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trouble shooting my tach  Rating:  Rating
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 Posted: 01-18-2013 09:06 pm
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JHDSL
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Anyone have any thoughts on what to do to trouble shoot my tach. i have a 1974 JH and the tach looks original. Its dead all the timeother than a recent highway drive when it came alive for a few minutes, stuck at 4000 and then died. Where to look in the engin bay for wires and termination point? and  - Would anyone know the red line speeds for 1st, 2nd and 3rd gears? Thanks

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 Posted: 01-19-2013 01:57 am
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Jensen Healey
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Welcome to the forum!

Please post your vin number and, if you can see it above the starter, engine number to the VIN database. The Jensen historian Ric Calver keeps track of running cars, junked cars, and all things Jensen.

The current for the ignition flows through the tach and the tach "reads" the electromagnetic field around the wire.

If the car is running, we can assume the problem is in the tach itself.

The speed per 1000 rpm are listed in the repair manual. do you have a 4 speed or 5 speed transmission?

Cheers, Kurt

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 Posted: 01-21-2013 11:42 pm
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JHDSL
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I emailed richard and he has my vin number, and I'm looking for teh engin number. An update on the tach. I was on drive yesterday and late in the run it starts working, not working very well but working. Is there anything else I could check? Are there moving parts inside that i could clean or lubricate? thanks

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 Posted: 01-23-2013 06:30 am
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answerman
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Mine hasn't worked since I got it, doesn't move at all. Curious to see what you come up with. I've established that it's not the wiring or ignition in my case.

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 Posted: 01-23-2013 01:16 pm
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JHDSL
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I believe it's the tach itself. I guess thenonlynway to test this is to buy a replacement. Not suremim there yet. I will keep this post going.

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 Posted: 01-24-2013 08:13 pm
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dwalls1
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MOMA in Alburquerque, NM can fix it for you. They can also modify it to work with the Pertronics ignition. I am sorry I do not have their contact information at hand, but it should be readily available in this modern age.

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 Posted: 01-24-2013 09:49 pm
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JHDSL
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Mo Ma Manufacturing - instrument repair
13211 Second Street. NW
Albuquerque, NM 87102
Ph (505) 766-6661 - Fax (505) 766-5419
momanm@aol.com

Thank you - I will give them a call. Does anyone have any tips for removing the tach?

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 Posted: 01-24-2013 11:34 pm
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Frank Schwartz
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I have a couple of Tachs from Junked JHs...they all look the same to me...and if you are using the standard ignition and not Pertronics or something else, they should work just fine. So if anyone wants one, please contact me off this site...at mfsjr2@comcast.net
Frank Schwartz

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 Posted: 01-25-2013 10:35 pm
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answerman
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JHDSL wrote:Does anyone have any tips for removing the tach?It's actually pretty easy... assume the Lotus position with your head shoved under the dash, remove 3 wires (I believe) and then remove the two thumbscrews that pull it back against the back of the dash.  Comes right out the face of the dash then.

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 Posted: 01-26-2013 12:06 am
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JHDSL
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Thanks - I see there are two screws on the face od the dash. Do these come out, the dash face comes of and then its as you explained?

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 Posted: 01-26-2013 08:58 pm
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Gary Martin JH 15371
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The dash cluster (or binacle as the Brits call it) with all four gauges will come out, but it can be difficult if it has not been out recently. On the back of the cluster in the center there is a metal rod that slides within a clip to hold the cluster. After years it gets rusty and prevents cluster from coming out easily. If you can clean and lube the rod from under the dash first it will make it a lot easier. The only other things to remove first are the two screws you see from the front, and the speedo cable. It might just be easier to remove the tach and not the whole cluster.

My car has the Pertronix. The tach works most of the time, but it jumps around a lot. I think I need to get it modified. Thanks for the info on MoMa Instrument Shop. Anyone know of a similar shop up here in the Pacific NW ?

Gary  

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 Posted: 01-28-2013 06:46 pm
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answerman
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JHDSL wrote: Thanks - I see there are two screws on the face od the dash. Do these come out, the dash face comes of and then its as you explained?I don't think we are talking about the same thing.   The tach is mounted in a hole in the dash.  If you disconnect the wiring, and look at it from the back/underneath, you will see two knurled nuts that hold clamps that pull the tach back into the face of the dash.  If you remove those, from behind you can push the tach right through the hole (toward the steering wheel).  It pops right out.  You don't need to remove anything else.

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 Posted: 01-28-2013 09:08 pm
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JHDSL
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OK - this makes more sense. Thanks for the clarification. I hope I can fit/contort myself under the dash :)

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 Posted: 01-29-2013 03:44 am
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Mike Aubuchon
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I found it easier to remove the drivers seat. With the seat out you can lay on your back and reach under the dash. Still a tight squeeze but at least you can see what you are doing. There is a lot of wiring in a small area behind the dash so be careful not to disturb the other circuits.

Mike

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