Yes! I've been the point person on a couple of things, so maybe I can follow?

 

But, I did just order three sets of 10, 22, and 75 (73's weren't available) ohm wire-wound resistors to use as calibration resistors. These represent the full scale, mid-range, and bottom of the range resistances the senders give. My thinking is to use these in conjunction with a variable-voltage power supply to find the voltage that will give the correct readings at full scale and then check to see that the other readings are correct as well.

However, I won't get them for a few days so you still have time.

 

Got the resistors in today that I'll use to test the gauges. So, I decided it was time to start on the variable regulator. I found a 575 ohm potentiometer and a 160 ohm resistor and wired up a postage-stamp sized regulator, as shown below. That resistor combo allows the voltage to be taken up to about 5.6 volts, and it is easily adjusted in small voltage increments. So, I hope 5.6 volts is enough to take the gauges to full scale, and I hope to find out tomorrow.

The last picture shows the voltage and current being supplied to the light bulb. Obviously 50 milliamps isn't nearly what the gauges will pull, which will probably be something like 750 milliamps depending on the voltage that is needed. But, I'll need to get a heat sink for the regulator to allow it to handle that much current, and that's a minor problem since the tab will be at the output voltage of the regulator. So, it will also have to be protected.

 

Alright, Gary. When I first met you at your shop, I thought you were/are a master machinist. Now, I have no idea if you were a master machinist or an electrical engineer because let's face it, most people don't build circuits from scratch or R&R ICs in factory made modules (such as the Edelbrock unit for your O2 monitor), let alone own an oscilloscope. LOL!

As always, interesting reading on this forum. Thank you and keep it up!<O</O

 

Yaga - You must not know any machinists or you wouldn't be so easily led astray. But, I'll take that as a compliment and I thank you!

As for the o'scope, IC's, et al I was an amateur radio operator at the age of 12. I remember Dad having to take me to the meetings, and later he told me that he considered it time and money well spent as I was both learning and not getting into trouble. And, for my equipment I built Heathkit and Allied Radio receiver and transmitter kits. In fact, I've probably built more kits than I've built engines, and I've built several of them.

After graduation with degrees in math and physics I worked for a power company and became responsible for their computer systems that controlled the generating plants and the substations. There I learned to troubleshoot computers with an o'scope down to the chip and, since the repairman was frequently a long way from Wichita, to repair them as well. So, I understand the basics of electronics and how to fix things.

 

I ran the test with the regulator today and it works perfectly. Here are the conditions and observations, and then a bunch of pictures. Basically I ran these tests:

• Rusty's cluster and ICVR
• Dad's cluster and ICVR
• Rusty's cluster with the regulated power supply instead of the ICVR
• Dad's cluster with the regulated supply instead of the ICVR

Each of the above were run with the following resistors on the inputs representing the senders:

• 10 ohm, which the shop manual says should take the pointer to full scale
• 22 ohm resistor, which the manual says should make the gauges read "mid-scale"
• 75 ohm resistor, which the manual says should put the pointer on the bottom of the scale.

In other words, I ran 12 tests: 4 different combinations of cluster and voltage regulator, and 3 different sets of resistors. And, I took pictures of each test, and stored them in my ICVR Testing album. I apologize for the seemingly haphazard order of the pictures in the album. I selected them in the order they were taken, which was exactly as outlined above, but I forgot that FTE displays them in FILO order - First In/Last Out.

You can go peruse the pic's to your heart's content, but let me show a few of them here and draw some conclusions. Here's Rusty's cluster with the Ford ICVR and 10 ohm resistors. Note that the oil pressure gauge isn't reading full scale. But, if you blow the picture up you'll see it is literally pegged. So, we need to use the fuel and temp gauges for these tests, and the fuel is reading exactly on Full and temp is slightly above the scale. These are the readings we want to replicate with the regulator.


Here's the same cluster and resistors, but with my voltage regulator in place with its output set to basically 5 volts. Note that the readings are low, and I suspect this is what Stangrcr1 is seeing since he used a 5.0 volt regulator.


And, here's what the gauges show when they get basically 5.4 volts. I think that is pretty much the magic voltage.

Here's the same cluster with the ICVR and the 22 ohm resistors simulating mid-scale:

Here's the same thing with the voltage regulator in place of the ICVR:

This is the same cluster with the ICVR and 75 ohm resistors simulating the bottom of scale readings:

And here's what the 75 ohm resistors give for the bottom of the scale when using the regulator:

So, it looks like 5.4 volts will replicate the readings given when running a good ICVR. From the time I cranked the voltage up to that setting I didn't touch it for the rest of the tests, and all the tests with my regulator at roughly that voltage got the same results the ICVR gave - both on Rusty's cluster and Dad's cluster, and with all combinations of resistors.

Further, it looks like the LM317T will do the job as the regulator even with the resistor in the harness. I simulated it by making up a resistor pack of a 10 ohm 2 watt resistor paralleled by two 100 ohm 1/4 watt resistors, which brought the total resistance down to 8.5 ohms. And, to ensure that pack didn't get into any of the other wiring I slipped a piece of shrink tubing over it without heating it. However, the first test using the ICVR and 10 ohm resistors pulled enough current to shrink that tubing right down around the resistors. Later, when using the voltage regulator I saw the output voltage sag a bit and found that the input voltage to the regulator had gone below the set point + 2 volts. But, the battery voltage was about 13.25 voltage, so when the engine is running I don't think there will be a problem. And in any event the gauge readings hadn't changed.

