So I just an 87 v6 se that sat for four years, other than a few minor issues she runs pretty good. My main concern I'd like to fix before a consider daily during is the fuel and temp gauge. Not so much the fuel, but definitely the tem . I've looked around on other sites and found that it can be commonplace in cars for both gauges to go on the fritz. Which leads me to you guys, who better to ask than fiero experts. The temp gauge runs cold and doesn't register while the gas will register too full or mostly full. Before I starting dealing with them as separate issues I wanted to see what you guys thought about it maybe being one issue affecting both gauges
Originally posted by phonedawgz: They are separate issues.
Not completely. If both are dead... dash circuit "board" might have problem. They get power from gauge fuse and iffy dash can block power to any or all gauges.
Iffy readings could be the same, ground/wire problems, iffy senders, or any/all of them.
Example: The gauges connect to back of dash w/ spring chips and can get dirt/corrosion making poor contact. Poor contact could add resistance, low/no power, etc.
------------------ 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)
First off I'd like to apologize for the grammer errors on my original post. Now, I've been learning how to work on cars myself and although willing to learn, the electrical part seems like it might be over my head. I do have the Haynes manual. What I gather is I'll need to buy a multimeter and see if the wires to and gauges are reading correctly? And find out where the issue is coming from. I'm not sure what everything would read if they were good or bad.
Invest in a paperclip. Then use it to probe the leads of the coolant sensor connector, which is located on the trunk-side head on the corner next to the coil and hoist eye bracket. Use the paperclip to ground The connector leads, one at a time, to the engine block and look at the gauge. If the circuit is good, with ignition on, you'll see either the guage peg out our the idiot light turn on. For the fuel guage, figure out which lead of three is the sender. One will be ground, one will be power and one will be the sensor. The connector is located on the back glass firewall in the center around the booster vacuum supply hose. The power will run a test light or show voltage on a multimeter for two seconds when key switched to on. The ground will ohm close to 00 to the chassis, which leaves the remaining lead to be the sensor. I don't know the wiring colors, maybe someone can correct me on that. Again, with the paperclip, ground the sensor lead and watch the guage peg out. If no movement from either test, look into the ogres info and check out the dash board. Edited to add: The paperclip is a Swiss army knife to the fiero. You can use it to jump relays, troubleshoot, read ecm trouble codes and history, stab thieves, secure very small cargo.
[This message has been edited by f85gtron (edited 12-03-2016).]
Originally posted by f85gtron: Invest in a paperclip. Then use it to probe the leads of the coolant sensor connector, which is located on the trunk-side head on the corner next to the coil and hoist eye bracket. Use the paperclip to ground The connector leads, one at a time, to the engine block and look at the gauge. If the circuit is good, with ignition on, you'll see either the guage peg out our the idiot light turn on. For the fuel guage, figure out which lead of three is the sender. One will be ground, one will be power and one will be the sensor. The connector is located on the back glass firewall in the center around the booster vacuum supply hose. The power will run a test light or show voltage on a multimeter for two seconds when key switched to on. The ground will ohm close to 00 to the chassis, which leaves the remaining lead to be the sensor. I don't know the wiring colors, maybe someone can correct me on that. Again, with the paperclip, ground the sensor lead and watch the guage peg out. If no movement from either test, look into the ogres info and check out the dash board. Edited to add: The paperclip is a Swiss army knife to the fiero. You can use it to jump relays, troubleshoot, read ecm trouble codes and history, stab thieves, secure very small cargo.
Sender short to ground will read Empty/0psi for 90Ω fuel and OP gauges. ~45Ω is half scale, 90Ω is full scale, open pegs above full scale. Fuel tank is C502 at that location Pink is sender, Blk ground, Tan/Wht is Switched power to pump.
