I had a aftermarket tach professionally installed (auto gauge). Worked fine all day long then all the sudden it started idling at 2,000 rpms instead of right below 1,000. My regular take is still workin fine, however the guy I bought it off said usually with these tachs if there defective the dont work at all. I was wondering what yall thought, could it be faulty installation or faulty tach?

Thanks

 

maybe its a bad ground or loose wire? sorry im not sure how aftermarket tachs are hooked up