On my 52 F1 flathead 8 just rewired it about a month ago and everything works fine on the guages and all but I might have one problem with temp guage. When you start up the truck the temp guage goes to the half way mark and as long as it is idealing it stays there but if you run it down the road the guage goes just about all the way to cold. When the truck is off it is on the cold mark on the guage. I checked the thermerstat and they are new. The temp cending units are new that I put in on both sides. So should I worry about this or is that the way the 52's run. I am running two gallons of antafreeze in the radirator plus the rest with water. As always thanks for the feedback.

 

is your truck 6 or 12 volt , is it running the oe 6 volt gauges w/ 12 volt , is it grounded good , could be a whole long list of things . hopefully bob j or julie will be along to help ya out . mine acted squirelly due to the half a--ed 12 volt conversion from the p.o. and ran the 6 volt gauges and fried 'em ................

 

Did you screw the sending units in dry or did you use teflon tape or a sealer on the threads? They MUST be screwed in dry to get a good ground and operate properly - especially on a 6 volt system.

Also, is there any chance that you're cooling system has air in it? trapped air can cause weird temp guage readings also.

 

It's reading backwards. Change the wires on the back of the gauge.

They rest at hot when the ignition is off. Turn it on and the needle goes toward center/cold and moves back toward hot as the engine warms.

At least on 48-50's.....I think 51/52 is the same.

 

My 52 has been rewired for a 12 volt system with a reducer on the guages. What do you mean turn the wires around. I have the wire running through the guage holders. I don't understand what difference it would make. Can you explain what you mean. I didn't put any tape on the threads for the temp sending units I put in so they should have a good groung to the engine. Thanks for the help and information you all can give me. If I change the wire and it reads cold now does that mean it is running hot then.

 

Ok lets start at the begining. First, when the ignition is off, the temp gauge needle should be parked on "H." If it isn't then there is a possibility that this is a non OEM replacement or 12 volt gauge.

Second, when you turn the key on, it should travel to "C" then slowly move up in temp as the engine warms up. If you still have a generator on the truck, the gauges will be in a low voltage situation until the engine is turning at over 1100 rpm. It makes about 1 to 2 needle widths difference - less than you are describing here.

Third, what sending units did you get? Are the part numbers on the two the same or are they different - they should be different. I'm not sure if you realize, but the two of them are not the same. One is a variable sender, and the other is an "on/off" overheat switch.

OK, so put all those thoughts in the back of your head.

On the back of the temp gauge there are two studs that wires (or you rreducer) hook up to. As you are looking at the face of the gauge, the one on the left behind the "C" is the stud that should hook to the wire going to the senders. The other stud on the right behind the "H" on the face of the gauge, is where power is hooked up on an OEM application (I have never gotten the gauges to work backwards by switching the wires around, switching polarity, or converting to 12 volt btw)

First, check that your voltage reducer is bolted down to the stud on the same side of the gauge as the "H." Also, check to make absolutely certain that the reducer is properly grounded via the black pigtail. If it's not you will get bad readings, but worse will fry the reducer. Then be sure to check that the reducer is recieving 12 volt power. (See the diagram below for the correct wiring).

Then check your senders to make sure you have a proper pair and not two temp senders or two overheat switches. These senders MUST be the 6 volt sender and switch used on the OEM 6 volt system when yo use the voltage reducer on the gauge.

After checking all that try it again. I'm a little concerned about the gauge itself - should park on "H" so I'm wondering if there hasn't been some type of creative substitution. But honest if the reducer is installed correctly, I'll bet you have two temp senders or a rogue gauge. IOW you have a two variable grounds instead of just one.

Question: have you ever had that gauge work before on 6 volt - prior to the 12 volt conversion? Also, are you using a single reducer for all three gauges?

 

The temp sending units are 6 volt and they did have different numbers when I ordered them because one had two post and the other one. So you think I should check the wires on the back of the guage to see if they are hooked up like the pic you showed me on this. I will check this and does the way it works mean that the engine is running hotter than it should. I am running a 12 volt alternator on the truck but guages are reduced with a little cube at the top of the guage. I ran a reducer wire around to all the guages from that cube which is I think a reducer cube like one of the pics you showed on one of the guages before. Could the wires be hooked up to the wrong post on the guage and that would make a diifference in the guage. I'm a little lost here.

 

No don't be confused, it sounds like you have it all done right. I would venture to say that your engine is fine. If it's running hot, it will smell hot, etc. And there's no reason it should suddenly start running hot right? And you have the sending units in the right places (left and right) on the engine correct.

