hpltree Posted February 4, 2009 Share Posted February 4, 2009 Ok here we go , i have been searching for a few months but with no answers that have helped.. I have a 73 240 pretty much stock and the tach just pegs when i turn the key on. I have spent many hours cleaning grounds and checking all the connecters but nothing has helped. Is the tach just no good or have i missed something? It has no after market ignition parts. Thanks for the help Quote Link to comment Share on other sites More sharing options...
jasper Posted February 4, 2009 Share Posted February 4, 2009 Did you check inputs to the tach, with a multi meter and wiring diagram? Otherwise....It's just a guess as to the cause. Quote Link to comment Share on other sites More sharing options...
hpltree Posted February 4, 2009 Author Share Posted February 4, 2009 No i have not. i was going to pull the tach out of the dash but was turning into a pain, but if that is what needs to be done i will do it. Do you know what the inputs should read or how i can get that info? I have been chasing the diagrahm for weeks Quote Link to comment Share on other sites More sharing options...
jasper Posted February 4, 2009 Share Posted February 4, 2009 I just checked a factory manual. A VERY small, and difficult to read wiring diagram. MAYBE a Haynes is better, or you may want to do a search. Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted February 4, 2009 Share Posted February 4, 2009 My 260 tach did that when i first got my car. It turned out to just be a bad tach. Quote Link to comment Share on other sites More sharing options...
hpltree Posted February 4, 2009 Author Share Posted February 4, 2009 Thanks jasper for the help , i have been searching on this site for a few months, i didnt want to get in trouble from the higher ups... i have been using the Haynes book to do the wire chasing, also printed off a copy of the auto zone diagram . I am thinking i am just missing something easy. But i am new to this car so im not sure. I know the tach triggers off of the positive side of the coil unlike most cars. thanks again for any help Quote Link to comment Share on other sites More sharing options...
hpltree Posted February 4, 2009 Author Share Posted February 4, 2009 Ok just a bad tach. That would make sence, is there a way that i could test it? thanks 949 Quote Link to comment Share on other sites More sharing options...
ArizonaZ Posted February 4, 2009 Share Posted February 4, 2009 I have the same problem in my 260, when I turn the key it will go to redline, and I think that only thing thats stopping it is the pin, but sometimes it will back off of the needle and settle at 7000 and then sometimes it does nothing, so im pretty sure that its just a bad tach Quote Link to comment Share on other sites More sharing options...
hpltree Posted February 5, 2009 Author Share Posted February 5, 2009 yep mine will back off a little to about the 7 grad mark when the battery gets a bit weak. today i fixed the temp guage and was slapping the gas peddle a few times and when i shut it off the tach stuck on the peg for a second or two. Its becoming entertaining.. thanks for the help Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted February 6, 2009 Share Posted February 6, 2009 Most of the time, that kind of tach behavior means you have a body ground issue.........in most every other car......maybe not in yours, though. It doesn't cost anything to connect a pair of jumper cables between a strut bolt and the engine to see if the problem goes away. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted February 6, 2009 Share Posted February 6, 2009 It's most likely the tach. I was adjusting mine and was too lazy to turn the engine off and killed it the same way. Luckily I had a spare. I may try to rebuild the bad tach and if I succeed, I'll post how I did it. Note: I thought I remembered a writeup somewhere (not on hybridz) on how to rebuild it, but can't find it now. I'm attaching the schematic. I think the issue will be finding replacement transistors. Quote Link to comment Share on other sites More sharing options...
hpltree Posted February 7, 2009 Author Share Posted February 7, 2009 thanks for the input guys ill try the cable idea Quote Link to comment Share on other sites More sharing options...
Sean 71 Posted October 10, 2009 Share Posted October 10, 2009 I was wondering if you found out what the reason was for the tach pegging out? I have a 73 that just started doing the same thing, only it would do it for a day, then the next day it would read fine. It seems to be more and more sitting on the red line as the days go by. Quote Link to comment Share on other sites More sharing options...
hpltree Posted October 13, 2009 Author Share Posted October 13, 2009 well i never did find the cause, i just figured it was blown up after playing with it for way to long.. i found 2 280 tachs in my local pick a part and put one in. the face plate is just a bit different looking but it works great. sorry i dont have the easy fix answer. on a good note i just ordered my JTR conversion manuel and cant wait to get it, ill get some pictures and keep everyone up to date Quote Link to comment Share on other sites More sharing options...
Sean 71 Posted October 15, 2009 Share Posted October 15, 2009 Ok. Good to know. Quote Link to comment Share on other sites More sharing options...
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