Engine temperature gauge has no power to sending unit.

[CDLong]

Thanks for the heads up Gary.

[CDLong]

Would I be better of gettin' 1200 grit paper?

[CDLong]

Gary Lewis wrote

Yep, I use an eraser as well.  But stay away from the end of the trace as you might snag it and peel the copper off the flex.

Ok, I have 15 pics of the cluster. I don't see any issues, but I don't really know what to look for other than the ribbon being broken. Just to make sure I'm clear,I should clean the entire ribbom with a soft eraser? If you need a different photo, just let me know of what.

[Gary Lewis]

Don't clean the whole ribbon.  All you are concerned about is two places - where the connector goes in and where the temp gauge nut screws on.  If either place is corroded you may not get the gauge to work.

BUT, be very careful in taking the nuts off the temp gauge as if the stud turns it'll ruin the gauge.  I'd use soft-jawed pliers to hold it while breaking the nut loose.  Then pull that nut off and clean the ribbon where the nut goes.  Do each nut in turn.

As for where the plug goes, sand or run the eraser away from the end of the ribbon so you don't catch it and pull it off the backing.

[FuzzFace2]

A little late sorry
I would say before you go putting it back in is to test it.
You should be able to tell what the 12 volt into the IVR is and put 12 volt to it.
You should also be able to tell what the ground is for the ribbon and ground that.

You can now take your test light and check for power into the IVR = on all the time.
Then check for power out = blinking.

Now follow the out put to each gauge or just the temp gauge as that is the one not working and test for power in = blinking.
Now test to output of the gauge = blinking (no blinking either bad connection or bad gauge.
I would follow the ribbon all the way to the plug and test for power there for each gauge = blinking.

Some where along the path for the temp gauge power is not going thru.
Dave ----

[CDLong]

Thanks Dave. I was figuring on testing it.

[ArdWrknTrk]

If your fuel gauge and oil pressure work you don't have any problem with the Instrument Cluster Voltage Regulator.

You can check for continuity through the gauge in the trace on the mylar circuit board and you can check continuity on the wire to the sender by grounding the little right angle connector to the engine, then checking for continuity to ground from the big multi circuit plug that goes into the back of the cluster.

[CDLong]

FuzzFace2 wrote

A little late sorry
I would say before you go putting it back in is to test it.
You should be able to tell what the 12 volt into the IVR is and put 12 volt to it.
You should also be able to tell what the ground is for the ribbon and ground that.

You can now take your test light and check for power into the IVR = on all the time.
Then check for power out = blinking.

Now follow the out put to each gauge or just the temp gauge as that is the one not working and test for power in = blinking.
Now test to output of the gauge = blinking (no blinking either bad connection or bad gauge.
I would follow the ribbon all the way to the plug and test for power there for each gauge = blinking.

Some where along the path for the temp gauge power is not going thru.
Dave ----

My other gauges are working correctly. I appreciate your help. I assume I can usepower from the battery or should I get a 12V bench tester?

[FuzzFace2]

I would use a battery as we all have one of them around.
I dont have a bench top power supply but if you do and it puts out 12 volts then that can be used for testing.

If me I think I would put power to the IVR as we know that works as the other 2 gauges work.
Then test that power (blinking) out of the IVR to the temp gauge input is good and then the output of the gauge.

If you have power in & out of the gauge you will need to trace the board out of the gauge to the plug as it has to be failing some where?

If that checks out then you will need to test the wire from the plug to the sender in the engine bay as it may be open.
Dave ----

[Gary Lewis]

Be careful as the gauges are really 6v gauges, as Jim said.  The ICVR just chops the voltage until the average is about 6v, and since it is really just feeding a heating element in the gauge the chopped DC doesn't matter.

But if you put 12v to the gauge you could burn out the heating element.  And it'll peg in a hurry.  In my testing 5.4V pure DC is about right to bring the gauges to the top mark.

[CDLong]

FuzzFace2 wrote

I would use a battery as we all have one of them around.
I dont have a bench top power supply but if you do and it puts out 12 volts then that can be used for testing.

If me I think I would put power to the IVR as we know that works as the other 2 gauges work.
Then test that power (blinking) out of the IVR to the temp gauge input is good and then the output of the gauge.

If you have power in & out of the gauge you will need to trace the board out of the gauge to the plug as it has to be failing some where?

If that checks out then you will need to test the wire from the plug to the sender in the engine bay as it may be open.
Dave ----

Thanks Dave, I was told that because my other gauges work, it's probably in the wiring.

[CDLong]

Gary Lewis wrote

Be careful as the gauges are really 6v gauges, as Jim said.  The ICVR just chops the voltage until the average is about 6v, and since it is really just feeding a heating element in the gauge the chopped DC doesn't matter.

But if you put 12v to the gauge you could burn out the heating element.  And it'll peg in a hurry.  In my testing 5.4V pure DC is about right to bring the gauges to the top mark.

 I guess I could use a 6-volt lantern battery? Gary, what do you use to obtain 5.4 volts?

[Gary Lewis]

I use a lab power supply that is adjustable.  But you could use a 6v battery for testing.  However, you really shouldn't need to do that.  As has been explained, if you put a test light where the sending unit is you should see the light flash if the wiring is good.  (The flashing is because the ICVR is just a chopper, not a voltage regulator.

And if it is flashing then grounding the wire should send the gauge to full scale pretty quickly when the key is on.

I replaced the wonky ICVR with an adjustable voltage regulator, as you can see on the page at Documentation/Electrical/ICVR.  However, if your other gauges are working correctly then it isn't the ICVR.

[CDLong]

Gary Lewis wrote

I use a lab power supply that is adjustable.  But you could use a 6v battery for testing.  However, you really shouldn't need to do that.  As has been explained, if you put a test light where the sending unit is you should see the light flash if the wiring is good.  (The flashing is because the ICVR is just a chopper, not a voltage regulator.

And if it is flashing then grounding the wire should send the gauge to full scale pretty quickly when the key is on.

I replaced the wonky ICVR with an adjustable voltage regulator, as you can see on the page at Documentation/Electrical/ICVR.  However, if your other gauges are working correctly then it isn't the ICVR.

I'm don't have a lot of electrical knowledge. The cluster is out of the truck, I need to replace the shift. Could I put 12 volts DC to the red & white wire in the plug that attaches to the cluster and check the connector that attaches to the sending unit for 12V?

[Gary Lewis]

If I understand what you are asking, then yes.  I think you are saying that you'll put 12v on the R/W wire in the dash at C208A, with the cluster disconnected, and check at the sending unit for 12v.  That will work.  BUT, make sure the wire isn't on the sending unit your may mess it up.

[ArdWrknTrk]

Would probably be better to indicate resistance than voltage, as that's what the gauge is doing.

[Gary Lewis]

Right. It would be easy to put the connector on the sender and read from the red/white wire to ground. The sender should be between 12 and 72 ohms, and probably close to 72.

[CDLong]

Gary Lewis wrote

If I understand what you are asking, then yes.  I think you are saying that you'll put 12v on the R/W wire in the dash at C208A, with the cluster disconnected, and check at the sending unit for 12v.  That will work.  BUT, make sure the wire isn't on the sending unit your may mess it up.

Yes, you understood me correctly, but I will be checking the resistance as Jim has suggested.

[CDLong]

Thanks Jim, I'll check the resistance in the wire.

[CDLong]

Gary Lewis wrote

Right. It would be easy to put the connector on the sender and read from the red/white wire to ground. The sender should be between 12 and 72 ohms, and probably close to 72.

Thanks Gary. even I can understand how to do this.