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broncridingirl 08-26-2011 09:35 AM

temp gauge troubleshoot
 
I just replaced my fuel and temperature gauges with Ruggid Ridge set and the temp sending unit also. The fuel gauge is working, but the temp gauge is pegged to the left and hasn't moved at all. I've done the troubleshoot that John Strenk recommends and am pretty sure that my grounds are good. I get a reading of about 91 ohms across the new temp gauge and am wondering what this high of a reading means. Any ideas?
I had a heck of a time finding the right temp sending unit and ended up using a bushing to make the one that was too small turn into a 3/8" pipe thread. I bled the air out, so I'm pretty sure it has good contact with the coolant, and temp sending wire at the temp sender has power to it. I'm a little unsure from John's instructions how to check my temp sending unit in place, is this doable?

Thanks!

John Strenk 08-26-2011 10:15 AM

91 Ohms is a little high for an OEM meter. Now replacement temp meter resistance can be anything depending upon design. The reason for this is that the inside of the meter has a bi-metallic movement that moves when heated. The heat is supplied by a resistance wire wrapped around the bi-metallic bar that measures 21 ohms. As the wire heats up, the more the bi-metallic bar moves. A new meter may have a more sensitive movement and only need a 91 ohm heater.
This is why they usually recommend replacing both the fuel gauge and the temp at the same time by the same manufacturer. Does your fuel meter also measure 91 ohms across the terminals?

You should be able to read the resistance of the sending unit with an ohm meter when it's in the block.
It's probably the best way to check the sending unit.

Disconnect the ignition coil
Turn the ignition ON
Check to see if Temp Meter is pinned, if pinned, turn ignition off.
Take the wire off the sending unit.
Turn ignition ON if turned Off
Check to see if the meter is still pinned , if pinned, turn ignition off
IF it still pins you have a short some place.
______Try take the wire off the back of the temp meter and see if it still pins.
Still pinned then you hooked something up wrong or there is a problem with the meter


A common problem is to have the meter rotated a bit in the housing and short out one of the terminals.
http://civilianjeep.info/Guage%20web...ssalighned.jpg


To check Resistance of Temp Sending Unit
Ground one lead of the DVM to the block.
Touch the other lead to the terminal on top of the sending unit.

Resistance Test:

73 ohms Cold - Test when engine is slightly warm. A stone cold engine will read 400 ohms
36 ohms Beginning of Band
13 ohms End of Band
9 ohms Hot
Resistance across OEM meter terminals= 21 ohms


To make the temp meter peg you will need to have near 0 ohms.

Btowntaz 08-26-2011 10:17 AM

Get a mechanical temp gauge and be done with it! Haha Installed a secondary temp mech. gauge and love it.

Are you sure the gauge is wrong? Have you ever worked on your thermostat? Reason I ask, I had a problem with temps and was going to change out the thermostat, to my surprise, I didn't have one installed! Shot in the dark.

broncridingirl 08-26-2011 10:40 AM

Thanks! I will give your troubleshoot another try when I get home tonight. I'm thinking it might be shorted somehow. I'm hoping I've not burned it up by driving it the way it is...

Just got a new thermostat when I got my radiator flushed last week, so hopefully thats not the problem.

John Strenk 08-26-2011 10:50 AM

Remove all the wires on the temp gauge and check if the "S" terminal is shorted to ground with an ohm meter.

broncridingirl 08-26-2011 08:22 PM

Now I have been on a search for my ignition coil... and I can't find it. Is it possible that it has had some upgrade and is part of my distributor?

John Strenk 08-27-2011 05:15 AM

Quote:

Originally Posted by broncridingirl (Post 12083631)
Now I have been on a search for my ignition coil... and I can't find it. Is it possible that it has had some upgrade and is part of my distributor?

Yes, It could be an HEI distributor and in that case, don't worry about disconnecting it.

The HEI distributor like a DUI have the coil inside the distributor cap.

http://www.acmejeepparts.com/categor...stributors.jpg

got a picture of the passenger side of the engine?

John Strenk 08-27-2011 05:40 AM

Oh wait, I just saw you have a GM 151 engine.

It probably has a GM ignition system so don't worry about disconnecting it.

broncridingirl 08-28-2011 02:10 PM

Going back through the whole troubleshoot procedure, and using a light tester this time, I find that the temperature sending wire is a solid light, not a flashing light. Now what? I tested the gauges and they all seem to be in the right ballpark for resistance. Thanks for your help!!!

broncridingirl 08-28-2011 02:14 PM

I just checked with the test light from A to ground on the temp gauge, and it doesn't flash, but the light is dim. Same goes for the fuel A to ground. Is it not flashing because I've got rugged ridge gauges that do something a little different with the resistors?

turbogus 08-31-2011 10:58 AM

Quote:

Originally Posted by John Strenk (Post 12081324)
Remove all the wires on the temp gauge and check if the "S" terminal is shorted to ground with an ohm meter.

