Question on RPM gauge

gnsnprwldwsl · 05-12-2008, 07:14 AM

Does it get its reading from the igniter on the ignition coil ?

Or, as my friend said, does it get its reading from reading the
teeth on the flywheel ??

tymr287 · 05-12-2008, 08:53 PM

Tach gets its readings from the igniter.

gnsnprwldwsl · 05-13-2008, 04:35 AM

double post

gnsnprwldwsl · 05-13-2008, 04:35 AM

So if my car's RPM gauge isn't getting a signal, could the igniter be bad?

That can't be .. since I can drive the car just perfectly fine, right?

tymr287 · 05-13-2008, 08:35 PM

No, its not your igniter. If all the other gauges are working properly then there is probably an open in the wire from the igniter.

gnsnprwldwsl · 05-13-2008, 10:51 PM

Dang .. that would be a real hard thing to check for.

So open wire .. meaning the signal wire from the igniter has a
cut somewhere that severed the line...?

tymr287 · 05-13-2008, 11:13 PM

Yeah, but you might not see the break if the insulator around the wire is not broke/damaged. Get an ohm meter and check continuty from the ignitor to the tach. If you don't get a reading, trace the wire back to the igniter, stopping every now and then checking for continuty.

tjmr2 · 05-14-2008, 12:56 AM

For an 89 the Tach gets it's signal from the igniter, pin 4, a black wire, it stays a black wire all the way to the tach.

The tach has 3 wires connected to it, A red with blue stripe hot +12v wire, a white with black stripe - ground and the black signal wire from the igniter.

Hope this helps

gnsnprwldwsl · 05-14-2008, 04:09 PM

The signal wire coming from the igniter, does it run straight from the igniter and runs all the way to the tachometer??

When i was checking on my '85, I saw that the wire runs back into the big harness wrapper and appeared to go to the ECU. So I saw that and wasn't sure how to check the wires.

So ohm-meter and poke into the wires to check for continuity every little bit or so ??

tjmr2 · 05-16-2008, 01:25 AM

Without the BGB it can look confusing. I speak only for the 89 as that's the BGB I have.

3/4ths of the wires from the igniter do indeed go to the ECU, quite possibly bundled with the two wires from the distributor. One of the wires from the ignitor - pin 4, the only black one that leaves the igniter does go to the tachmometer. Use a long test lead on your ohm meter and test it to the black wire going to the tach. Remember you have to disconnect one end of a wire before you check it or you read the wire and possibly the circuit behind it.

Good luck

DCKilla · 05-21-2008, 10:36 AM

If your multimeter shows that the wire is open. Start looking for breaks in the wire close to the connector. This is where most breaks happen. If the connector, pin, and wire look good check holes, clamps, and zip-ties along the wire. Also check where the wire bends sharply. These things are not hard to find. Good luck!

05-12-2008, 07:14 AM	#1 (permalink)
gnsnprwldwsl Cage Fighter Join Date: Jan 2008 Location: Los Angeles Posts: 109 Thanks: 4 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	Question on RPM gauge Does it get its reading from the igniter on the ignition coil ? Or, as my friend said, does it get its reading from reading the teeth on the flywheel ??

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

05-12-2008, 08:53 PM	#2 (permalink)
tymr287 Some Skills Join Date: Jan 2008 Location: New Orleans Posts: 74 Thanks: 0 Thanked 7 Times in 5 Posts iTrader Rating: (0/0% )	Tach gets its readings from the igniter.

05-13-2008, 04:35 AM	#3 (permalink)
gnsnprwldwsl Cage Fighter Join Date: Jan 2008 Location: Los Angeles Posts: 109 Thanks: 4 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	double post

05-13-2008, 04:35 AM	#4 (permalink)
gnsnprwldwsl Cage Fighter Join Date: Jan 2008 Location: Los Angeles Posts: 109 Thanks: 4 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	So if my car's RPM gauge isn't getting a signal, could the igniter be bad? That can't be .. since I can drive the car just perfectly fine, right?

05-13-2008, 08:35 PM	#5 (permalink)
tymr287 Some Skills Join Date: Jan 2008 Location: New Orleans Posts: 74 Thanks: 0 Thanked 7 Times in 5 Posts iTrader Rating: (0/0% )	No, its not your igniter. If all the other gauges are working properly then there is probably an open in the wire from the igniter.

05-13-2008, 10:51 PM	#6 (permalink)
gnsnprwldwsl Cage Fighter Join Date: Jan 2008 Location: Los Angeles Posts: 109 Thanks: 4 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	Dang .. that would be a real hard thing to check for. So open wire .. meaning the signal wire from the igniter has a cut somewhere that severed the line...?

05-13-2008, 11:13 PM	#7 (permalink)
tymr287 Some Skills Join Date: Jan 2008 Location: New Orleans Posts: 74 Thanks: 0 Thanked 7 Times in 5 Posts iTrader Rating: (0/0% )	Yeah, but you might not see the break if the insulator around the wire is not broke/damaged. Get an ohm meter and check continuty from the ignitor to the tach. If you don't get a reading, trace the wire back to the igniter, stopping every now and then checking for continuty.

05-14-2008, 12:56 AM	#8 (permalink)
tjmr2 Cage Fighter Join Date: Jan 2008 Location: Colorado Posts: 410 Thanks: 0 Thanked 62 Times in 59 Posts My Google Map iTrader Rating: (0/0% )	For an 89 the Tach gets it's signal from the igniter, pin 4, a black wire, it stays a black wire all the way to the tach. The tach has 3 wires connected to it, A red with blue stripe hot +12v wire, a white with black stripe - ground and the black signal wire from the igniter. Hope this helps

05-14-2008, 04:09 PM	#9 (permalink)
gnsnprwldwsl Cage Fighter Join Date: Jan 2008 Location: Los Angeles Posts: 109 Thanks: 4 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	The signal wire coming from the igniter, does it run straight from the igniter and runs all the way to the tachometer?? When i was checking on my '85, I saw that the wire runs back into the big harness wrapper and appeared to go to the ECU. So I saw that and wasn't sure how to check the wires. So ohm-meter and poke into the wires to check for continuity every little bit or so ??

05-16-2008, 01:25 AM	#10 (permalink)
tjmr2 Cage Fighter Join Date: Jan 2008 Location: Colorado Posts: 410 Thanks: 0 Thanked 62 Times in 59 Posts My Google Map iTrader Rating: (0/0% )	Without the BGB it can look confusing. I speak only for the 89 as that's the BGB I have. 3/4ths of the wires from the igniter do indeed go to the ECU, quite possibly bundled with the two wires from the distributor. One of the wires from the ignitor - pin 4, the only black one that leaves the igniter does go to the tachmometer. Use a long test lead on your ohm meter and test it to the black wire going to the tach. Remember you have to disconnect one end of a wire before you check it or you read the wire and possibly the circuit behind it. Good luck

05-21-2008, 10:36 AM	#11 (permalink)
DCKilla Cage Fighter Join Date: May 2008 Location: Pearl, MS Posts: 153 Thanks: 1 Thanked 6 Times in 6 Posts iTrader Rating: (0/0% )	If your multimeter shows that the wire is open. Start looking for breaks in the wire close to the connector. This is where most breaks happen. If the connector, pin, and wire look good check holes, clamps, and zip-ties along the wire. Also check where the wire bends sharply. These things are not hard to find. Good luck!