Is this gauge in pic pegged?
 

I'm trying to figure out why my new replacement temp gauge from LMC is not working. They are a little different than stock but come with good directions. They are supposed to be more accurate than factory gauge. Anyway I read on here that if I want to test why it's not working the first and easyiest thing to do is take the green wire off the sensor and ground it and it should peg to the right. Here's a pic of what happens when I grounded the green wire. It moved far right but I'm not sure i would consider it pegged. What do you guys think?

Re: Is this gauge in pic pegged?
 

This is far as the gauge ever moves when everything is hooked up and i drive it,I can feel the thermostat open up after about ten minutes its a 195 thermostat.

Re: Is this gauge in pic pegged?
 

When I turn on the truck on cold the needle goes all the way left.

Re: Is this gauge in pic pegged?
 

No takers?

Re: Is this gauge in pic pegged?
 

Do you have the ceramic resistor installed on the back of the gauge? I am not 100% sure if all of the aftermarket gauges require it. Make sure you find out if it is needed or not.

The factory gauges need that resistor but some aftermarkets do not. It is possible that you have a resistor that is not needed.

Grounding the green wire is not a good way to test your temp gauge and will cause it to fail if you are not careful. I would not consider it pegged in your photo. Do you have the correct sending unit installed in the engine?


At normal operating temp, the gauge should read a little higher than that.

If you need any further help, just ask. If you need parts, just ask.

Take care,
Tom

Re: Is this gauge in pic pegged?
 

Thanks for responding t-bone, the instructions said not to put that resistor on the back so I did not. I will try to find another way to test it since you said not to ground it. May be tricky since these new lmc gauges are different than the old ones.

Re: Is this gauge in pic pegged?
 

I don't know if the sending units are correct or not they were in there when I bought it a couple months ago. I have two because I had a TCS from factory. Both senders i hook it up to read the same. The guy had the green wire hooked up to the sender in the head. I think that was the one for the TCS. Maybe someone swapped out the one in the thermostat housing with the wrong one i dunno.

Re: Is this gauge in pic pegged?
 

When I tested the sender in boiling water with a ohm meter it was off by about 50 ohms. In electronics class the teacher said its ok for testing to be off a little but maybe 50 ohms is too much. Wish I was in school right now but I'm off for the summer other than welding class.

Re: Is this gauge in pic pegged?
 

I am not familiar with the LMC gauges so I would follow there directions to be safe. If you think the gauge is the problem then send it back for an exchange and see what happens. On a factory gauge, you must use the resistor on the back. When you ground the green wire, you send a straight 12V (battery voltage) to the gauge. It is OK for a split second to check needle movement but should never be held on for more than a second. The sending unit is designed to as a heat sensitive resistor. The lower the temp, the more resistance. With more resistance, the gauge will read low. When the temp rises, the resistance will decrease and allow more voltage to the gauge causing the needle to move up.

I hope this is making since. Do you have an ohm meter to check resistance values?

Just read your last post. I will have to find my chart with resistance values. I don't want to guess at this and steer you in the wrong direction.

Re: Is this gauge in pic pegged?
 

If mine were that high it would be overheating. I've never seen mine go that high and mine starts on the first line.

Re: Is this gauge in pic pegged?
 

Yea that makes sense. I wonder why the gauge wont peg. Maybe it is just a bad gauge. I wonder if the wire could be bad and be holding resistance? I did clean the wire pretty good when the cluster was off, maybe I broke it or it was already bad. It was covered in oil from a bad valve cover gasket. The old gauge would start cold and work its way up to almost red but I read that was a common problem and that's why a replaced the gauge.

Re: Is this gauge in pic pegged?
 

Airspeed, it is only that high when I grounded the green wire to test the gauge.

Re: Is this gauge in pic pegged?
 

I have an idea to run a different wire from the sender straight to a post on the gauge and see if the gauge reads right. I'm not sure if that's a good idea or not. Or even which post I would run it to. I don't think ohm testing the wire would work because its not enough power to show resistance. Maybe I can check voltage between ground and green if I'm quick. I'm not sure what I should do I'm gonna try to research some more. If anyone thinks any of these ideas are good or bad please let me know.

