Test IVR

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Garys72Duster

Garys72Duster

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Can you test the IVR by putting 12 volts to the center ignition terminal, and see if you're getting 5 volts out of the other terminal? The negative is of course hooked to the very end one, which is connected to the outer case. Is this a good way to test it?
 
Can't speak to the terminals but assuming you have some load on the 5v side (small bulb) you would see jumping voltage (digital volt meter) if you have an analog meter you will see the needle go up and down but the needle should spend a lot of the time around 5 to 6 v

This all assumed it is an OEM mechanical unit. A newer electronic version would produce a steady voltage.
 
I think you will get a pulsing 12V, that averages to around 5V. An example is, if ON pulse time, is equal to OFF time, average would be 6V. The pulse is generated by a resistive heater on a bi-metalic contact, similar to a turn signal flasher unit.
 
The 1 I took out of this 72 Dart, doesn't show ANY voltage. And the fuel and temp gauges don't move, even when grounding the sensor wire. Seems like a common problem. Looks like it's the original unit, gee its only 48 years old! LOL. Amazon has em for 27.53.
 
By the way. You can take a 5v usb wall charger, or 5v usb cigerate lighter adapter. cut the cord and locate the red and black wires. Use some alligator clip leads and attach to the proper posts of the guages cluster. Now you have a test power source for your guages.
 
Dana67Dart said:
By the way. You can take a 5v usb wall charger, or 5v usb cigerate lighter adapter. cut the cord and locate the red and black wires. Use some alligator clip leads and attach to the proper posts of the guages cluster. Now you have a test power source for your guages.
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Thats a great idea! Check gauge function while I have the cluster out. Thanks!
 
Dana67Dart said:
Can't speak to the terminals but assuming you have some load on the 5v side (small bulb) you would see jumping voltage (digital volt meter) if you have an analog meter you will see the needle go up and down but the needle should spend a lot of the time around 5 to 6 v

This all assumed it is an OEM mechanical unit. A newer electronic version would produce a steady voltage.
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^^^This^^
Except IIRC one of the aftermarket versions also produces a pulsed output.
An oscilliscope would be best but an anolog meter will show it. I posted a video of in this post.
Gauge Cluster Issues/IVR

here is some more on bench testing
Bench testing rally gauges
 
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This is a loaded boat. "Test" suggests you verify the device is working properly and in this case verify it outputs the proper voltage and power

BUT THERE IS NO SPEC for that!!! Nowhere is there a spec for the IVR output. What this means example, is if you "happen" to get two gauges which are inaccurate to the same degree, then both fuel and temp gauges will register the same, and both will be "off" by the same degree, so "is it" the gauges or "is it" the IVR?

People throw 5V around but there is no basis for this. I've seen "50% duty cycle" but that would suggest the IVR produces the equivalent of 1/2 the battery, but when RUNNING that is 14V nominal, and means that the original pulse IVR "should" in theory output about 7V.

The point? Not sure there is an easy answer!!!!
 
Good points!
I basically agree.
The 5 volt number seems to come from old tech bulletins. For example this page
Thermal-Electric Gauges (Session 227) from the Master Technician's Service Conference

It doesn't say the IVR puts out an average of 5 Volts. It says the effect is the same as steady 5 Volts. Good info for testing the gage but not directly useful for verifying the IVR. When I tested the IVR in the '67 rally cluster you can see the voltmeter needle swings practicaly to full scale (8 Volts). I'm sure its not a true square wave or perfectly consistant in frequency.
I really need to get a 'scope...
 
That tech bulletin should be a sticky and required reading before you can post!
 
Mattax said:
Good points!
I basically agree.
The 5 volt number seems to come from old tech bulletins. For example this page
Thermal-Electric Gauges (Session 227) from the Master Technician's Service Conference

It doesn't say the IVR puts out an average of 5 Volts. It says the effect is the same as steady 5 Volts. Good info for testing the gage but not directly useful for verifying the IVR. When I tested the IVR in the '67 rally cluster you can see the voltmeter needle swings practicaly to full scale (8 Volts). I'm sure its not a true square wave or perfectly consistant in frequency.
I really need to get a 'scope...
Click to expand...