So, the next step is to fix the regulator's voltage to 5.4 and figure out how to package it so I can put it in the truck. I'm planning to take it up to see Dad on Friday, so that should be a good test of the regulator as well as the carb jetting.

 

Two things to report today. First, Yaga asked me a very good question, which I paraphrase here: Why are you doing this? Is the goal simply academic, just to know how the gauges and ICVR work, or are you planning to replace your ICVR?

I'd actually been thinking about that myself, and had come to an easy answer. But, Yaga suggested I put that answer as an intro to this thread, so I have. Here's what it says:So, the rest of this thread is intended to document my efforts to make the factory gauges work properly. And, that leads me to the second thing to report today - I took an ICVR apart, took three pictures of it, and posted them in my ICVR album. Here are two of them:





The input terminal is the connection that goes through the plastic in the right-center of the first picture, and in the upper-center of the second picture. From there the connection is to the contact that is jacked up by the adjusting screw in the center of the second picture. When that point is touching the second, movable, contact the current flows around the U to the output terminal and on to the gauges. But, it also flows through the heating wire that is wrapped around the U, and since the U is made of two different metals that expand at different rates the contact eventually comes off the stationary terminal, the current both to the gauges and to the heating element stops, and eventually the U bends back such that the contacts touch again and the process starts all over. And, by the way, that proves that the circuit in the 1981 Truck Wiring Diagrams is wrong because it shows the heating element connected to the input terminal, not the output terminal - as shown below.

Anyway, now I'm trying to figure out how to use the case of the ICVR as a heat sink for the voltage regulator IC. Unfortunately the case is ground but the tab of an LM317T is the same as the output terminal, so I can't just mount the IC to the case. I'm thinking about one of the thermal pads that insulate electrically and mount the regulator to the case using a nylon screw. Or, maybe a regulator which has an electrically-neutral tab. Got a better idea? I'm certainly open to any and all ideas.

 

Gary... I really wish you would reduce the size of your pictures, don'tchya think over 2,000 pixels wide is overkill? I can appreciate the detail they show, but, why so big?

Might use a photo-editing program to crop 'em? Or, select (copy) an area from a picture, and paste it into a new picture.

 

For me I am interested because this replacement IVR can be made for 2 or 3 $ in parts. Autozone and the like wants over $50 for the part and who knows what the dealer cost is?

 

Great work Gary. You are a lot like me, people who really don't know me well think I am a pretty good mechanic. They don't realise I was raised by a guy with a Masters in EE (from MIT) and learned at an early age how to read a tube characteristic chart and figure plate voltage grid voltage and bias. I too built a lot of kits as a kid and still do some electronic work on occasion.

I also, like you, never shrink from a challenge. On your ICVR heat sink, Radio Shack used to sell a finned aluminum heat sink. I don't see why you couldn't remote mount it insulated and just run leads to the cluster. FWIW, this is probably applicable to all 12V Ford gauges through 1988.

 

I'm just using the pictures my 10 year old digital camera takes. I'll check to see if I can tell it to take smaller pictures, which I think it will do, but I'd rather not have to take the time to crop them. Is it all the pictures, just the ones I attach, those I put in my albums, or?

And, the ones for $50 are nothing more than what we already have. I see no reason that our gauges can't be accurate if we feed them a fixed voltage.

You'd probably know how to use my grid dip meter then, wouldn't you. And, you'd understand the term "5 tube super het". I'll never forget when I was in college walking up to a friend that was cramming for a test in electronics - which I wasn't taking. Looked over his shoulder and said "5 tube super het" and he freaked out. How could I know that? Then it got even worse when I started naming the tubes: 35W4 for the rectifier; 50C5 for the amp;..... But, I had to know that for my amateur license. It is basic stuff, all radios were made that way.

Unfortunately, Radio Shack has made most of their stuff "web only". But, I buy from Digikey and their service is spectacular. I ordered those resistors for testing the gauges at about 7 PM CDT Friday night. Got an email a few minutes later that they'd been shipped USPS, and they were in my mailbox on Monday afternoon. They have a small box that I could use if my idea of mounting the thing doesn't work out. But, your idea of remote mounting the thing is something I hadn't thought of, and I really like it. Thanks!

 

Anything in an album has a max size of 1024 x 768, the software automagically shrinks 'em if necessary.

Attachments, though, aren't limited like that.

Click around on your camera, it has to have the ability to make smaller pictures (although having the camera remember that setting, dunno about that).

Those of us with smaller screens and/or slower connections thank you.

 

I found a setting of XGA on the camera, which is said to be 1024 x 768. I'll give that a try. But, I don't know if it'll stay there when I change the batteries, which happens quite frequently as the old cameras were power hogs. So, you may have to remind me.

 

Why don't you just get one of those apps that will resize all pictures in a specified location to a specified size? Won't have to worry about the camera or anything.

 

Because that is another set of steps. I pull the memory card from the camera, plug it into the computer, and select the shot I want via Manage Attachments or Upload Pictures.