Factory tach install question
Posting Guru
Joined: Aug 2009
Posts: 2,271
Likes: 2
From: Mexia, TX
Cool. I like the short-jumper idea, it'll save on wire and won't make the rat's-nest of wires under my dash any worse. lol.
I'll see what happens when I add this jumper and then I'll check back with the results.
I'll see what happens when I add this jumper and then I'll check back with the results.
Posting Guru
Joined: Aug 2009
Posts: 2,271
Likes: 2
From: Mexia, TX
Jumper is in place, and I don't notice much difference. It's spot-on at some speeds and a tiny bit off at others. But then again, it's a 25-30 year old tach, so can I really expect it to be as accurate as one that's only a few years old?
Cargo Master
Joined: Mar 2007
Posts: 2,935
Likes: 34
From: Arcadia, Fla
Is the tach bouncing around sometimes? The few 82 to 86 tachs I messed with had glue inside the tach that turns brown and causes all kinds of readings. In the the tech section there's a link about how to clean it up. https://www.ford-trucks.com/forums/7...dywhompus.html
As a side note, a few years ago(15 or so.??) I read up on a magizne about tachometers being accurite. They are NOT some of the times. The mag hooked up several tachs to one engine and showed they differed on average 100 to 300 RPM! The "only accurite" tach was a computer set up that measured RPM in the microseconds range.
As a side note, a few years ago(15 or so.??) I read up on a magizne about tachometers being accurite. They are NOT some of the times. The mag hooked up several tachs to one engine and showed they differed on average 100 to 300 RPM! The "only accurite" tach was a computer set up that measured RPM in the microseconds range.
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Posting Guru
Joined: Aug 2009
Posts: 2,271
Likes: 2
From: Mexia, TX
It does seem to move just a tiny bit at sustained RPMs (doesn't matter what), but it's not bouncing. It moves maybe a millimeter or two, that's it. I do want to do like you did and clean off that glue, though. Doesn't it require disassembling the tach itself?
Well that would explain alot. I suppose it could be at least partially due to design differences.
Well that would explain alot. I suppose it could be at least partially due to design differences.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
The insides of a tach are delicate (these are semi-precise instruments). If you open yours up
(not real hard, I think all you hafta do is remove the 4 nuts) be careful with the insides.
(not real hard, I think all you hafta do is remove the 4 nuts) be careful with the insides.
Cargo Master
Joined: Mar 2007
Posts: 2,935
Likes: 34
From: Arcadia, Fla
The real worry is not to mess up the needle, dammage it and the tach is junk. The way these tachs come apart there is no need to mess with the needle at all. The pc board inside are pretty rugged as long as you don't over "pick" the brown/yellow glue out.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
delicate assemblies; the PCB is pretty rugged.
Posting Guru
Joined: Aug 2009
Posts: 2,271
Likes: 2
From: Mexia, TX
I learned about that years ago...I was like 15 and I had removed the speedometer from a parts truck my dad and I bought....stupid me, I messed with the needle and ruined it. Those springs are like a slinky, kink it once and you're out of luck. lol
I got to thinking about it, and the tach seems to be working perfectly so far. I think I'll go ahead and leave it alone and not disassemble it. If it acts up later on, I'll clean off that glue.
Haven't gotten around to testing the circuit film for more breaks yet. I have noticed that my gas gauge is at least somewhat accurate. I think it gets flaky when I get close to empty. I'm guessing the sending unit might be to blame, since the gauge reads perfectly from about 1/4 tank up.
I got to thinking about it, and the tach seems to be working perfectly so far. I think I'll go ahead and leave it alone and not disassemble it. If it acts up later on, I'll clean off that glue.
Haven't gotten around to testing the circuit film for more breaks yet. I have noticed that my gas gauge is at least somewhat accurate. I think it gets flaky when I get close to empty. I'm guessing the sending unit might be to blame, since the gauge reads perfectly from about 1/4 tank up.
Posting Guru
Joined: Aug 2009
Posts: 2,271
Likes: 2
From: Mexia, TX
Indeed. Got some experts here! 
That's exactly what I thought. Plus I've removed the gauges like four times since I installed them, so I'm kinda getting tired of doing it over and over again...lol
That's exactly what I thought. Plus I've removed the gauges like four times since I installed them, so I'm kinda getting tired of doing it over and over again...lol