Tachometer issues...

SFaikel · #1 (**permalink**) 04-28-2008, 08:35 PM

Hello, I have an '87 Spider and starting late last year I noticed that when starting it up in the morning or after rain, etc. the tachometer wouldn't work until the engine had heated up a bit, but it ws usually fine after the first mile or two. After taking it out this spring it has gotten much worse and it doesnt work until the engine has hit 175 degres. I was wondering if anyone could help me trouble shoot it. I've been wanting to adjust it so that it's more accurate but throught I should take care of this first. Thank you so much!

Oski_Bear · #2 (**permalink**) 04-28-2008, 09:33 PM

Spencer, my 88 spider has also started to have erratic tach behavior. Sometimes its sluggish and won't go above 2000 RPM. Other days it's perfectly fine. I haven't figure out if its temperature related though.

SFaikel · #3 (**permalink**) 04-29-2008, 10:06 AM

Yes, it defiantly gets better after it's warmed up, don’t know if it's because of temperature or timing or what.... Mine seems to be fairly accurate until you get to 3000 rpm. Then it doesn’t want to go much higher, reading about 3500 when I'm sure I've reached 5000...

Oski_Bear · #4 (**permalink**) 04-29-2008, 11:02 AM

Yeah...dito. I generally use my ear as a tach now and I probably don't go over 5000 RPM.

SFaikel · #5 (**permalink**) 04-29-2008, 06:39 PM

Well, today after work it would turn on and off and then back on again so I'm guessing it's electrical.... Any suggestions?

SFaikel · #6 (**permalink**) 04-30-2008, 12:41 PM

come now, I know someone has some idea!

Oski_Bear · #7 (**permalink**) 04-30-2008, 12:44 PM

Have you read the threads on removing the instrument cluster? I think we both might have a dirty/loose connection back there to the tach. The other possibility is a loose/dirty connection in the line that feeds into the instrument cluster. I've done reading on the forum but haven't been able to find out where the signal comes from.

**papajam** · #8 (**permalink**) 04-30-2008, 01:54 PM

The signal comes from terminal #1 (negative side) of the ignition coil. There are a number of wires there one of which is a white wire for the tach signal.

SFaikel · #9 (**permalink**) 04-30-2008, 02:49 PM

Quote:

Originally Posted by Oski_Bear

Have you read the threads on removing the instrument cluster? I think we both might have a dirty/loose connection back there to the tach. The other possibility is a loose/dirty connection in the line that feeds into the instrument cluster. I've done reading on the forum but haven't been able to find out where the signal comes from.

**papajam** · #10 (**permalink**) 04-30-2008, 05:58 PM

Quote:

Originally Posted by SFaikel

So then would I be correct in saying that my signal comes from thge coil, not a flywheel sensor?

SFaikel · #11 (**permalink**) 04-30-2008, 08:15 PM

Sounds swell! Thank you very much for that! Alright... new news... On the way home today the tch wasn't working so I decided to "smack" it as suggested in this thread and wouldnt you know, it came to life! So I'm guessing it is the electrical connections on th bck of the gauge. Thank you all so much for your help!