Tach oscillates when indicator is on (Page 1/2)
ReptilianRascal OCT 06, 01:07 AM
Hi all.

New owner of an 88GT and new member of the forum here (first post).

I'm currently getting it ready for registration and I'm slowly working through all the niggling little problems I've found in the last few months since purchasing.

The main one I'm concerned might be a sign of something worse about to rear its head is the tach needle oscillates while the indicator is on. The volt meter needle does the same.

The battery is new and this happens when both at idle and while reving.

To give it more of a description, the tach and volt meter needles are steady when the indicator is off. When I switch it on (either left or right - happens the same with both sides), the needles start dropping and then coming back up to normal in time with the indicator light turning on and off respectively. The volt meter goes down to maybe 9V from the 13V when the indicator is off and the tach drops by about 600-800rpm when it's flashing on then back to normal when the light if off (I hope that description makes sense).

I'm wondering if this might be the tach filter that needs replacement (on the list of things to do anyway) or if it could be anything else.

Any help or suggestions would be appreciated.

Cheers
RR

Ps. Please let me know if this has been discussed anywhere else. I tried searching the forum for this but nothing I found was exactly the same situation.
theogre OCT 06, 01:54 AM
volt meter etc bumps w/ turn lights On is covered here many times...

In short...
Have iffy grounds anywhere in the car.
Have iffy connectors etc for 12v side.
Have weak alt and/or "power pulley" crap causing weak alt output.

See my Cave, Wire Service and other cave pages.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

ReptilianRascal OCT 06, 04:16 AM
Thanks for that. That's really helpful.

I think it might be the ground behind the radio as there has definitely been some work done there by previous owners and there were some other loose fittings in that area.

Really appreciate the help
olejoedad OCT 06, 07:34 AM
Many Fiero owners have been known to run an extra ground strap from the engine block to the space frame to ensure good grounding.
buddycraigg OCT 08, 08:41 PM
Every fiero I have ever owned has done that. Don't worry about it.
My 87 S-10 pickup does it too.
ReptilianRascal OCT 09, 01:46 AM

quote
Originally posted by buddycraigg:

Every fiero I have ever owned has done that. Don't worry about it.
My 87 S-10 pickup does it too.



Thanks but unfortunately we've got pretty strict registration rules here (NSW, Australia) and sometimes, with the people who decide if a car can be registered or not, you'll get one who says "yeah, sure, no problem" and you'll get another who says "no, even if you get this fixed" and then there's a bunch of responses in between those 2 extremes.

I'd rather try to present it in as good a condition as I can to smooth out the red tape as it's already a little rough around the edges with the paint
Mike in Sydney OCT 09, 06:21 AM
Hey, Rascal. Check your PMs. I'm in Meadow Flat near Tarana. Got two '86 GT's. Have owned Fieros since '91.

Mike
theogre OCT 09, 09:52 AM

quote
Originally posted by ReptilianRascal:
Thanks but unfortunately we've got pretty strict registration rules here (NSW, Australia) and sometimes, with the people who decide if a car can be registered or not, you'll get one who says "yeah, sure, no problem" and you'll get another who says "no, even if you get this fixed" and then there's a bunch of responses in between those 2 extremes.

I'd rather try to present it in as good a condition as I can to smooth out the red tape as it's already a little rough around the edges with the paint

I'm guessing your inspection is similar to MOT in UK that covers many things beyond most inspections in US including NY and maybe others that puts cars on a lift to look at bottom. MOT recent changes can fail you for having "Light Upgrades" for Headlights etc too because most "upgrades" are crap and illegal.

Ground behind radio and many more need to be looked at including everything bolted/screwed to frame or engine in back.
check 12v to + "box" under C500, battery and alt cables.
Clean/fix and coat w/ silicone or brake grease to keep out "water."
buddycraigg OCT 09, 01:04 PM
Ah. I didn't realize that you were going to have an inspector getting all up in your business.
If you really HAVE to fix it, I would say checking the grounds sound like a good place to start.
theogre OCT 09, 03:10 PM

quote
Originally posted by buddycraigg:
Ah. I didn't realize that you were going to have an inspector getting all up in your business.
If you really HAVE to fix it, I would say checking the grounds sound like a good place to start.

UK MOT and countries are way more strict... Far worse then most or all US states that have inspections.
Very old video aim at inspectors and shops... ~ 30 minutes https://www.youtube.com/watch?v=QcG-_w-he2Q
More recent to show the public a complete and passing MOT for a car. ~ 52 minutes https://www.youtube.com/watch?v=tBORGEXmlYU
More of same but shorter... ~ 18 min https://www.youtube.com/watch?v=YWNshqPS9Ys

If they see HID or LED "upgrades" in car came w/ Halogen HL recent changes can Fail you even if output pattern looks ok to you.
Even w/ Legal HL you can Fail just for bad alignment, dim bulbs, etc. because of the HL "machine" briefly shown in all above.