Temp gauge has me baffled?

[Guest Dodge Deluxe]

Folks;

I bought an NOS temp gauge last fall for my '39 Dodge as the one in my car was broken. I was fortunate enough to find a brand new old stock 1939 Dodge factory gauge still in the original box, it was unused. I installed it and to my disappointment it did not work, the needle did not move as the car heated up to operating temp. Oh well, so installed an under the dash aftermarket one and it did the job. Just for sh*ts and giggles I took the NOS one and put the bulb in a pot of water, and set it on the stove. When it started to get hot, the gauge needle started to move and when it came to a boil the the temp gauge was reading perfectly. I just re-installed it now, knowing that it works as I saw it with my own eyes, I started the car, let it get up to temp, and just as before the needle does move at all??? I'm baffled on this one. I know the gauge works, I know the coolant is hot at the fitting where the bulb goes into the block as it it too hot to touch, so what's going on?

Dan

[Guest simplyconnected]

Capillary tube thermostats have no idea where you mount them, and they don't lie. There is alcohol in the bulb. When heated, the pressure raises (making the needle move) PERIOD.

Somehow, your bulb is not in contact with heat. Is the bulb submerged in coolant? If it works outside your engine, it should certainly work inside. Maybe your coolant level is below the bulb.

[RickBrinker]

Check and make sure the hole into the block isn't plugged

[Guest Dodge Deluxe]

Thanks for your replies. When I remove the bulb from the block, coolant pours out, so no blockage and it must be making contact, this is why I am so stumped?

Dan

[Guest imported_woodwheels]

Dan; Is the water temp needle bent? Outside of the dash it is moving freely. With it out of the dash look at the position of the needle at a very oblique angle. If it is not parallel to the face of the insturment carefully bend it to the parallel position and reinstall. Is the length of the needle exactlly the same as the other 3? If it is longer is may be hanging up on the face of the dash.

Jim

[Guest DodgeKCL]

I agree with 'woodwheels' Dan. The only remaining plausible fault would be the needle is rubbing on the bezel (glass). With a pair of tweezers carefully bend the needle back ,at the place where it bends at 90* coming out of the back of the guage, towards the dial face til it just clears and try it again.

[Guest Dodge Deluxe]

Well, you guys were right. I took the gauge out of the dash this evening and let it hang under the dash while I started the car and let it warm up. Sure enough as the engine heated up the gauge started to register it no problem, so I figured it must be as you said and be obstructed in some way while it is installed in the dash. The needle looked okay, but in comparison to the old one that I took out, the stem coming out of the spring that the needle pivots on was slightly longer, and as such I determined that when I was tightening the screws that hold it in I was compressing it against the inside of the dash window. I put a small washer between the dash window and the gauge at each screw hole for the screws that hold it in to use as shims and tried it again, and that did the trick. Gave it just enough clearance to function properly now. Thanks for the help all.

Dan

[Guest 1930]

This was a good post and I definitely learned something and thanks for placing it here and all the responses

[Guest GP Gleason]

You always want to check those mechanical temp gauges before you install them....... even NOS ones. Check 'em on the stove in boiling water, then install the bulb end into the engine Run the engine to operating while constantly observing the gauge to see if it still functions properly. Mounting into the dash is the last thing to do.

Glad you found the trouble!