I have a '90 F150 with the 5.0. A while back, the temp gauge stopped working. I figured the sender went out, but haven't worried about it, as the truck has never had any cooling problems. I decided recently that I might ought to seriously consider taking care of it though, so I started searching on here. This brings me to my findings and question(s).

Currently when I hit the key, with everything connected correctly, the temp gauge needle falls slightly from its resting position toward Cold.

I tried shorting the connector and hit the key - it does the same thing.

I tried it with the connector not shorted, and not connected to the sender - same thing.

Decided to see if starting the truck with the sender shorted would give a different result (I was desperately looking for that swing to H, indicating only a bad sender), but got the same barely moving to full Cold, and a CEL; and a drop in idle.

What does all of this indicate? Bad gauge? (please say no - LOL!) With the gauge shorted, and the engine started, I got the CEL and a low idle. Does that mean anything?

Thanks in advance,


Wade

 

It should peg the gauge when you short the sender to a ground. If it doesn't, the gauge is shot.

The stock gauges are junk. Pick up a $20 cap tube temp gauge at the auto parts store. On my 5.8 the included fitting went right in the place of the stock sender, and the tube length was perfect.

I guess you could junkyard-up a replacement gauge, but might as well just get a real one.

 

It means you shorted the wrong wire.
The Water sender connector only has one wire on it.
The one you shorted is the ECT sensor going to the computer and not to the gauge.
I hope you did not hurt the computer.

 

i'd honestly get a mechanical gauge.

 

I wondered about that......:o I've driven it since, though, with no apparent ill-effects. I thought that that was the right connector - unplugged off of [a] temp sensor that was on a stalk coming out of the water neck. ANyone have a good pic of the connector that's supposed to be shorted so i can be sure to do the right one?



Wade

 

Sure, here you go.


/

 

Beautiful!! Thanks subford!! Man, I feel like a moron........ I was thinking that the sensor should have been in the manifold (as that's where it is on my Mustang). I should have known better, but for some or other reason, I saw the ect sensor first and zero'd in on it. :dunce: dummydummydummy......... I'll check the right one now!


Thanks again sub!! (and all)


Wade

 

Okay. Once I FINALLY shorted the correct wire, I found that the sensor is apparently bad - When shorted and ignition on, the gauge swept all the way over to "H". I have a new sensor, but was wondering - would you guys use anything on the threads when installing it? Any type of thread sealer? Teflon tape even?


Wade

 

There is a tube that some auto parts sell that is for sealing and will also conduct.
Teflon tape will not conduct unless the threads cut though it to make contact.

 

Upon doing some more searching, I did find that the threads need to be able to conduct for grounding, as you said. Reckon I'd be okay with nothing on the threads?


Wade

 

May work ok but seems like I may have used pipe dope at one time.

 

The one I pulled looked like it had some of that on it....along with some rust, and oil, and sand, and grime - LOL!! I was thinking between these posts that I may just run some teflon tape around the upper threads (I don't think I have any pipe dope in my plumbing stuff) to hopefully leave some lower ones bare, yet give the tape a chance to seal the upper threads. I just HATE going back in to fix leaks - I want it to be perfect on the first shot! LOL!

Thanks sub.....

Wade

 

It's made out of brass for a reason.Snug it up tight, and a 1/2+ turn should do it. The brass is more malleable & conforms/compresses to the steel threads.

 

As it turned out, I did have some pipe dope, so I put some of it around the tope several threads, and snugged it up good as ymeski said - Sealed up good, and my temp gauge is operational again!!


Thanks all!
Wade