as well as more compact than that long adjustable unit.

 

[84TD]

I just bought a new Ford tach sensor, they are still available so why not just get the correct unit? It's metal and has the correct depth already, as well as more compact than that long adjustable unit.

The reason is if I could spend the $70 and know I was good for life that would be one thing but this is my second bad one and you hear of folks with bad ones all the time. For the limited number of idi's on the road its seems like too high of a failure rate. It should be a very simple device, there are lots and lots and lots of applications for the exact sensor design in ABS, crank pos, cam pos, VSS and prob a bunch of other things and these are not going bad all the time.

I found this thread http://www.thedieselstop.com/forums/f30/expensive-tach-sensor-284464/ and it made me start thinking about alternatives. I could prob use this cav CPS and be good for life!

 

[wildman7798]

Didn't realize they were that high a failure item. When I researched all the tach stuff prior to deciding to go factory vs. aftermarket I read of very few failures. There must be a ton of those Ford sensors at pick and pulls every day. I paid $30 for a used one on ebay and so far so good. The other thing that comes to mind is if the failure rate was that high on these surely companies like Standard, Echlin, Borg Warner would have jumped into the replacement market. I guess the frustration of wasted money drives us to look for alternatives but a 3/4" 18 die for $5 is not going to happen in the real world.

 

[jaluhn83]

Any of the ISSPRO programmable tachs will work - they're setup to take at least 255 pulse/rev and maybe higher than that.

I don't think these are that high of failure really, rather I think it's cause we're fixing 20+ years of wear & tear. Sort of like engine rebuilds - we see a lot of engine problems due to age and what we're doing with them but that doesn't mean the engines are bad, just the demographics make it look that way.

I think also many of the problems with the sensors are damage due to work on the engine/whatever - the location is somewhat exposed and it's easy to crimp or break the wires.

The stock sensor location is interesting as well - it's much further out from the gear than I would have expected - I measured it at around 0.075", when 0.030" is much more common for these type sensors. Being closer to the flywheel gives a stronger signal. I think this is much of the reason why it's common to have faulty readings at low rpm, and if you could get the sensor closer it would solve some of these issues. I machined the new sensor on mine down about 0.015" and it did seem to help some with the accuracy of the tach (aftermarket isspro) though now I have high rpm inaccuracy.

If you really want to quick and dirty tach feed tap the alternator output before the rectifier and run an alternator tach. Not as accurate, but cheap & easy.