Help me test my gauge UPDATE Gauge is working

[k5ryder]

Below is a picture of my temp gauge. It does not work. I've tried grounding the wire that connects to the temp sensor or sending unit (whichever it is) and I get nothing. Is there anyway I can test it pulled out like this? Also my clock doesn't work. Do these two gauges side by side not working mean anything?

 

[dyeager535]

You got the cluster pulled too? Figure out which stud gets 12V, and which is ground by tracing the circuit card on the back of the cluster. Also note which is the "signal" (to sending unit) stud. Hook the + and - studs up to a battery (correct polarity of course) and see what happens. Gauge should peg one direction. Then take another wire, and connect the signal stud to the ground stud. Gauge should peg the other direction.

If the gauge does not respond as noted, the gauge is faulty, or your temp wiring is faulty/not making good contact.

That simple. Fuel, temp, and oil pressure operate the same way. Voltmeter obviously just uses the + and - cluster feeds to display voltage.

Clock not working could be the clock, or power/ground to it. Could be related, but probably not...I think all gauges on that side of the cluster share the same +/-, so you'd most likely have other gauges that didn't work in the same manner if it was a larger problem. The clip in "sockets" in the cluster don't always make good contact with the gauge studs, or the copper they touch.

This is why I hard wired my cluster.

 

[k5ryder]

I do not have the entire cluster pulled. I just pulled off what I had to to get the gauge out. When I get home I will try to figure out which on is negative and which is positive.

 

[dyeager535]

Need to have a multimeter anyway, so the easy way without pulling the cluster is to turn the key to run. Set meter to continuity. Probe each of the three "clips" on the cluster housing until you find ground. Probe the other two for voltage. Once you've got + and - figured out (doesn't hurt to use a sharpie to pen those markings onto the gauge body) figured out, check continuity from the third clip to the termination of your temperature sensor wire at the block.

If all three of those check out (any failure of above test means the gauge isn't likely the problem) re-insert gauge and see if it works.

Last resort will be to wire the gauge itself directly to battery +/- source, and ground the wire on the sending unit stud to confirm the gauge is dead.

 

[k5ryder]

Help me test my gauge

I do not have a
Multimeter but I do have a test light. Before I do anything else I'm going to check to see if there is even a thermostat in the housing.

 

[dyeager535]

Shouldn't need to check for a thermostat. If the upper hose is hot to the touch after running for a bit, you have one. If the hoses aren't hot, then agree, pull the housing off and check.

A cheapy multimeter from Harborfreight is about $18. Buy one if you have a thermostat. Test light doesn't work for checking the gauges. You'll use it far more often than a test light, once you find its functionality.

 

[k5ryder]

Help me test my gauge

Ok, with my continuity my black probe is on the right side and my red is on the upper side and its beeping. I can't make it beep anymore then that.

 

[k5ryder]

I hooked 12 volts to the gauge and it started moving. Now what? And what is supposed to make it move down once the engine cools?

 

[dyeager535]

Sorry I didn't have time prior.

Continuity is used to test that whatever circuit you are working on, doesn't have any breaks in it...as in a broken wire, bad connector/connection, etc. Color of your probe doesn't matter what you touch to what...if you touch the two of them together, it will beep. You could use the continuity setting to check for ground. Hook one probe up to a known good ground on the truck (like a dash screw or threaded hole) and touch each of those "clips" in your picture with the other probe. When it beeps, you know which one is ground. If it doesn't beep, your ground to the body is probably the issue. You can test THAT ground by touching another spot on the body and making sure it beeps. You know you are grounded if that happens.

Once you establish which of the three is ground, then you should be able to switch the meter back over to DC, and using the same ground, probe the other two clips to see which is 12V with key in run.

Once you've got the +/- figured out, the final is continuity on the sender wire/clip. Take one probe, and using another wire that is long enough, connect it to the temp sender end of the wire. Then use the other probe, touch it to the clip that is not + or -. It should beep. If it does, every section of wire and connection between the two probes, is good...There are no breaks in the wire. You can THEN, when you take the probe off the engine bay side of the wire, ground that same probe (so one probe is connected to the cluster clip for instance, the other to ground), it does NOT beep. That means the wire jacket is intact, and the wire is not shorted to ground.

You can use a test light to check for + and - of course, but if the light is an LED (polarity specific, so will only light one way) it would be more useful in this case. You would only get the light to come on between the + and - with the key in run of course. But I don't want to muddy the waters, if you've got a multimeter now, then you should stick with that. The light is too limited/too much of a hassle for most things, IMO.