Hi John, Seems of late I may be having temp sender issues with my '78 CJ5 360. During hot days in western Oregon 90+ My mechanical gauge can read as high as 210 when I'm wheeling while the cluster gauge is pegged Hot. The mechanical gauge sender is inserted into a water jacket on the intake manifold opposite of the cluster temp gauge sender. I replaced the non functioning cluster temp gauge sender with an Echlin and reading was nominal for about 8 months (from cooler winter temperatures to the following summer) but at 180 indicated on the mechanical gauge the cluster gauge was pegged at Hot, same this again this time only at 210, is 210 really Hot?

John Strenk 09-01-2011 02:38 AM

I would say 210*F is not really that hot.

However you probably should check your temp gauge and sending unit. See if you can borrow a ohm meter and read the resistance of the sending unit.

73 ohms Cold - Test when engine is slightly warm. A stone cold engine will read 400 ohms
36 ohms Beginning of Band
13 ohms End of Band
9 ohms Hot

If you are reading less than 9 Ohms then your sending unit thinks the engine is HOT.
If it's not reading 9 Ohms but less then something is shorting out.

IF it's reading around 20 ohms then there is something wrong with the gauge. What could happen is that the regulator is not working because of a bad ground. this will make the temp sensor overly sensitive and peg at lower temps. This is because instead of getting a pulse of current, it's getting constant current and over heating the gauge. Simplest test is to get a test light and see if the "A" terminal on the fuel gauge is working. If the "A" terminal is flashing and you are reading 20 Ohms on the sensor then you have a gauge problem. You might be able to adjust it but that is pretty far out of range.

broncridingirl 09-01-2011 09:41 AM

So I'm having basically this same pegging problem now. I realized that ******* me had the temp gauge hooked up incorrectly, following the diagram that they sent, not I and S marks on the gauge. I also discovered that my temp sending unit was shorted. Maybe this was caused by being hooked up with the sending wire from the I to the sending unit, instead of S to the sending unit? I've since replaced my temp sending unit and fixed where the wires hook up. Now the gauge when hooked up to the sending unit is pinned hot. When unhooked it is pinned cold. The resistance across I-S is about 28 ohms, same for the fuel gauge. So, my question is, did I fry my gauge when I had it hooked up wrong? How do I confirm this? Also, my guages don't flash the test light, they have soild light. Is this because there is something wrong with them, or could it be because they are aftermarket and function a little different?
Thanks for your help. This thing is driving me NUTZ!

John Strenk 09-01-2011 10:40 AM

Quote:

Originally Posted by broncridingirl (Post 12089959)
I just checked with the test light from A to ground on the temp gauge, and it doesn't flash, but the light is dim. Same goes for the fuel A to ground. Is it not flashing because I've got rugged ridge gauges that do something a little different with the resistors?

Could be, resistors won't flash but you need to replace both gauges at the same time. Usually they don't have 3 posts on the fuel gauge.

Some of the 2 post gauges just use resistors to control the current through the gauges. It's OK for for environments but doesn't compensate for changes in voltage or temperature.

John Strenk 09-01-2011 10:45 AM

Quote:

Originally Posted by broncridingirl (Post 12089959)
I just checked with the test light from A to ground on the temp gauge, and it doesn't flash, but the light is dim. Same goes for the fuel A to ground. Is it not flashing because I've got rugged ridge gauges that do something a little different with the resistors?



Quote:

Originally Posted by broncridingirl (Post 12109158)
So I'm having basically this same pegging problem now. I realized that ******* me had the temp gauge hooked up incorrectly, following the diagram that they sent, not I and S marks on the gauge.

I also discovered that my temp sending unit was shorted. Maybe this was caused by being hooked up with the sending wire from the I to the sending unit, instead of S to the sending unit? I've since replaced my temp sending unit and fixed where the wires hook up.

Now the gauge when hooked up to the sending unit is pinned hot. When unhooked it is pinned cold. The resistance across I-S is about 28 ohms, same for the fuel gauge.


So, my question is, did I fry my gauge when I had it hooked up wrong? How do I confirm this? Also, my guages don't flash the test light, they have soild light. Is this because there is something wrong with them, or could it be because they are aftermarket and function a little different?
Thanks for your help. This thing is driving me NUTZ!

Since you are talking about an "I", "A" and "S" terminals in your posts. I have to "assume" you have a 3 post fuel gauge. Usally these have an internal regulator and the case of the gauge needs to be grounded. If not grounded then there is no regulation and you CAN burn out your gauges.

But not necessarily so. your resistance reading are pretty good so it didn't burn up. yeah you can burn things up or you might be lucky and they will just run really hot. So, do you feel lucky?

Can you scan the directions and post them or email me the scans? Maybe a good photograph would work. Also a picture of the back of the gauges if you can.

There are two different typed of replacement gauges, those with regulators and those with resistors. I need to find out which you have.
Those with regulators need to be grounded. those with resistors don't seem to need to be grounded.


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