Ghettobird52

Hey all long time no talk!

Ive been having a Fuse problem with the 10a "gauges" Fuse. It was blowing randomly for a year id say about once a month. I would just replace the fuse and i was good for another month. Well about two months ago, the fuse started to blow, and instantly blow every time i turn the ignition on. This leaves me with no gauges (though they still light up) and when the headlights are on the chime beeper never stops. When the fuse blows the gas gauge goes all the way up above full and stays there while the fuse is blown.

So today i decided to tackle it (i have another car i was driving lol) and took apart my whole dash. I Searched and found these as common problems things to cause the gauge fuse to blow

Chime Module (In the Convenience center)
Cruise Control Wire
EGR
AIR (both connectors)
Purge Canister
Aftermarket radio (which mine still works when the fuse blows)
Headlight Switch(and Interior Dimmer Switch)

I have all of these unplugged and the Fuse continues to blow. I just pulled out the whole Instrument Panel and the fuse still blows with the Instrument Panel Disconnected??

I remembered (because i havent drove the car in over a month) that in the past 2months when the fuse was good, occasionally the Fuel gauge would act very odd, it would drop all the way to empty, then back to half way, then up to full, then back down to empty, and sometimes stay at a weird location, other times it would come to my current position, which sometimes was full, 3/4 and half way, but the guage would dance across the Empty to full.This now has me thinking that the Sending unit is faulty, with an 'open circuit'? (correct me if im wrong) thats causing it the read at Full? And thats whats causing the gauge fuse to blow?

Any information or things i should try (i have a multimeter but not good with it) i would be glad for any help!!

Thanks all

AlkyIROC

Use a wiring schematic to determine everything on the circuit that the fuse is protecting. Build a circuit load tester. With spade fuses it's easy. A couple of spade connectors with wires going to something like a headlight. Install the spade connectors in where the fuse normally goes.

With power on, if there's a dead short in the wiring, the headlight will come on. Start removing items from the circuit until the light goes out. When the light goes out, you're removed the circuit going to ground. Trace that circuit and find the short to ground. With everything disconnected from the circuit and the light is still on, you need to start doing a harness wiggle test.

The headlight simple puts a load on the circuit. If the circuit is shorting to ground, the circuit is complete and the headlight will light up. It's a lot easier than guessing and constantly putting in more fuses to see if they will blow.

Fuel gauge is powered from the dash. Fuel sending unit works off a ground circuit. Shorting the wire to the sending unit will only cause an incorrect reading but won't blow a fuse.

OrangeBird

iTrader: (1)

Are you aware that the 10 amp gauges fuse supplies power to the A/C compressor clutch relay on a pink/black wire ? I ask only because those relays under the hood seem to be notorious for having the wire insulation near the connector getting bare and causing all kinds of electrical mayhem . Anyway , to answer your question , the gas gauge will of course be affected by the power irregularities caused by whatever is shorted , but it's not too likely to be the gas gauge nor sender themselves causing the short circuit . If you short the sender wire to ground it will send the gauge below "E" , but it will not blow the fuse (similarly , if you open circuit the sender wire , the gauge will peg above "F") . Your best bet is to look for any wires that may have been tampered with in the past , as those are likely spots for shorts to happen . If it's not obvious , you may have to dig into the harness far enough to find where the wire from the fuse branches off to feed all the different things that fuse supplies , open all the branches , and measure each with the ohm meter , looking for whichever branch reads 0 ohms (that will of course be your short) . Lets hope you find the short externally of the harness , so before you go separating any branch circuits , really inspect every inch of the under hood and dash harnesses , you may save a lot of untaping/retaping time if you don't have to actually iopen up the harnesses to follow wires ....

Good Luck

OrangeBird

iTrader: (1)

Alky beat me by 13 minutes on the post , but our ideas line up pretty well ....

Scorpner

iTrader: (4)

I hesitate to post because I don't want to complicate things. I have a different way of doing the same thing and it may help either from the method used or by helping understand in a different way.

Same idea as the circuit load tester, but I usually disconnect the battery and use a multi-meter (set to ohm or beeper mode) when looking for a short in the circuit.
If it isn't an individual component (radio, relay etc.), then moving the wiring around beforehand can cause you to lose the opportunity to find the short because if a worn section is touching the body, it would have to fall back into the exact same position for it to re-occur.
Same with either the circuit load tester or meter, it is important to have it hooked up and then disconnect (components) and or check the wiring via jiggling/moving. Once the light goes out/or it stops beeping, you need to reconnect/or move the wiring/harness back to see if you can get it to come back so you can verify that you found the problem.

Fuel gauge:
I agree on the gauge being a symptom of the short altering the circuit. It depends on where the short occurs in relation to the gauge and the rest of the circuit involved (Ie. it could go low or high). A method via an understanding of electronics and a schematic might help locate where the short could be, but hands on would most likely be faster in finding the short. With the instrument panel removed it was most likely a symptom and not the problem.
*A schematic would be more useful in identifying what components to disconnect and what wiring is involved. Even though you searched online and found components suggested to be in the circuit, you need an actual schematic to create a list that is legitimate. These kind of things should be done in a certain order and in a purposeful way so that you don't cause more problems than you started with.

