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| JH TACHOMETER VS PERTRONIX IGNITION | Rate Topic |
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| Posted: 08-08-2010 04:30 pm |
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1st Post |
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timeforwalkies Member
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Anybody had this problem? I have the Pertronix ignition system installed and the car runs great. But now the tachometer show zero rpms. Even went to the trouble of installing a second one that I knew worked from my donor car. Still zero. So what the heck is wrong here? Thanks Clif Found it and it looks like mine. Didn't remember what the answer was and couldn't find it through search. If anybody has more to add that would be great. Sometimes new solution come up. Last edited on 08-09-2010 04:50 am by timeforwalkies |
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| Posted: 08-08-2010 06:21 pm |
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2nd Post |
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Art DeKneef Member
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Search the board here. I believe this has been discussed here a couple of times before. From my fuzzy memory on this it has something to do with the tach needing to be rebuilt or swapped for a different type due to the different electronics of the Pertronix. Or it has something to do with the ballast resistor. If I remember correctly this is something I think Pertronox is aware of and calling them may help resolve the issue. I'm sure someone else will have the correct reason and will pipe in. Art
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| Posted: 08-10-2010 04:31 am |
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3rd Post |
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timeforwalkies Member
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OK. So I finally figured out what to do via the Pertronix website, but not how to do it. They say "...relocate the tachometer trigger wire to the white wire from the Second Strike box". Very clear if you know which wire on the tachometer is the trigger wire, that is where that wire is located under the hood. Anybody know which one is which? Thanks, Clif
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| Posted: 08-10-2010 01:56 pm |
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4th Post |
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Jensen Healey Super Moderator 
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It's a white wire (on some cars white/ slate) connected to the ballast resistor on the firewall. Kurt
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| Posted: 08-10-2010 03:56 pm |
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5th Post |
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timeforwalkies Member
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Thanks Kurt. However, I don't see anything on the firewall that has a wire connected to it. Several wire flitting around the coil. I hear there may be a difference on 74 1/2 cars, but still that doesn't help if you don't know what the difference is. Thanks again, Clif
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| Posted: 08-10-2010 10:00 pm |
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6th Post |
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Gary Martin JH 15371 Member
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OK, the Pertronix has two wires, a red and a black. The wire coming from the tach (usually the white/slate wire) is the same wire that provides power to the ballast resistor next to the coil, or if your car does not have the ballast the wire will go directly to the + or positive side of the coil. If your car has the ballast, the white/slate wire will connect to one side of the ballast, the other side of the ballast goes to the +/positive side of the coil. The tach wire is also the ignition wire from the key. Some cars use two wires for Ign and Tach, but the JH it is just one wire. Hook the red wire from the Pertronix to the same location on the ballast resistor that the white/slate wire from tach/ign connects to. If no ballast, then connect to the + positive side of the coil. The black wire from Pertronix connects to - negative side of the coil. This is how my 74 is hooked up (I have the ballast resistor). Tach works on my car, but it jumps around at times. Most of the time it reads correctly. Gary
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| Posted: 08-11-2010 12:37 am |
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7th Post |
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timeforwalkies Member
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Thanks Gary. Just one thing, well maybe two. The Second Strike Pertronix has six wires. Black, Red, Yellow, White, Orange, and Green. Their diagram shows: Black to battery negative. Red to battery positive. Yellow is not used. White to tach output. Orange to original tach wire Green to original ignition switch wire At present the white wire is not hooked up. Pertronix: http://www.pertronix.com/support/manuals/pdf/second_strike%20.pdf Pertronix says "...relocate the tachometer trigger wire to the white wire from the Second Strike box" Do you have the second strike unit, Pertronix 500?
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| Posted: 08-11-2010 05:17 pm |
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8th Post |
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Gary Martin JH 15371 Member
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My Pertronix only has two wires. I don't have the second strike unit. I think you need to find someone that has installed the second strike unit on a JH. On a JH the ingition wire goes through the tach and on to the ballast resistor. There is no separate tach signal wire. Sorry I'm not more help. Gary
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| Posted: 08-11-2010 06:45 pm |
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9th Post |
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Greg Fletcher Administrator 
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There was an interesting tidbit in the newsletter a while ago- The cure is simple- you need to procure (2) 400V 3A diodes and place them in series (with the bands pointing in the correct direction). The diodes are fairly common and can be found at most electronic stores, or at Radio Slack stores under part# 276-1144.
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| Posted: 08-11-2010 07:06 pm |
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10th Post |
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timeforwalkies Member
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Thanks Greg. Place them in series where? Clif
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| Posted: 08-17-2010 12:49 am |
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11th Post |
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jdenglish Member
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Several years ago there was a shop in North Hollywood that would convert tachometers. It was featured in an article in the JHPS mag. I currently use a Pertronix and MSD unit to the converted tach. A long way around the problem but it works.
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| Posted: 08-17-2010 01:49 am |
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12th Post |
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Jensen Healey Super Moderator
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I use a 3 1/8" VDO tach that plugs in to the MSD. Accurate tach? What a concept! Kurt
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