Tach and Blinker

Cal44

Cal44

Gold forum user
Messages
428
No...........it's not a law firm.

Yesterday I took the Tig out for a little spin. I had just finished "fixing?" the return on the blinker assembly.

I was so proud of myself, until I tuned on the blinker to make a turn.
I happen to look down at the tach and each time the blinker would blink the tach would go from 900 rpm to 200 rpm and then pop back up too 900.

It would have been funny.............if it was someone else's car.

Got any ideas?
 
The mystery of magnetism

In electro physics, it's called induction. A malady more common in DC current, although will heat up the circuit breakers in an AC system if you seperate the wires for any distance. Try an individual wire path that will get it away from the same harness source feeding the flasher unit. Or, find a metal shielded unit instead of the new plastic junk.
 
While I may respectfully disagree with Randy's fundamentals explanation, I do agree with his conclusion.

Randy gave you the short version. At risk of adding confusion instead of understanding, here is a little additional explanation that may help in inplementing the solution.

Are you running a stock tach? Sometimes they will work with a Pertronix ignition, some times not. Anyway the stock tach has an induction (there is that word again) pickup. There is a white, insulated wire wrapped around a post at the back of the tach. That is the power wire to the coil. As the ignition fires, there are electrical pulses that reflect back up the wire to the tach (as an AC signal of sorts). The faster the pulses, the more energy that is coupled by induction into the tach and the faster it reads. the tach basically is a counter and the more counts per minute, the higher the meter reads.

Your flasher also generates pulses of electricity to the turn signal lights. It could well be the wires to or from the flasher are close to the tach pickup or the wire that is part of the pickup. If so, those pulses could be picked up and by induction (so-called cross talk) into wires that make up the tach pickup circuit. The combination of ignition and those blinker pulses would generate a net slower pulse, causing the tach reading to drop. Afterall the lights blink slower than the engine fires.

It could also be that the flasher is not properly shielded, radiating energy pulses that are being picked up by the tach. It is mounted fairly close to the tach. So, you might also try a different flasher unit.

Hope there is some help and additional understanding in all of that. My apologies if all of that is stuff you already know.

Test next Monday, open book, including chapter on inductive reasoning.:D

Cheers, Gene
 
Synapse re-alignments

Le Quote: "While I may respectfully disagree with Randy's fundamentals explanation, I do agree with his conclusion."

Gene: Fun-de'-mentals are lost in the logic of inductive reasoning. I could spout about the years spent teaching over educated industrial "experts" on the art of avoiding magnetic induction booby traps on both AC & DC systems, but the barnyard short versions get it all done without fanfare (or coat & tie). A field expediant "Kick it here" is easy to fathom. Re-test on Tuesday . . . . . .
 
Thanks guys.

Stated from two different angles but ending at the same point.

This reminds me of changing out my speedo cable where the needle bounced around like a kid with ADD.

I put in a new cable..........then it didn't work at all............

quacks me up........
 
I recommend an Autometer 8000 RPM Cobra tach with a Tiger face and needle. No messing up a modern tach.

012-1.jpg
 
Randy, there is no substitute for real experience. Very much in agreement with that. But, I guess I am just one of those people you must consider an overeducated type. Although I do not think education is ever a bad thing. Some people may want to know the why as well as the how.

Gene
 
michael-king said:
Duke... you have negative rpm!
Click to expand...

Yea...yea... that's where it likes to hang out when not running. I get great gas mileage though.

OBTW - the custom display board is ready at the printer, I'll get it tomorrow. Just in time for the Midwest Ford Fest on Saturday. I hope to smoke some Cobras in the 1/4 mile.
 
Duke Mk1a said:
Yea...yea... that's where it likes to hang out when not running. I get great gas mileage though.

OBTW - the custom display board is ready at the printer, I'll get it tomorrow. Just in time for the Midwest Ford Fest on Saturday. I hope to smoke some Cobras in the 1/4 mile.
Click to expand...

You could get a parts gauge, even a fuel or temp one and take the little needle stop off and put it on your sneaky tach, give the needle soemthing to rest on.

As for the display board, hope it prints out nicely, look forward to seeing the pics.. and hearing how you did in the 1/4's
 
TigerBlue said:
Try to remember not to use your turn signal when racing :D
Click to expand...

So... if the turn signal's on... does that give you an 8 grand tach using your stock tach...?? ;-)

Duke: Glad to see you're still liking your tach.. I've sent out several of them now... no complaints... Hey, I have one left with a 7k redline face if you're feeling up to it... ;)

Jim
B382000446
 
michael-king said:
You could get a parts gauge, even a fuel or temp one and take the little needle stop off and put it on your sneaky tach, give the needle soemthing to rest on.

As for the display board, hope it prints out nicely, look forward to seeing the pics.. and hearing how you did in the 1/4's
Click to expand...

Nahhh...It does not bother me. Well, the 1/4 mile calculators say that with my cars weight and HP, it can run a 11.12 second 1/4. Now lets see if I can get it to hook up and if I can even drive the thing with some skill. The nut behind the wheel may really slow the car. If I can crack 12, I will be a VERY happy guy!

66TigerMK1A said:
Duke: Glad to see you're still liking your tach.. I've sent out several of them now... no complaints...
Click to expand...

The tach is fantastic. An absolute requirement for the 347. I have a MSD pro-billet ready to run distributor with a built in rev limiter. When I turn on the ignition, the tach jumps to the rev limit and then back to 0. It is real neat as I can see that it is calibrated correctly before I start the engine each time. Only problem I have with the tach is that in 4th gear it will very quickly go to redline under full throttle.

My speedo does not work and I have no plans to fix it. I use a GPS for long trips.
 
Duke Mk1a said:
Only problem I have with the tach is that in 4th gear it will very quickly go to redline under full throttle.

My speedo does not work and I have no plans to fix it. I use a GPS for long trips.
Click to expand...


That's why I suggested the 7k redline ! lol!!!

Ditti on the speedo... I finally figured out that when my speedo is jumping from 40-60... I'm doing 40 ... and when it's jumping 60-80, I'm doing 60... lol I have the tach calibration in my head now... 60 mph is 2100 rpm in 5th... etc.

Jim
 
66TigerMK1A said:
That's why I suggested the 7k redline ! lol!!!

Ditti on the speedo...... 60 mph is 2100 rpm in 5th... etc.

Jim
Click to expand...

I don't feel good pushing the 347 to 7K. I have it a 6200 right now and may move it to 6500 in the future. Max HP is at 5800 so it is all down hill above that anyway.

5th! I only wish. Thinking about a 2.72 rear end. Have a 3.07 now.


SORRY FOR THE THREAD HIJACK
 
Just a quick follow up. It was the bundle of ground wires............not grounded in the middle area of the dash. Where the knee pad attaches to the metal.

As a buddy always tells me........."it's usually a ground when things don't work correctly"

Mike
 
You must log in or register to reply here.
Back
Top