Reply to the gauges and lighting:
The gauges still light up because they are on a completely different circuit. Lighting is on a dimmer circuit that varies in voltage levels, this includes radio, gauges, interior lighting etc. In contrast, the actual gauges etc., need a constant voltage source, and separate inputs. The circuit/s you are concerned with include the separate inputs (and the door chime). That's why you notice some things affected while others are not.

All this said, multiple issues are often caused by bad grounds. When a circuit is not grounded, voltages can float and cause unpredictable problems. If you have a problem when you turn the headlights on I would check for grounds up front by the battery, they are for the headlights. Then also the headlight switch itself. The engine has a ground strap at the rear passenger side as well.

I hope that helps.

Ghettobird52

Ok thanks all, So was i testing items correctly, by Popping in a new fuse, unplugging a item and turning ignition on (to have the fuse pop obviously) ? Or was my testing invalid and i should button up my car and start all over? Right now the car is still torn apart with the instrument panel out, ect. If i did test correctly can i rule out that all those items are not causing the problem?

Yes i tested the AC with both plugs unplugged and a new fuse in, still blows.

What you guys are saying about the sending unit, or what i am getting, is that even if the circuit is short or opened (as it appears to be on my situation as it shows above F) on the FSU, it will give the read out (Full or Empty) and thats it, it wont affect anything else? Thats why i was able to see it jump around while the rest of the guages were still good? so i can rule out the actual fuel sending unit as the problem then? Question: If the Fuel Sending Unit should still send its signal if no problem, why when the fuse blows that gauge still doesnt read normally if its on a separate circuit?

Should i put it back together and restart, or am i safe to say those items are good and look else were?

Edit: Does anyone have any Wiring Schematics for 88 Firebird 5.0 TBI (originally)? I can find a few on Autozone.com but it does not show the fuseblock wiring, only engine wiring and body wiring. Any help is appreciated! Thanks all

Scorpner

iTrader: (4)

Yes, if you are still blowing fuses after removing components, then the short is still there. You could also leave everything unplugged until you find it, or alternatively put a tester or meter on the fuse location as it sits, and start moving wires around to see if it's wiring related.
FWIW, sometimes when a component shorts out it can knock out other components down the line. This just happened to someone with a really bad short because the current was enough to cause large amounts of smoke. That's why if I know I have a short I prefer to use the meter instead of testing live. Your fuses are protecting the circuit (by blowing out) so I don't think anything was damaged in your case.
Anyway, if you have two bad components then when you plug in one or the other in you will still have a short. It's not that common though. Obviously, when you have the components unplugged you have to make sure that you don't have an open connector touching the engine or body, or can move to where they can. So instead of thinking of the steps as in testing each component and then putting it back into the circuit you might want to think of the steps strategically and in a way that is less likely to reintroduce a possibility.

What I'm basically getting at with the fuel gauge is to leave it out of the circuit until you find the short. At this point it's more of a symptom. Once you find the short and if it acts up when you plug it back in, then it becomes s problem to deal with at that time.

There actually was a 1988 Firebird PDF floating around, you may come across it if you search the site for it. Austinthirdgen.org also has schematics, but I'm not sure if they have what you need.
http://www.austinthirdgen.org/?pid=19

Scorpner

iTrader: (4)

I saw this the other day. It would definitely be nice to have, some local auto parts store rent tools and may possibly rent these too.
Anyway, it also demonstrates the basics of a circuit and how a short occurs.

nater

also test your ignition coil, on my old v6 berlinetta this guse kept blowing and i couldnt figure it out. it wasnt untill one day when i was setting the timing on my v8 berlinetta and the brown wire to the distributor (goes to ecm and tach in dash) grounded out. it blew this fuse and i made sure the wire was well away from any ground, replaced the fuse and everything worked again. to test id suggest just unpluging the brown wire, if it stops blowing fuse your problem is probably in the coil.

WickedBowtie

So what if you have the fsu out of
Tank but still plugged in and the gauge reads correctly as you move the unit. But once I put it back in tank it stays at 1/4 tank all the time. Even with key out of ignition.

FlumpDuster

I have this same problem in current time still cant figure it out

zacharyhorn

iTrader: (1)

thank you sir.

zacharyhorn

iTrader: (1)

My Fuel gauge is the same. 3/4 full of ethanol.

Ivo_NL

Maybe I found the solution to this blowing fuse horror, mine did the same, turns out the TCC solenoid in the automatic gearbox is stuck, just unplug the conector at your gearbox to check...

sofakingdom

iTrader: (1)

That fuse feeds a YYYYYUUUUUUUUUJJJJJJJJJE number of things. In addition to the gauges themselves, practically every solenoid and similar thing under the hood and in the drivetrain is on it. If you look at any connector and find a pink/blk wire, it's fed off of that circuit. The transmission is definitely one of those things, as Ivo notes. Unfortunately that means that there are about a million places where a wire could get chafed or a component can go bad (develop a short) or whatever, that can blow that fuse. It has to be one of the least fun circuits in the car to clear a fault on.

Ivo_NL

@sofakingdom thanks for your reply, I guess your right, it was a horror trip chasing that pink/black wire.....
Today I put a new TCC solenoid in, and broke off the connector on the (4th gear ?) pressure switch next to it grrrr..... so still no functioning lockup in my trans but the gauges fuse is still good....now waiting for the new pressure switch to come to Belgium and hoping it will work again.....