 

[dyeager535]

I hooked 12 volts to the gauge and it started moving. Now what? And what is supposed to make it move down once the engine cools?

Run the tests I described above on the cluster/wiring components...if the gauge is moving, it MIGHT be good. The cluster wiring on these trucks is always suspect, the connections are not real solid, not to mention the truck is how many years old?

 

[k5ryder]

Ok. I didn't think I did EXCATLY what you said but I got the gauge to move. It that good? Lol I'm gonna go try exactly what you just told me in the first paragraph

 

[k5ryder]

I found a good ground on the truck and touched the three clips to find my ground. Two of the clips beeped. I though only one would. So I have two grounds and one positive? And that mean I "though I hooked 12volts to the gauge correctly but I really connected 12v to two grounds on the gauge.


Edit. With the multimeter on DC I got 12v with the ignition on and the probes on the two clips that both beeped that I thought were both grounds(the top and the right one, also the ones I hooked 12v off my battery to the gauge and got movement). Idk which clip is the ground but I'm getting 12v

 

[dyeager535]

You MIGHT get a ground through the sending unit, although I think that is unlikely. Make sure it's disconnected in the engine bay.

You using a meter or something else? If meter, just use the DC Voltage setting, and figure out which is the + and -

 

[k5ryder]

I'm using a multimeter. I just unplugged the sending unit wire now I will go re check my DC test

 

[dyeager535]

Yep, just check the voltage first, make absolutely certain + and - are constant. Have to make sure you are eliminating any potential of bad contact when testing.

 

[k5ryder]

I really like this multimeter. I finally figured it out. The top is the negative and the right one is positive. Now what? You lost me on going the the sending unit with another wire.

 

[dyeager535]

Ok, so your + and -...you have 12V on the + when key is in run? If so, you know it's got power, and you tested ground too, so you know its good as well.

I don't know as I'd spend much time on the sending unit wire. If you have power and ground, and the gauge doesn't respond by pegging out, it's faulty. Don't take that wrong, double or triple check before throwing a part away, trust me.

But, to test the last clip/sending unit wiring, simply attach one of your multimeter probes (the black or red one, doesn't matter) to that clip in the cluster. You need to reach the engine side of the sending unit wire (where it connects at the sending unit in the head) with the OTHER probe, and check continuity. If it beeps, that is good.

Then, once that is done, leave one probe connected to the sending unit wiring (cluster or engine side of the wiring, doesn't matter) and touch the other probe to ground. If no beep, the wire is not shorted to ground.

 

[k5ryder]

But, to test the last clip/sending unit wiring, simply attach one of your multimeter probes (the black or red one, doesn't matter) to that clip in the cluster. You need to reach the engine side of the sending unit wire (where it connects at the sending unit in the head) with the OTHER probe, and check continuity. If it beeps, that is good.

I did this, connected one probe to the sending unit wire and one to the clip that wasn't positive or negative and got nothing

 

[dyeager535]

So it sounds like you have a sending unit wire problem, or the connector on the back of the instrument panel (IP) is screwed up.

Need to pull the cluster to get to that connector. I'm not aware of any other connectors in the temp sender wire, except probably the firewall connector. Up to you if you want to start at the most likely place (the IP connector) or at the firewall connector.

I'd loosen the IP (do not disconnect IP connector) and run a continuity test from the temp sender terminal on the IP connector to the temp sender clip where the gauge goes. If it passes that test (has continuity), remove the IP connector, and test the sender wire from the IP connector, to the engine bay again. When you get into the engine bay, take a quick look at the green wire, see if it's obviously cut. Save peeling back the wiring loom until you know whether or not the problem is in the cab.

 

[k5ryder]

So it sounds like you have a sending unit wire problem, or the connector on the back of the instrument panel (IP) is screwed up.

Need to pull the cluster to get to that connector. I'm not aware of any other connectors in the temp sender wire, except probably the firewall connector. Up to you if you want to start at the most likely place (the IP connector) or at the firewall connector.

I'd loosen the IP (do not disconnect IP connector) and run a continuity test from the temp sender terminal on the IP connector to the temp sender clip where the gauge goes. If it passes that test (has continuity), remove the IP connector, and test the sender wire from the IP connector, to the engine bay again. When you get into the engine bay, take a quick look at the green wire, see if it's obviously cut. Save peeling back the wiring loom until you know whether or not the problem is in the cab.

I'm probably gonna save this for the weekend. Also I need to pick up a buy a multimeter since I'm borrowing somebody's and I probably need my own. Check for some updates Friday night or Saturday. P.s. you've been loads of help. Thank you.