Hi guys I have a question about my TACHO in my SS HATCH 308. I have read on here about the tacho needing modification when running HEI ignitions. My tacho seems to work fairly normally when cold but when the motor is hot it goes crazy. At idle when hot it can read at 5000 to 6000 rpm and when you accelerate it will drop down lower.So in other words it is working in reverse. I have my instrument cluster out of the car and taken to an instrument repairer.The repairer says he can't find anything wrong with it and says it is working perfectly under his testing.He says he thinks that it is the coil starting to breakdown when hot and is interfering with the tacho.Does this sound right to you guys and if so what sort of coil should I get.If this sounds wrong any recommendations where I should try next in Brisbane or the Sunshine Coast. Thanks for any help you can give DALE
LX Tacho
#1
Posted 09 July 2018 - 05:53 PM
#2
Posted 09 July 2018 - 06:56 PM
Or try,
Lionel Otto Instruments - Salisbury, Brisbane
#3
Posted 09 July 2018 - 10:13 PM
I've had this in the past on a Sigma with the bosch module just before it died.
#4
Posted 10 July 2018 - 06:24 PM
RODOMO what do you mean by bosch module
#5
Posted 10 July 2018 - 07:04 PM
#6
Posted 10 July 2018 - 09:50 PM
This is common with a module on its way out. On the Bosch HEI distributors, it's under the metal cover hanging off the side. if you change it yourself, two screws and be gentle prying the connectors off. Really can't go wrong. Just make sure the ignition (usually pink) goes back on the terminal marked 15. And don't forget to put some heat sink paste on the bottom
Also might be a good time to check the pick up coil as well (the two skinnier black wires). If i recall, a resistance of 750-1150ohms is the range. ANY over or under i would bin it instantly.
#7
Posted 11 July 2018 - 12:20 AM
The BIM024 (BIM means Bosch Ignition Module) was common to a lot of cars back in the 80's. Scroll through these e-bay listings and you'll see what I mean: https://www.ebay.com...ignition module I've also had cars that wouldn't start on the roadside and by merely loosening, then retightening the module cover screws away they have gone.RODOMO what do you mean by bosch module
#8
Posted 11 July 2018 - 07:03 PM
Thank you for that information I will certainly look into that DALE
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