Hi everyone.. I am the proud new owner of a super clean 1995 F150. It has the 300 I6 and 5 speed with 80K OG miles on it. I cant seem to figure out the temp gauge on the dash. It does not come to life with the key on and does not register any temperature at all. Where can I start with trying to fix it? Is it as simple as a fuse, bad connection at the gauge, sensor or sending unit? What wires do I need to trace and track down?

I just got this truck and am looking forward to diving into it. I have been working on old VWs for almost 20 years, MOPARs before that. This is my first Ford, so though i am not new to turning wrenches, I am kinda in unknown territory.

 

Take a screwdriver and ground the temp sender terminal to the block. If the guage pegs, the sender is bad. The sender is just a rheostat the regulates the negative current

 

I replaced the temp gauge sender (sensor? the one with the single wire in the block) to no avail. I grounded the wire to the block... no change. So it has to be either the gauge itself or the circuit path. How do I check continuity for the wire?

Also, with the key 'off', the needle points at the 'C'. when I turn the key 'on' the needle actually drops lower- its going in the wrong direction. What is going on here guys?

 

If your fuel gauge is working then there shouldn't be a problem with the power and ground portion of the instrument cluster since the indicators themselves share the same power and ground circuit. However there is a slight difference between trucks with a tach versus one that doesn't. Probably not worth explaining just yet. As Jimmy said the temp sensor is a potentiometer that uses the engine block as a ground and its internal resistance varies when it is hot or cold. 74 ohms cold, 9.7 ohms hot.

Its wire is R/W (red/white) and makes a straight shot to the instrument cluster pin 11 however, the 4.9l has 3 connectors along the way, C125, C101 and C202.

C202 is the big firewall connector by the column , C101 is located on the drivers side fender apron. C125 the book is conflicting, it doesn't show it in the component location view but in the index says its on the LH side of engine near oil pressure sensor.

I am using a 1990 F150 Wire manual, however I have found that while there are some differences in due to technology advances, I would guess the temp sender is the same configuration. BUT, I cant be 100% sure.

 

Update: I was on the freeway this evening and I looked down and the temp gauge was working. The needle was squarely over the "R" in "normal". Then I had to stop for gas. After I filled up and started the truck and.... You guessed it... It doesnt work again. It does that annoying thing where the needle pegs below the "c".

W.T.F?

Thanks for the info on tracking down the red/white wire.

 

Ford uses a push on connector to the temp bulb. Sometimes they spread out a bit and don't connect as snugly as they should. Check the connector, make sure its clean, gently squeeze it together with needle nose pliers, it has a split contact inside and reconnect to the bulb. See if that does it for you.

If not your back to the circuit again.

 

By "bulb" do you meant the actual gauge mechanicals that actuate the needle?

 

Sorry.. we call them temp bulbs on airplanes.. the temp sensor located in the engine block.

 

I have an '89 F150, 302 EFI. My gauge has never worked. Grounding the connector and switching key on causes needle to peg. I replaced the sender, but so far, still no normal gauge function. I'll try cleaning the connector.

 

Same problem here only with a '92 F150. Temp gauge never has worked.