Tach

[unclebilly]

Does anyone know what king of signal is sent to the dash for a tach? My industrial / marine diesel tells me that there are basically 3 types of tachs for diesels...

Mechanical, Alternator Tachs, or Optical / Magnetic tachs.

I understand that the 6BT's in these trucks have crank angle sensors - I'm wondering if the signal from these would trigger a normal gasser type tach?

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91. 5 CTD 4X4, 5" Stacks, Tweaked Pump, 33" Boots (in the summer), Unlimited Slip,
<P><B><A Big, Bad Dodge

 

[boatpuller]

This is what VDO told me, see prior post; https://www.turbodieselregister.com/ubb//Forum13/HTML/000059.html
If that doesn't get you there, do a search in the 1st gen archives for tachometer, it will bring up a posting titled Tachometer won't work. I still haven't taken the time to play with the tach anymore.
Caleb


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1993 LE W250 4x4 CC,Auto,3. 5's,LS. . Diamondplate,PowerWagon injectors,K&N,Egt,Boost,trans temp VDO Vision series, BD 3 1/2" Exhaust, 16cm housing,Mag Hytec Diff+ Trans pans,Transgo TFOD shift kit,Roadmaster Active Suspension.

Caleb Reese (per forum guidelines)

 

[boatpuller]

also https://www.turbodieselregister.com/ubb//Forum2/HTML/000352.html

 

[Jones]

Uncle Billy,
The only set-up I've seen on Dodges so far have been magnetic. My '89 uses two small magnets epoxied on 180 degrees apart. When I got my replacement damper it had two notchs cut into it 180 degrees out but the principle is still the same, a break in the magnetic field.
I'm not sure that there aren't different pick-ups for magnet and slot styles 'cause the slotted style uses a pick-up on the front cover and mine uses the pick-up on the pan rail. Didn't matter though for me, I just epoxied a couple of small household magnets in the slot and it seems to work just fine.
Hope this helps, Jones

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Jones
'84 Ramcharger w/CTD, non-gated 12, torqflite, NP205, Dana 60 and 70 w/ 3. 07s. Straight piped 3" to x-member 4" the rest of the way.

 

[unclebilly]

Wow, thanks.

Did you ever get the VDO working or just go for the Mopar job?

Scott.

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91. 5 CTD 4X4, 5" Stacks, Tweaked Pump, 33" Boots (in the summer), Unlimited Slip,
<P><B><A Big, Bad Dodge

 

[boatpuller]

I haven't got the VDO to work yet, it became a very low priority to me, one of these days... ..... I need to borrow a friend Mopar tach to see if it works.
Caleb

 

[Lil' Dog]

My tach is a Motorola alternator tach and is works great. Easy to calibrate and to install, no magnets no fuss. Just hook to one of the fields on the alternator, and the sheave ratio is about 2. 38:1. Simple as pie.

J-eh

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Jason Hoffman
Lil' Mack - 89 D250LE 5 Spd 3. 54 LSD Reg Cab. K&N,"tweaked pump", BD Injectors, Banks Pyro/Boost, 3. 5" Exst tail section straight. E&M Custom seats. Bosch H4, PIAA 80W/80W HdLites. 100W Drv,55W Fogs.
237,500 miles (380,000 Kms) 7850 Hrs. Cummins Power Booster member.
The Original Turbo Diesel

Lil' Mack Pics 07-00

 

[Paul Herioux]

Lil Dog,
Do you have a part number and/or where to get for that Motorola tach? My local parts man hasn't found one for me yet. Also, do you know if it will work with the 97 Nippondenso altenator that is now installed on my truck?
Thanks.

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89 w250, 47rh trans, cleaned up exhaust, Dynomax bullet muffer, 3" lift

 

[Lil' Dog]

Paul

I do have all the info on the Tach, but Motorola hasn't gotten back to me with any particulars as I don't have a manual. It should work on any alternator as they all have the same internals.

I'll email you the info today.

J-eh

 

[boatpuller]

I went to a local(very knowledgeable) starter and alternator rebuild shop and they told me that some alternators came with a tach connection on them but that it wasn't just the field lead, I hope you're correct Jason, if you have any more info on the way it is connected in your truck please share it with us.
Thank You!
Caleb

 

[Lil' Dog]

Well, maybe my terminology is not correct.
Basically when I take of the rear plastic cover, metal on the new alternator, there is the main "bar" of all the 4 "field??" connections. I believe this bar is the bridge rectifier for turning the AC voltage into DC. They each have a screw connection, the rectifier was in the rebuild kit I was going to buy orignailly. I had to take apart the old one to hook up the new one, up to this point I didn't really understand how it hooked up. I should test this lead to see what it gets, but I'm pretty sure its a once-per-turn idea so long as you know the drive ratio you can use it. The Tach doesn't have switches for ratio but rather a pot to adjust the calibration.

I should have taken photos when I swapped the alternator 2 weeks ago darn it all. I just took the core back yesterday, Doooh!!

I can try to take some photos tonight with the digital camera, it might be hard to see though.

J-eh

 

[boatpuller]

Thanks Jason,
I think I'll be able to figure that out, won't get to it until sometime next week, I have to work this weekend, the shop told me that some of the alternators came with an external post for a tach, but if I can hook up to a lead inside that will work ok also.
I have to figure out where I left the instructions for my VDO tach so I can figure out how to adjust it, if I remember correctly it was adjustable for a number of pulses per revolution.
Thanks for the help.
Caleb

[This message has been edited by boatpuller (edited 03-14-2001). ]

 

[Lil' Dog]

Well here are some photos of the tach. I hope it helps.

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J-eh