Thanks I prefer the pdf which is posted at MyMopar. Much easier to read and deal with and is the same document, "and there is a movie" LOL

http://www.mymopar.com/downloads/mtsc/227.pdf

 
Even a scope will show a very slow pulse rate of a trace line moving up and down and not a true pulse. This system is a very slow time constant thermal integration system. It was quite a bit of clever late 1950's engineering, but woefully obsolete now. The IVR regulators of this type fail in one of two ways the heater element burns out and you get no output or the contacts weld up and your gauges fry with a full 12 volts. An electronic type is the way to go. I suspect the widely known 7805 regulator scheme is a bit low in output voltage with the true original voltage somewhere between 5 and 6 volts.
 
As much as these are criticized, bear in mind that 'Ma' wasn't te only one. Ford used them extensively, I believe AMC might have as well. GM never used them to my knowledge.

My first experience with a bad IVR and pinned gauges was a 60 Ford Falcoon I had briefely in the fall/ winter of 67 before I joined the Navy
 
Hooked up the IVR this morning, and now it's showing a pulsating voltage coming out of the end terminal, opposite ground strap. So it seems to be working. Both gauges are now moving when the sensor wire is grounded.
 
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Now the amp meter is shooting all the way to discharge, when I turn the key to acc or run. So it has developed a short to ground downstream from the ignition switch. Maybe the factory welded splice? I know this factory elec system is a problem. Headlites are working fine with the key off, but something is taking alot of current when the key is in run position. It's not the meter, as I bypassed it, and it's still drawing too much current in run.
 
Garys72Duster said:
. Headlites are working fine with the key off, but something is taking alot of current when the key is in run position. It's not the meter, as I bypassed it, and it's still drawing too much current in run.
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How did you bypass the Ammeter?

If it is bypassed it should not be functional.

I would disconnect your ignition system and look for the current draw.
The ignition system should be about the only draw with the key on.
 
OK, I found it. The wiper switch/motor is the problem. Disconnected that, and now no more excessive current draw. I noticed it when the amp meter was hooked up, and I turned the ign sw on, it would jump all the way to the left-discharge. So I took the wires off the amp meter, and when I touched them together with the key on, it sparked alot. Also put a test bulb in series there, and it got really bright. So the wiper switch and motor is shorted to ground. Re hooked the wires to the ammeter, and it barely moves to the left now, when you turn the ign sw on. Had I left the key on, with the wiper motor hooked up, I'm sure we would be seeing some wires smoking! That's what I like about the ammeter, it gives you an immediate readout of which way the current is going, and how much. Whew, Dodged a bullet there!
 
Ok so your ammeter is not by passed with the MAD bypass or the like.

Glad you found your short without letting the smoke out if the wires.
 
Garys72Duster said:
OK, I found it. The wiper switch/motor is the problem. Disconnected that, and now no more excessive current draw. I noticed it when the amp meter was hooked up, and I turned the ign sw on, it would jump all the way to the left-discharge. So I took the wires off the amp meter, and when I touched them together with the key on, it sparked alot. Also put a test bulb in series there, and it got really bright. So the wiper switch and motor is shorted to ground. Re hooked the wires to the ammeter, and it barely moves to the left now, when you turn the ign sw on. Had I left the key on, with the wiper motor hooked up, I'm sure we would be seeing some wires smoking! That's what I like about the ammeter, it gives you an immediate readout of which way the current is going, and how much. Whew, Dodged a bullet there!
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Yes it can tell you things that a voltmeter can't. Good job.
Try not to play with sparking those wires too much.
Putting a light bulb in the battery line is a good method when tracing shorts. Shows the short without blowing the fusible link.
 
@KitCarlson , your inbox is full. I seem to remember the pulsing voltage output on those also. You can see it on a fuel gauge when filling up and also the lack of one on a an old Euro sports car (Fiat 850) whose gas gauges seem to swing when going over bumps! I wonder if they did that to mellow out the fluctuation readings over time.
 
Garys72Duster said:
OK, I found it. The wiper switch/motor is the problem. Disconnected that, and now no more excessive current draw. I noticed it when the amp meter was hooked up, and I turned the ign sw on, it would jump all the way to the left-discharge. So I took the wires off the amp meter, and when I touched them together with the key on, it sparked alot. Also put a test bulb in series there, and it got really bright. So the wiper switch and motor is shorted to ground. Re hooked the wires to the ammeter, and it barely moves to the left now, when you turn the ign sw on. Had I left the key on, with the wiper motor hooked up, I'm sure we would be seeing some wires smoking! That's what I like about the ammeter, it gives you an immediate readout of which way the current is going, and how much. Whew, Dodged a bullet there!
Click to expand...

You are learning!!!!
 
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