hi i just bought a half sweep repop moon tach and it seems to be registering low i had a super rach teo in it before and i shifted at 5,200 but now the moon reads 4,200 at the same speed the lower rpms seem to be just finemaybe a hundred off, like idle and cruisingis fine and such but it gets off by alot on high r's , has anyone had this issue before ? im pretty bumded this has been one of the things ive allways wanted since i was,a little kid , any helps appreciated thanks Posted using the Full Custom H.A.M.B. App!
I have the same problem with mine.At idol mine reads 100 rpm's.When im cruzing on the free way at 65 mph it reads 4300 rpms.The car it is in is a 66 el camino with three on the tree and 373 rear gears.No way thats right.Im thinking it runs around 3000 rpm's at that speed.I run an hei distributer in a chevy small block.Yes the selector is on 8 cylinder position.I have tried all positions.I called moon they said send it back so i did and they sent me new one.Same thing with the new one.
Do a search on moon tach or moon eyes tach ..... other threads on here (including an old one from me ) about these tachs. Made in a shitty factory below a big brick wall.... .
Wired mine in last Friday, shows idle at 300 RPM's. Drove it down the road 4 miles and think it somehow took out the Petronic's unit in the distributor. Made it home but was on about 4 cylinder's. Everything is wired correct, 4 wire set-up and tach is set for 8 clyd. Not real happy ! Oops ended up being a carb issue, tach is still way on the low side.
I had one for a few months, then it started working erratic. I replaced it with a Retro Autometer. I was shocked at how much heavier the Autometer one was in comparison to the Moon tach.
Also have the Autometer Retro in my truck. Works great so far! Posted using the Full Custom H.A.M.B. App!
They were going for a look, and had them built cheaply off shore. Better to buy another modern tach and fit it into the old Moon repop housing if you want to have a working tach. Or mount another good tach out of sight and just disconnect the Moon if you like the look.
Hate to bump such an old thread, but I am having the same issue. Worked fine a few months ago when I installed it, now it doesn’t “sweep” smoothly – very erratic and it certainly doesn’t read correctly. When I got it, I was disappointed. Off shore made junk.
Sounds like it is still a problem judging by this thread a few months ago https://www.jalopyjournal.com/forum/threads/moon-tach-no-rpm-reading.1330440/#post-15496049 I bought an old Dixco half sweep after hearing of the issues with the Moon ones, but the Dixco also seems to read a little low when tested it out with the SBC in my truck. It was pretty shabbily hooked up with some alligator clips just to test it so that could have contributed to it, but im gearing up to have to replace it when it goes in the car i bought it for
The Moon half sweep techs are trouble. I had one in my 53 Chevy (261 6 Cylinder) it quit in a relatively short period of time. Moon replaced it but the second one quite before the end of that summer. There have been several threads regarding people’s troubles with them.
After reading all this, emptying my piggy bank to get an NOS Sun tachometer doesn't seem so bad. You can buy an old scratched up Sun tachometer that might not even work for not very much money. Have Bob's Speedometers or others fix it. Clean it up, paint it up, buy a new cup and mounting bracket and an inexpensive modern electronic sender and you're good to go. And it'll work. This is mine. Ok, maybe I'm showing off a little. But can you blame me?
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