Factory Tachometer Keeps Sticking
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Cargo Master
Joined: Dec 2004
Posts: 3,362
Likes: 22
From: Florence, SC
Factory Tachometer Keeps Sticking
The factory tachometer on my 1985 F150 keeps sticking. Sometimes, especially when it is cold, the tach doesn't move for about the first 15 minutes. Then, when it does decide to get off the bottom of the gauge, it will slowly rise to the highest rpm I ran so far that day and then it will stay there for a while. Then, if I am lucky, it will decide to start working. On shorter trips the needle never gets loose enough to catch up, and it will remain stuck at the highest rpm I ran that day, even when I shut the truck off. The next day, it is always at the bottom of the gauge again.
What is causing this, and how do I make it work right again?
What is causing this, and how do I make it work right again?
Cargo Master
Joined: Mar 2007
Posts: 2,935
Likes: 34
From: Arcadia, Fla
Sounds like that old yellow turning brown glue Ford used in the tachometer ckt pc board to keep parts from moving. There's a thread about this problem, which can't find right now....
Pull the tach from the cluster and look on the circut board of the tach, you probly will find some yellow glue thats turning brown and causing all kinds of wierd tach readings. Pick off ALL that yellow and browning glue and clean off that pc board. Be carefull not to dammage resistors and caps mounted on the ckt board. That probly will fix it for you.
What is happening is that yellow glue is turning conductive when it browns up.
Pull the tach from the cluster and look on the circut board of the tach, you probly will find some yellow glue thats turning brown and causing all kinds of wierd tach readings. Pick off ALL that yellow and browning glue and clean off that pc board. Be carefull not to dammage resistors and caps mounted on the ckt board. That probly will fix it for you.
What is happening is that yellow glue is turning conductive when it browns up.
Junior User
Joined: Feb 2007
Posts: 85
Likes: 0
i seem to be having the exact opposite problem with the tach in my truck. i have a 4.9 and it says its idling at 1200rpms and is pegged past 6000rpm going down the road. the truck sat idle for about 6 month and it started this as soon as i got it back out...possibly to do with some crud in the tach also?
Elder User
Joined: Jan 2009
Posts: 712
Likes: 0
From: Blue Eye, mo. hwy 86 & JJ
well pullin the cluster then the tach from the cluster isnt that bad, so it would be the first thing i'd check....
FYI: i have a 80-86 automatic cluster, no tach, with all instruments working. anyone who wants it make me an offer
FYI: i have a 80-86 automatic cluster, no tach, with all instruments working. anyone who wants it make me an offer
Cargo Master
Joined: Mar 2007
Posts: 2,935
Likes: 34
From: Arcadia, Fla
Ford-harto3457 ,it could very well be same problem for you too. That crap causes all kinds of problems when it breaks down and turns into "resistors". Depending on where is conducting I have seen my tach bounce all over the place and another was always 2K and above, a 3rd was dead with no movement. All 3 were fixed by removing that glue and cleaning off the pc board.
Cant hurt to try it.
Cant hurt to try it.
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