So I have a 1969 Coupe and I noticed my gas gauge and my temp gauge is not working but the speedo and RPM does. Possible fixes or reasons why those 2 specifically wouldn’t work?
Gas Gauge may not work due to fuel float, being full of fuel. This happens when float develops a crack/leak, and float fills with fuel. This means the float, not longer floats. You will need to remove gas sending unit form the gas tank. EZ job if gas tank is low on fuel. No need to remove the tank.
Good chance the temperature sensor on the manifold is bad. Pull the lead off the sensor and ground to the block, to see if your gauge slowly climbs to hot. If it does, most likely indicates a bad sensor. Replace with Ford Motorcraft unit.
I experienced these exact same things, and that is how I solved those issues, on my 1970
What TCELL says could be your problem. Here is another possibility. It could be the IVR, instrument voltage regulator, has gone bad. The speedometer would not be affected as there is no electrical to it. If your car is a factory XR7 and has the factory tach that would not be affected as it has its own electric supply to it. Did the gauges work before?
A third possibility is due to the metal housing of the back of the dash cluster. If you recently replaced the circuit card, you had to unscrew the bolts holding the gauges in place. These two bolts stick up through a small metal rectangle in the dash cluster housing, and once re-assembled, are covered by a cardboard insulator, the circuit card, and the nuts. It is impossible to see if either bolt is touching the metal housing, which shorts out the IVR signals and your gauges (other than an ammeter) will all appear to be dead.
To check for this situation, remove the dash cluster, unhook the circuit card from the IVR, and measure resistance between the gauge posts and the metal housing. If you see 0-1 ohms or 14-17 ohms, somewhere one of those posts are shorted. Re-set the gauges until you see high kilo-ohm readings.
You did not mention the oil pressure gauge. If it is also not working that points you to the Instrument Voltage Regulator. It is common to those three gauges.
Wouldn’t it be great if there was a way to verify the gauges were all working correctly and that the IVR was doing it’s thing? LOL!
Here is your trouble shooting solution $30 shipped in the US. You don’t need to pull the cluster to test.
So I don’t know if it makes a difference but the car is non xr7 it’s a sport (don’t know if there’s any electrical difference). As for if they worked before, I’m unsure I bought the car over the weekend the owner said it did but you never know. Also side note I did notice at some point the headlights and the radio would flicker on and off but the car seemed to never lose power. Don’t know if that could also mean it’s a battery issue?
So the car sat for some time before I bought it and the fuel was old and it was trailered about 8 hours on bumpy roads so I’m not sure if that could effect the fuel float at all or get it stuck but I am gonna look into the temperature sensor and see if that makes any difference. Also while I see you have the same motor I’m gonna ask a dumber question. I am 22, I have had newer corvettes this is my first “classic” the oil also needs to be changed. What oil should I run I see a lot of 10w-30 but I could never get a for sure answer. Also what gas should go in? 87,91,93? It’s just a stock 351w (crate motor from 2005 ish)
Oil is dependent on temperature the car is operated in. Back then oils came in 10W-30, 10W-40 and 20W-50. Same as today except now you have more choices. If you live in Death Valley or Saudi Arabia you would want a thicker oil like maybe a 50 weight. In Norway inside the arctic circle you might use a 30 weight.
10W-40 should cover Missouri temps just fine. Multi viscosity gets you the equivalent of 10 weight oil when cold and 40 weight oil when hot. And you can run 87 octane regular fuel unless it causes pre-ignition ping. I use non-ethanol fuel in mine since it easier on rubber parts and seals. Get that old fuel flushed out before you drive it. Your fuel sender is probably a rusty varnished mess like mine was.
Entirely true. The 69 and 70 housings were metal (which is why I responded to this particular post of having a 69), but FLM changed over to plastic housings in 71 for the most part.