Re: Is this gauge in pic pegged?
 

I hate it when I see dead end threads where people ask for help and then don't say what the problem was so just in case anybody has this happen in the future and comes across this thread,

the problem was incorrect installation of the new gauge, I had grounded the gauge to the dash case which bypasse the internal resister that the lmc gauge has, after repositioning the gauge it now works great!

Re: Is this gauge in pic pegged?
 

Your gauge may not be pegging out due to resistance in the wire. OHM check the wire from the sending unit to the gauge and see what you get. You could also ground out the wire and take a voltage reading at the gauge and see what it is getting. IMHO the needle should be pegged with 12v. On a side note I have never heard of a gauge blowing form getting 12v, especially on a 12v system! What sense would that make, your truck overheats and sender sends 12v to the guage and it fails so you have no indication.

Re: Is this gauge in pic pegged?
 

My stock gage and those in my past trucks have always run exactly like the one in post #2...
...just shy of GM's normal operating range on the gage. I run a 195° thermostat with correct shroud,
a clean block and a good radiator.

Re: Is this gauge in pic pegged?
 

Wouldn't a colder temp reading on the gauge indicate there was TOO MUCH resistance? If so, how did the incorrect ground / bypass of the resistor cause it to read colder than it should?

(BTW - my gauge is reading just like yours was in post #2, even when warmed up. I'm on my 2nd sender. My gauge DOES peg all the way to the right when I ground the sender wire)

Re: Is this gauge in pic pegged?
 

This is the normal reading of the gauge.:chevy:

http://67-72chevytrucks.com/vboard/a...1&d=1432606668

The first picture shows a over heating motor.

Re: Is this gauge in pic pegged?
 

Lots More Crap (from China). Kinda says it all.

Re: Is this gauge in pic pegged?
 

There are several other threads regarding temp gauges right now. Originally the temp gauge would have read a little higher on ther scale than what yours shows. Logic would say if you used yours as is, if the truck overheats, the gauge will still only register mid scale. IMO you dont have the correct sending unit. Its the one in the head for the gauage. I bought one off ebay and it works great. At normal operating temp its just to the right of the left line, a little farter right than yours. Off and after sitting overnight, It is all the way to the left. It was pricey at $37, but works.

Someone posted one from classic part for $8/$9, but i dont have any experience with it.

Re: Is this gauge in pic pegged?
 

Heres the one i bought

http://m.ebay.com/itm/261580097652?r...24&_mwBanner=1

Re: Is this gauge in pic pegged?
 

Classic parts.com lists one as pn 53-811. I have no experience with it.

Re: Is this gauge in pic pegged?
 

:agree: That's where mine registers too, after warmed - especially when idle at stop lights etc...

Cold |---| Warm(Normal)/Hot |---------| Overheat |---|

Re: Is this gauge in pic pegged?
 

Lol, this thread is so old! Problem was solved a long time ago as I posted above. The gauge works fine now, I just installed it wrong and one of posts touched the case. I already stated the problem and that it was fixed but somehow this thread just refuses to die.:lol:

Re: Is this gauge in pic pegged?
 

To answer your question though century yes. Bypass may have been the wrong word but when the post touched the case the gauge would not peg. Somehow that increased resistance (Im guessing) and would not let me peg the gauge when I grounded the green sensor wire. Once I repositioned the gauge with the post off the case I could peg it and the thermostat opens up when the gauge is close to vertical. It's more like the gauge on my 95 c1500 now. Just so were clear too this is not an original style gauge it's a different style from LMC with no external resister. The resister on these is internal. Maybe you guys have different gauges or something but I like mine to read about 200 when verticle just like my 95. So now that I have that and that the guage pegs when I ground the sensor wire I'm happy with this one and prefer it wether it works like an original or not. Hopefully this thread can die now.:lol: if it helps somebody in the future that's cool too but I think for the most part it's just a record of a stupid intallation mistake I made that no one is likely to duplicate.:exit: