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Hi. I am getting ready to change all my instruments. I am not sure on the tachs if I have alternator type or optical.

I was looking around the engine and think I have the optical....

I took picture of where I think the pickup is just need a positive confirmation...



Here is the tach from the back...



and here is a zoom of the sethings on tach...



Can somebody give me a positive ID...

Thanks,

JC

JC,

I believe that is the oil pressure sensor you took a picture of behind the starter. I have a tack drive hooked to the injection pump on the front side of the engine, and I have a magnetic hookup on the bellhousing. I believe the optical also goes on the bellhousing but I am not sure.

Brian

Thanks Brian. I am not sure. The oil pressure pickup is to the right of that pickup and I have a mechanical connection at that point also. That is the only pickup I could not identify.

I know temp pickup is by the water tank.
Oil is to the right of the one pictures.
And the mystery pickup is the one pictured.

What I need to know is what instrument to buy that will read from the available pickup. But I also think the magnetic is on the belhousing.

Thanks,

JC

What engine, what year. Get a serial number and check a parts book, it will give you all the tach drive information.
We went through the same issues when we changed from the big Vangaurd series tachs over to the ocean line tachs with Cummins Engines. I found through the parts book where and what the tach drives were with that information. In the end I ran off the alternator as it was set up with a tach drive.

Thanks. CUmmins 2506bta

Serian Numbers:

44318961
44566924

Thanks for your help!!!

JC

According to Aetna's website your engine "should" have a mag type pick up allready installed.

http://www.aetnaengineering.com/pdf/Eng ... meters.pdf

I just bought 2 digital Tachs from Aetna---on sale right now 50% off- $135each and there sender is only about $30 if yours does'nt work.

If your tachs still work a little, you can disconnect a probable sender (or alt.) to verify.

Like said earlier, sensor will be toward the end of engine //flywheel, cam,IP drive etc. but whether it is optical or magnetic I don't know how to tell the difference.

Mag pickup counts the flywheel teeth so it will be on the bell housing.

Altenator tach output will be marked ac.

Can't tell from those picks what the tach is cause it won't look any different between picup types.

If you don't have a flywheel pickup, yours is altenator.

Bruce,
Are the optical and the mag. the same type of pick ups? Or does there need to be some type of indicator (source) for the mag. pick up?

I went round and round with local salesmen trying to determine what tach would work with my engines. Finaly got ahold of someone in the assy. dept. for Aetna and they took care of me.

Had a good deal on some VDO's but was unsure of there compatability, and nobody I've spoken to seems to know very much about universal application to diesel engines.

My engines (Volvos) were set up for alt. pickup tachs. I would assume the output is not universal. So adjustment would be required, but I see no feature to adjust the tach. Is this likely, or are the tachs propriatory to the engine?