Instrument cluster testing

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mopowers

mopowers

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Is there and easy way to test a gauge cluster out of the car? Specifically, I've traced a problematic fuel gauge and water temp gauge to the cluster.

Is there and easy way to test an instrument cluster voltage regulator??
 
i would like to know as well im going through the same thing...question for you does the red and black wire on the left side of the dash run to the voltage gauge
 
Sure is.

1..........Identify what problems you can before you start. Generally, this includes loose/ broken harness connector pins, contact finger connections for the IVR, and stud nut connections at the gauges. Loosen / tighten the stud nuts to scrub them. Do the same thing with all PC board to cluster ground screws.

2...........Attach a ground pigtail for your testing, but also later, to bolt to the dash frame or column support.

3...........Identify the proper harness connector pins for 12V in, and for each sender connection


4..........Go to RadShack (or order online, Mouser, Digikey, etc) some test resistors, or if you have the tank sender out and it works, and an accurate multimeter, you can use the tank sender

Get some resistors, at least 1/2 to 1 watt. You can parallel resistors to increase wattage. For example, for 1/2 scale, you can buy four 100 ohm, 1/2 watt and wire all 4 in parallel. This gives you a 25 ohm, 2 watt resistor.

For full scale (hot or full) you need 10-13 ohms, for 1/2 scale you need 23-25 ohms, and for the low end (cold or empty) you need 73--75 ohms.

You hook a test resistor from the appropriate sender connection to ground, you apply 12V to the proper pin, and wait a minute for the gauge to stabilize.

==========================================================================

Another thing you can do is to yank the IVR out and hook 3V (two flashlight cells in series) to the gauges directly. This should result in full scale reading, and both gauges should read the same. See the photo at the bottom of the page

If you look at the PC board, two of the gauge studs are hooked together. If you hook the battery to the two opposite studs of the two gauges, this results in about 1/8 scale

The top photo is with two gauge units in series across 3 volts, bottom is in parallel. Notice that both read the same

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If you have a ralley cluster, or an older car where the IVR is built inside the fuel gauge, this gets a bit more complicated. Notice that the fuel gauge has THREE terminals. One of these is the 12 "into" the IVR, one is the 5V out of the IVR going to the other gauges, and the third is the sender terminal for the fuel gauge.

For testing with a 3V battery you want to be certain you identify the two gauge terminals of the three
 

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This is my 67 cluster. It had damaged and broken connector pins. I ended up abandoning the original connector, soldering pigtails to the board traces, and using Molex style connectors from RadShack. The IVR connector fingers did not make contact with the board traces, and I soldered them across. Not visible is loose stud nuts. The wire up by the speedo is the added ground pigtail. Do yourself a favor and buy an aftermarket solid state IVR
 

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Some photos of the clusters In the marked photo,

12V is switched 12V from the ignition key feeding the input of the gauge VR

At the bottom right, "5V" is the trace feeding the 5V output of the VR over to the temp and oil gauges on that board trace

FS is to the fuel sender

TS is to the temp sender

OS is to the oil sender

RT is the green dash right turn indicator

So first hook a battery from 12V to cluster ground

Hook your test resistors to the sender terminals to ground, one at a time.

Depending on which test resistor you use should move the gauge. All three gauges should read the same on respective resistors, IE 23--25 ohms on each gauge should give you 1/2 scale. Allow a minute for the gauges to warm up and stabilize.

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)


Another source shows as much as 78 ohms for empty, 21 for mid and 10 for full
 

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Not to thread jack buit I've got skin in this game too, LOL Headed to radio shack to see what kind of resistors they have.
Luke
 
iw378 said:
Not to thread jack buit I've got skin in this game too, LOL Headed to radio shack to see what kind of resistors they have.
Luke
Click to expand...

'S why I posted the last photos here, LOL
 
Okay. I hooked it all up on the work bench. I used the 23 ohm resistor for half scale to check the gauge. It slowly went to full. Not good I assume. I then took and hooked up a sending unit to it and with the float down it still went slowly to full. When I moved the float manually it went to full faster. I then checked the voltage at the FS stud and the oil and temp stud and read 12 volts (should be 5)
? So i guess the VR in my fuel gauge is shot. The reason the po had aftermarket gauges in it. LOL can my fuel gauge be repaired?
Luke
 
When I checked it with the 73 ohm it still went to full but just really slow.
Luke
 
iw378 said:
? So i guess the VR in my fuel gauge is shot. The reason the po had aftermarket gauges in it. LOL can my fuel gauge be repaired?
Luke
Click to expand...