Fuel test... Jumper any resistor = or < 90Ω to C502 pink to black then pink to frame or engine. If gauge reads different... Could be iffy grounds in the cabin or elsewhere. Check/clean/fix G201 and G202 and all in engine bay. See my Cave, Wire Service
If temp gauge/light is OE... Pegs Gauge w/ Key turn to Bulb Test and Start. Light is dark. If guage/light is fully fixed... Light is on w/ Key turn to Bulb Test and Start. gauge does nothing. Otherwise gauge does peg high or above w/ short to ground, 55Ω=260°, 1365Ω=100°F Sender is block ground and iffy grounds will make it lie. Note: Temp Gauge Sender does not = MAT/ECM sensor resistor values. Both Sensors are only 1800Ω at 100°F and does not ground to block.
All data here is charts etc in FSM book and alldata. Unlike Haynes/Chilton, Alldatadiy.com is accurate for year of car because all data they used came from GM and other car makers.
[This message has been edited by theogre (edited 12-03-2016).]
So my fuel gauge works as advertised but not the temp gauge. When I ground the temp sensor with a paper clip to the block one side lights up the temp light like it should. The other side Meeks the gauge peg, but to at full temp to zero. Gauge always sits at 100* hash with vehicle off, KOEO, or when engine is running unless I ground it then it moves backwards. Any help? Tate
[This message has been edited by PontiacTate (edited 12-05-2016).]
So my fuel gauge works as advertised but not the temp gauge. When I ground the temp sensor with a paper clip to the block one side lights up the temp light like it should. The other side Meeks the gauge peg, but to at full temp to zero. Gauge always sits at 100* hash with vehicle off, KOEO, or when engine is running unless I ground it then it moves backwards. Any help? Tate
be aware that the Fiero temp gauge wiring is goofy from the factory. Not sure this is part of your problem: you may want to edit your post (so we can understand it).
Guages w/ key off mean nothing. Meters do not 0 w/ key off. Key on then Gauges should read sender value.
Temp gauge could be: bad Gauge or wiring is getting bad connection. Needle moved. Adjustment: Need ECM scanner to read ECT is easy and set gauge to roughly match. resistor on back (inside dash) is getting bad connection. Do Not over tighten nuts! You will wreck resistor on the ceramic. These resistors are part of "programming" for gauge "accuracy." {Gauges are never 100% accurate.)
I did the rewire at the sender and control panel when I got the car as well as installed a new sender and new fuel/temp gauge due to the gauge not working when I got it. It has never worked and when grounding out the sender the needle moves backwards from the 100* mark (where it always stays) to full negative. I have no clue how to fix it. Everyone talks about ground it out and it pegging but no one seems to know what to do if it pegs the wrong direction. Tate
The fuel sender is notorious for weird operation and can be way off. The first tip I use to troubleshoot is to fill the tank all the way full. If the sender and gauge are working close to normal, you will see the needle go somewhere near full. It can vary from just above the mark to just below the mark. Most of our cars get about 15 to 20 MPG. Drive for about 80 miles and it should be somewhere around half full. If you hear a weird "whistling" or groaning sound from the center of the car around 150 to 175 miles, you are very near empty and the gauge should reflect that. The fuel pickup starts to suck air plus fuel when really close to empty and it makes that groaning sound.
The temp gauge can also vary. Both of my 88 GTs read way low. They barely move off the low end and both have 190 degree thermostats. Kevin's red one had the gauges replaced and I never calibrated them. You have replaced your gauges, so your gauges ought to be good. Sounds like something is off with your temperature sending unit.
You can get a new temperature sending unit from Rock Auto for $12 vs $19 at the Fiero Store or AutoZone. If you buy a Digital Voltmeter, you can measure the sending unit while it is cold and get a good idea if the resistance is correct. If it is good cold, it is very unlikely that it will be bad at other temperatures.
Look on Amazon. You can find a thermocouple meter for about $35 that comes with two thermocouples. Definitely a good buy if you need to measure temperature pretty accurately. I was concerned with how hot my engine was getting, so I put the thermocouple on the radiator fins when hot and measure 180 with a 180 thermostat installed!
