240260280z Posted May 16, 2014 Share #13 Posted May 16, 2014 check your condensers. They can fail intermittently with heat and some may be in the tach circuit. Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-447928 Share on other sites More sharing options...
rcb280z Posted May 16, 2014 Author Share #14 Posted May 16, 2014 How many condensers are there? There is the one for the alternator and that is the only one I can think of at the moment without digging thru the manual. Which I do not feel like doing after the day I've had. I know, no excuse Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-447932 Share on other sites More sharing options...
Zed Head Posted May 16, 2014 Share #15 Posted May 16, 2014 (edited) My original tach would "hang high" when it got hot in the car. 1976 280Z. Mid-summer, after a long drive, it just wouldn't come back down, it hung at around 2500 RPM, I think. After everything cooled, it went back to to normal. I got tired of it and swapped a 1978 tach in.I don't really understand how these tachs work, so couldn't even guess on a cause. Edited May 16, 2014 by Zed Head Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-447937 Share on other sites More sharing options...
Mikes Z car Posted May 16, 2014 Share #16 Posted May 16, 2014 There might be a transistor amplifier that drives the tach needle that might not be well stabilized against temperature variations. All I know about that is that one way for the designer to temperature stabilize a transistor amplifier is to put a resistor in series with the emitter of the transistor and ground. Maybe the designer selected the wrong resistor value or the resistor has changed in value with time, I have seen them change in old radio equipment. I wouldn't know what else to guess though. Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-447938 Share on other sites More sharing options...
EuroDat Posted May 16, 2014 Share #17 Posted May 16, 2014 How many condensers are there? There is the one for the alternator and that is the only one I can think of at the moment without digging thru the manual. Which I do not feel like doing after the day I've had. I know, no excuse I can think of three, just from memory. The one on the alternator. Another is located near the voltage regulator, A/C relay under the metal bracket the fusable links are mounted on. The third is mounted on the coil and has two wires coming out of it. I have seen a thread here from a member in Italy and he thought it had 6 or 7, but I can't find the thread right now. There could be more under the dash, need to dig through the manual to find out. Chase Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-447941 Share on other sites More sharing options...
rcb280z Posted May 20, 2014 Author Share #18 Posted May 20, 2014 Okay, I have no idea what is going on. Unless it is heat related but the Tach is working fine! It is about 18 degrees cooler around here. Guess I'll have to wait til it gets hot again to trouble shoot it. Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-448147 Share on other sites More sharing options...
Captain Obvious Posted May 22, 2014 Share #19 Posted May 22, 2014 Glad that it's working, but you know the problem will come back, right?Were you able to determine if it's a mechanical "needle sticking" or if it's an electrical problem? Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-448268 Share on other sites More sharing options...
rcb280z Posted May 22, 2014 Author Share #20 Posted May 22, 2014 Im going to say electrical. Each time I raised the rpms the needle would sometimes raise accordingly and then stick. When I came to a complete stop I could tap on the face of the tach and the needle would sometimes drop. Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-448269 Share on other sites More sharing options...
rcb280z Posted May 22, 2014 Author Share #21 Posted May 22, 2014 Oh...yes I know it will come back. I dont have any time to work on her right now. But when I do I will post what I find. Link to comment https://www.classiczcars.com/topic/49227-swell/?page=2#findComment-448270 Share on other sites More sharing options...
Wilbur
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