Try flip flopping the wires on the back of the gauge and see if that fixes it. If that doesn't fix it, send me a PM and I'll send you another Temp Gauge to use - this one sounds a little funky. Did it work before the conversion?

 

don't be afraid to put a thermometer in the radiator. you will know right away how hot it is.

 

Julie

These are the temp gauges I have but they are not the same on the inside. One came on the old cluster and the one on the right is the new one I got. Can you tell if the gauge on the right is the right one or is it the wrong gauge. Is there any reason they would be diffrent inside? We tried switching the wires and that didn't help. When you turn the key on it still starts on cold and when it runs a little while the temp goes all the way to cold. The gauge on the left does not work due to having broken wires inside. Any other suggestions?

 

I can tell right off, the guage on the right is not the same. It's built backwards.
Well, that is to say it's built backwards compared to the original guage. I'm sure that it's built right for whatever application it's meant to be in.

Your temp guage (the one on the right) probably works just fine...it just isn't made for your application. If it were wired up properly in the right application it would probably work like it's supposed to. Instead it's wired up properly in the wrong application (your truck) and therefore working opposite of the way it's intended/improperly.

Can you find any part numbers on the guages? That could shed a lot of light.

-James

 

Well after we checked the wires and changed the guage to another one it still didn't work. Took the guage on the right and changed some wires around and toasted it. My son has his 52 down to the frame so we took the temp guage out of it and now it is on hot when key is off like it is suppose to be but it seems to be running a little hotter than I would like. I mean it runs between the last three marks on the guage when driving I think I will change out the thermostats on both sides to 160' and see if that will make any difference or do you think I should take them out all together? Leave them out will that make a difference in it running cooler wouldn't it. I am not sure if it now has 180' in it or not haven't looked. As you can tell I'm not a machanic when it comes to cars and trucks. Let me know what you think I should do next. Thanks for the information you people have given me already.

 

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Yep, since the original one is broke, you'll need another one. Send me a PM with your address and I'll send you one that works. Keep both gauges and the faces. You can put the new face on the gauge I send you. I didn't think the flip flop on the wires would work, I've never gotten that to matter on the gauges. But it was worth a try.

And the reason it is built backwards and doesn't work is because it's probably a gas gauge for a 56 - probably built up by mistake with the 51/52 face. On the 51/52 gauges all three of them (minus the ammeter which is a completely different animal)have the needle parked at the right with the needle center on the bottom. This one was built up by mistake and because it doesn't work properly WRT Electricity, it's probably a 56 gas or temp gauge - 12 volt! Anything 48-55 6-volt would work correctly.

I tested the one I have and it works fine. You'll have to paint the needle - Testors Model Paints. I can have it in the mail for you tomorrow if you need it.

Leave teh thermostats in it will run cooler with them in because they keep the water from freeflowing through the radiator too fast (and thus not cooling enough).

Also, is the engine newly rebuilt? if it is it will run hot for about 3000 miles. Also, it will not get enough air flow at idle to keep at a good operating temp. The gauge reduce may ahve a little bit to do with this.

First, yo uneed to ascertain the temp th etruck is actually running at - is it really running warmer or is the gauge just showing it warmer. Get a thermometer and test it, or get on eof those laser gun thingies to shoot at the engine to see if it's too warm.

If not, then you can adjust the gauge back down to where it reads on the centerline for normal temperature. Do you see the two holes in the back of the gauge and the little alligator teeth inside them? If you get a very small screw driver blade and GENTLY move those teeth left or right it will adjust the needle. You don't have to move it but about a hairs distance to adjust the needle. Practice on the two bad gauges first.

Don't try to fix too many things at once - one at a time!

 

Thanks Julie for everthing you have done for me on this old truck. I will leave the thermostat in but do you think they should be 160' or 180'? I don't know if the engine is new rebuild or not that is something when I got the truck they didn't tell me. It might be than again it might not be. Can't tell. If was rebuilt the guy didn't paint it before he put it back in the truck because there is some rust on it and paint missing in places. So that makes me beleive it's an old engine.

 

I'm not sure about 160s or 180s. Your flathead frineds would probably have a better input.

But I would venture to say that with the work you have done it will probably need some time to bleed out air bubbles, etc. And that might have an impact.

But I would be much less suspicious of an older engine overheating than something newly rebuilt.