The other thing you will *never* regret owning is a good digital volt meter (DVM). You can find a nice one on Amazon or through Mouser or DigiKey. You don't need a really expensive one. You can find something roughly equivalent to a Fluke 83 (but not Fluke, they are overpriced) from perhaps Agilent for about $100. Santa should probably know that you are looking for these instruments :-)
You should also look for an actual GM factory service manual for your year car. If you do more than two repairs with it, you will have paid for the book. That is especially true for electrical stuff.
The one place where the factory manual is total junk is for the radiator. Somehow some idiot copied the section for the X body vehicles that were the basis for the FIero and no one ever did a proofread on that section!!!
I have an 88 service manual, so I can scan the appropriate wiring diagram and get it to you if you want to send a private message.
OK. I found lots of interesting information on page 8A-80-0 of the service manual. It turns out that you should see the temp gauge peg all the way hot when you put the ignition to the start position. Oddly, the switch diagram describes Accy, Lock, Off, Run, and Bulb Test/Start. My Fiero only does Accy, Lock, run, start. Not sure there is a working bulb test position.
However, according to the wiring diagram the start position grounds the indicator side of the temp gauge when in the Start position. So, try that to confirm. It should also go all the way to cold when in the run position and actually cold.
The sensor is likely a negative temp coefficient themistor since it is supposed to be 1385 ohms at 100F and 55 ohms at 260F. This is the temperature sensor/switch connector "A". Connector "B" is the switch so when cold, that pin on the sender should be open to the block. Pin "A" should measure probably about 2000 ohms when stone cold like right now. Using your DVM and disconnecting the cable from the sender, you can measure from block to the pin. Pin "A" i where the light green wire connects to the sender.
You can also verify the sender by running the engine to operating temperature. Measure Pin "A" and it should be 100 to 200 ohms or so.
Also, DO NOT use teflon tape when installing the sender. it makes it not work!!!
I appreciate everyone being so helpful. The next day I have off I will reread your replies and see what i can figure out. Some of it seems a bit over my head, but so did changing a tramsission at first, but I tackled that and succeeded so we will just have to see.
Originally posted by Ray_and_kevin: OK. I found lots of interesting information on page 8A-80-0 of the service manual. It turns out that you should see the temp gauge peg all the way hot when you put the ignition to the start position. Oddly, the switch diagram describes Accy, Lock, Off, Run, and Bulb Test/Start. My Fiero only does Accy, Lock, run, start. Not sure there is a working bulb test position.
Bulb test is a valid position but very narrow when turning to start. Bulb test also stays active trying to start. So...
code:
name switch lock pin Accy Accy Active Lock Off Active Off Off Off Run Run Off BTest BTest Off Start BT/Strt Off
AT cars Park Interlock prevents turning key to lock w/o being in park.
I already covered how gauge works. How gauges are wired in the dash: (Not covered accurately by FSM and others.)
Temp Gauge pins are (back view, view thru windshield) top-ground left-12v right-sender input bottom-not used by car. Resistor between top & bottom = ~95Ω sender, again, 55Ω=260°, 1365Ω=100°F but can be outside of this and is normal at low temp.
Fuel right-12v left-sender bottom-ground Resistor between left & right = ~83Ω Sender 0 to 90+Ω gauge reads 0-empty, half tank-45Ω, full-90Ω
Resistor = ~xxΩ because resistor have ±y% tolerance. Fuel resistor spec could be 80 to 85Ω ±2-5% means 83Ω is good. add that many meters and leads aren't very accurate under 100Ω for several reason I won't cover here.
Gauge test... Warning: Test resistors between 12v and Ground can fry very fast and burn you. Worse for low values. Unplug sender test w/ resistor(s) on back of dash between sender and ground pins. Anything between two max values with show quickly gauge works or not.
[This message has been edited by theogre (edited 12-06-2016).]
