Scarecrowtim

Hello, I am working on my brother-in-laws totally stock 240z. He was driving it a few months ago and the tach started pegging the gauge. It would only do it when it was hot outside. All of a sudden last week the tach just went to zero and so did all of the other gauges except the amp meter. He also lost the turn signals. We checked the fuses and all looked good and also removed the fuse block to make sure that there was no corrosion below the fuse block. It looked like new and there was no signs of corrosion.
Can anyone think of something that would cause this? Is there a common ground for all of the gauges? If so where might we find that.
Thanks for all of your help,
Take care and have a great day,

zxguy1986

Welcome to ZDriver!

Thanks for your post. If you know the actual year of your 240Z, you could tell that to the 240 pros here in your next post. If you don't know it, check out the factory service manuals you can download for free at XenonS30 and see if you can figure out which year you have there. Could be important. Also check out the troubleshooting and testing pages. Might be written in Early Japanese English - but you get the idea...

To post photos (always a good idea) sign in, click Post Reply, click on that little paper clip to the right of the smiley face at the top of the text space, locate your photos, click Upload, click Submit Reply, you’re done! If you show us the car you're asking about, it makes the pros get interested in your post - which is a good thing! Thanks again.

Scarecrowtim

I am sorry, it is a 72 240z,

Thanks

zxguy1986

Not a 240Z guy. If you check Section BE of your factory service manual, there are lots of good diagrams showing what connects to where. If you can decipher the detailed electrical diagrams (BE-4 and BE-5), you maybe could find the fault you're suspecting. It does sound to me like a harness-connection issue. Power isn't getting through the harness to the gauges - but the info they work off of (probably) is.

If you don't see a likely location for the fault in the FSM diagrams, may be time to disconnect, clean and reconnect every connector in the area. Connectors can get oxidized and grimy after 42 years!

Pez

Not a 240 guy either, but I did have to chase down a lot of these issues in my 76 280, and I agree with zxguy, with so much stuff not working it suggests that a harness is not doing it's job.

My issues were related to the two wiring harnesses on the left side of the passenger side floorboard. I was able to use a simple continuity test on my meter and figure out what wasnt working. It ended up being wires pulled out of the back of the harness connector... I bypassed this in two places and everything was good.

I didnt have any issues with the gauges.

Here's the link to the mother ******* turn signal thread.

https://www.zdriver.com/forums/240z-...t=turn+signals

beg3yrs

All the gauges that aren't working share a solid green wire which starts at the fuse block, goes through connector C-3 on the junction block and into the dash. It should be hot (+12V) when your ignition switch is on. The turn indicators share the same fuse and green wire as well.

Note: I have to admit I'm looking at a 260Z diagram but I don't think the basic circuitry differed all that much between the two models. If there's a major difference it is the location of the fuse block and the C-3 connector. The green wire is the key!

Scarecrowtim

Thanks for all of the great advice and I must admit the I feel rather stupid but wanted to post the solution in case someone else has the same problem. Previously I had checked both sides of the fuses to verify power and it did have it so I figured it had to be a problem somewhere else. I went back and looked at it again prepared to go to the next step whatever that may have been and checked it again with the circuit checker and there was no power coming out of the fuse box so I pulled that fuse and it had about 30-years of crud that prevented the power from getting thru. After cleaning the crud off everything now works and yes I do believe it was the green wire. Electrical problems so suck. Thanks for the help!

beg3yrs

Congratulations and don't even think about feeling stupid. We've all missed simple things like that and you had the guts to post the result. We learn from things like that. Thank you sir!

BTW, if there was 30 years of crud on that one fuse, the rest are likely to be just as dirty. Just sayin' ....

Pez

Nice! Easy fix. Hopefully this was before you tore a bunch of stuff apart

Scarecrowtim

Yes, I studied the wiring diagrams and was all physicked up and then I crawled under the dash and looked up. It was then that reality set in and I thought....Oh Crap!!!. Anyway, I then checked the grounds in the engine compartment and those checked out ok so I again went to the fuses and got lucky. Have I mentioned electrical problems suck. I am sure they are easy if you have the experience but that is not me, I guess I am just lucky. I should have went out and bought a lottery ticket

YZFMax

New to this site....

Apologies for bring this old thread up, but wanted to say thank you for your post! I had the exact same issue and did the same to trouble shoot. At the end, it ended up being the fuse area. Cleaned it up and the guages are now alive again.