Sure sounds like it. If you google around there's a site showing how to DIY the IVR in the fuel gauge. What this basically involves is to carefully cut/ remove enough of the guts of the IVR to render it "safe," then wire in an external IVR and run the 5V output to that stud with the black cover which I marked "5V" This will feed 5V then, to all three gauges.

Here we go:

http://rt-eng.com/rte/index.php/RTE_Limiter_Faq
 
67Dart273 said:
Sure sounds like it. If you google around there's a site showing how to DIY the IVR in the fuel gauge. What this basically involves is to carefully cut/ remove enough of the guts of the IVR to render it "safe," then wire in an external IVR and run the 5V output to that stud with the black cover which I marked "5V" This will feed 5V then, to all three gauges.

Here we go:

http://rt-eng.com/rte/index.php/RTE_Limiter_Faq
Click to expand...
That looks like some delicate work. I'm an Ironworker for pete's sake. LOL
When I did the checks the 5 volt output stud was putting out 12 so do you think that the other 2 gauges got toasted ? How can I check them without 5 volts. If I solder a bunch of brake light bulbs together to cut 12 v down to 5
and use the resistors to check the other 2 gauges do you think that would work ??
 
Without "being there" or having a fuel gauge to dissect, there are some caveats..........but look above in this thread.............if you put 3V directly across one gauge, it should read close to full scale as shown in one of the photos near the top of the thread.

The trick would be to "get into" the fuel gauge and cut out the bad IVR so it doesn't short or cause problems for testing or replacement.

So far as the other two gauges, if you simply remove the nut on the fuel gauge where the black plastic cap is, that will electrically isolate the other two gauges.

For example look at the photo below with the added black markings

Remove the black plastic as shown and the nut below it

Hook 2 flashlight batteries in series (3 volts) to the two marked "3v oil" to check the oil gauge, leave them on for 30 sec. or so. The gauges should go "not quite" to full but should not peg

Likewise to check the temp gauge, apply your 3V to the two marked "T"

You cannot check the fuel until you successfully get the old IVR disconnected.

There are folks who rebuild them. I believe "Redfish" does that work.
 

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Just check across the gauge posts with a ohms meter. You're looking for 20 ohms +/- .5 That doesn't prove the gauge is accurate but at least proves its still alive.
 
68coupe said:
Before you guys go to ordering high-priced voltage regulators, you need to check this little unit. Input up to 35 volts, output 5 volts.

http://www.radioshack.com/product/index.jsp?productId=2062599

You also need a filter condenser to go with it. I'll look later (tomorrow) to see just exactly which one to purchase.

Better yet, check this out.

http://www.moparts.org/Tech/Archive/elec/11.html
Click to expand...


Tell ya. I'm fully capable of building a regulator. But I've bought enough parts from RS that were FAILED "right out of the box" that I sure as hell am not about to use one for a cluster IVR
 
Cool! That's good to know, Redfish. I didn't know what that value is (20 ohms). That will also tell if the gauge unit is open, which I would imagine is what usually is the problem, other than the sending units. Thanks
 
I'm out. I'll start my own thread so the OP gets the info he needs . My problem may be different than his.
Luke
 
68coupe said:
Cool! That's good to know, Redfish. I didn't know what that value is (20 ohms). That will also tell if the gauge unit is open, which I would imagine is what usually is the problem, other than the sending units. Thanks
Click to expand...

20 ohms is a good sign but lots of different conditions are possible.
The wire insulation in a gauge will get crunchy with carbon buildup then crack. A tiny speck falls off allowing the winding to short to the bimetal.
In this case one gauge post will have some portion of 20 ohms resistance to the gauge can. The other post would have the balance of 20 ohms resistance to the gauge can.
 
68coupe said:
whatever..............
Click to expand...

It's not "whatever." All I'm saying is, if you are going to build a regulator that might destroy hard to replace gauges, buy quality parts from Digikey or Mouser. Do not buy them from RadioSh##
 
There isn't consistent quality anywhere. DigiKey offers these regulators from several mfgrs. Some will supply 4.86 average volts. I've found only 1 brand that consistently supplies 4.99 to 5.07 volts. Even so, the novice can over stress /bend the legs and ruin them, or linger with a soldering iron overheat and ruin them.
If you're not afraid of shock hazards you could go through your home opening DVD players,TVs, everything, and never find one of these regulators with its legs spread like a dime store *****. They aren't designed for that.
Yet those who did bend those legs once without killing the regulator posts pictures on the web and says "Here's what to do". . Its all just more horse chit in the stable that no one can shovel up. I dont even try. Bend the little thingy
 
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