I was driving my green 51 and temp. said hot But it wasn't hot at all. GAUGE OR SENDING UNIT ???????

 

Is it a 239 flathead? I believe that they have two sending units, one for each side. If it's the flathead 6, then it should only have one.

I'd replace the sending unit(s) first. Do you have an infrared heat thermometer? If you do, measure the heat with it when the guage shows it to be hot to see what is the actual temp.

 

YA ILYA its a V8 flathead. Heck i know it ain't the smart thing to do but i removed the radi. cap and it wasn't hot . I'm guessing i'll have to order the units cause i went to get a 6 volt taillight bulb today and they didn't even have that at the local parts store. Man i luv driving the stock 51. I learned to change gears with out pushing the clutch. ITS ALL ABOUT TIMING !!!!! LOL

 

Hey Dale, if it worked when you first bought the truck, you might want to just check the back of the gauge itself and make sure it's getting power before you go any further. With these 6 volt positive ground systems, the gauge falls to hot when you turn the key off. Who knows, you might get lucky and find a loose terminal back there or a loose power wire coming from your ignition. But otherwise, I agree with Ilya. It's probably the sending units (remember they are two different types of units and you have to have both).

You need an 1154 bulb (double filament). I know for a fact that Advance carries them on the shelf. Don't forget to check the ground and make sure it's making good contact back to the frame too if the bulb looks good in appearance. I'm glad you are able to drive your truck. I told you the flatheads were very fun to drive. And eventually you'll realize (like me) that paint job isn't all that bad and it's a heck of a lot more fun to drive it around and enjoy it.

 

Did it start out reading C, and gradually go to H, or was it on H the whole time? It could be the sensor that has two terminals is bad or has a loose wire. It will send the gauge directly to H.

 

think it starts about half way then go's to hot. SO if i replace both sending units i will need a single post and a double post ?

 

Yeah, a wire goes from the single post to one of the double posts, and from the second post to the gauge.

Keep us posted.

 

I drove it again 2day and it is on hot when i crank it then it will go to cold and work its way back to hot after about 10 miles. These sending units cost 50 dollors EACH from classic haulers. So i need to know for sure before i pay that.

 

Key on, engine not run yet today: needle should slowly go to C
Key off: Needle will be on H

The two-post sender is a switch; it should read close to 0 ohms across the terminals at anything less than 200 degrees.

The 1-post sender will have resistance at all time from the terminal to ground. If no resistance (no continuity), it's shot.

 

THANKS ROSS

 

Why not try hooking up one sender at a time? Be pretty rare for both to go bad at the same time. I've run only one sender on all of my flatheads through the years (50). Chack the thermostats for sticking. Take the rad casp off and fire it up and check for bubbles(head gasket or cracked block).

 

You really can't use the two-post sender by itself, it would do nothing unless you ground the post that goes to the 1-post sender, then the gauge should read C all the time. You can run with just the 1-post sender, in either head, and the gauge should work normally. You can short the 2-post sender's terminals together to accomplish the same thing with a lot less trouble.

 

Albuq F-1 I bow to your expertise. Too much electricity for me! :-)