Has anyone ever adjusted this little screw on the solid state IVR?

[toddz69]

I'm curious if anyone has ever adjusted this screw on R4 on the solid state instrument voltage regulator for the dash cluster? WH's description seems to indicate no adjustment is needed and Tom's description states it can be used for adjustment.

I replaced my original mechanical one last fall when it started to fail and then a few months ago my fuel gauge started not reading as accurately as it did previously and I was wondering if maybe the IVR could be adjusted a bit to compensate.

Thanks,
Todd Z.

 

[DirtDonk]

Yes, I've done it. But the ones I messed with did not look exactly like the one in the pic. We must've changed vendors, or just as likely, the vendor changed vendors, and the manufacturer changed designs, in the past few years.
In fact, I sat there in my office at WH and tweaked every one of the units we had in stock at the time, because they were all slightly off!
That little "office party" was the result of a phone call from a customer that said theirs was showing a low output, and his gauges were reading low. A simple twist of the screw raised them from the 3v that they were indicating (they were not all the same though), to the 5v that my memory said they should be.
Probably 6v would work as well, and perhaps be even more appropriate. But at the time I did not have any exact specs for the originals. Just my memory of using an analog meter on my original '71 IVR.
Which I also adjusted by the way.

Which way is your fuel gauge reading? And, if it's the IVR, which way are your other two gauges reading? Harder to correlate perhaps, but if it's far enough off of the baseline, that should be visible in your Oil Pressure and Engine Temp gauges as well.
Have you measured the output of your IVR to verify it's the culprit? Could be the new-fangled fuel sender too I suppose.
Didn't you change yours over to one of our tanks with the new style sending unit?

Paul

 

[Broncobowsher]

Todd, do you have any other factory gauges still hooked up to the IVR? Have they drifted like the fuel gauge has? If ALL the gauges have drifted the same direction, that indicates an IVR issue. If it is just a single gauge, it is NOT and IVR issue.

I have tuned the IVR in the past, just the mechanical one. Never tried the electronic one. Personally I feel the mechanical version has better engineering being temperature compensating and first start warm up boost all automatic. The mechanical wear issue just sucks.

 

[toddz69]

Todd, do you have any other factory gauges still hooked up to the IVR? Have they drifted like the fuel gauge has? If ALL the gauges have drifted the same direction, that indicates an IVR issue. If it is just a single gauge, it is NOT and IVR issue.

I have tuned the IVR in the past, just the mechanical one. Never tried the electronic one. Personally I feel the mechanical version has better engineering being temperature compensating and first start warm up boost all automatic. The mechanical wear issue just sucks.

The only two I have connected are the fuel gauge and the temp gauge (4G so no ammeter and I run a mechanical oil pressure gauge so no oil pressure gauge).

I've been noodling this around in my head in terms of "have they both drifted" too - I generally feel so. I think my temp gauge is a little low too *but* it's always been low compared to the mechanical gauge which I trust a lot more. Seems like my temp gauge is probably running between 170-190 these days with the mechanical reading 200-205 while in the past I would say at this time of year it (the electrical one) would be around 190 most of the time.

Todd Z.

 

[toddz69]

Yes, I've done it. But the ones I messed with did not look exactly like the one in the pic. We must've changed vendors, or just as likely, the vendor changed vendors, and the manufacturer changed designs, in the past few years.
In fact, I sat there in my office at WH and tweaked every one of the units we had in stock at the time, because they were all slightly off!
That little "office party" was the result of a phone call from a customer that said theirs was showing a low output, and his gauges were reading low. A simple twist of the screw raised them from the 3v that they were indicating (they were not all the same though), to the 5v that my memory said they should be.
Probably 6v would work as well, and perhaps be even more appropriate. But at the time I did not have any exact specs for the originals. Just my memory of using an analog meter on my original '71 IVR.
Which I also adjusted by the way.

Which way is your fuel gauge reading? And, if it's the IVR, which way are your other two gauges reading? Harder to correlate perhaps, but if it's far enough off of the baseline, that should be visible in your Oil Pressure and Engine Temp gauges as well.
Have you measured the output of your IVR to verify it's the culprit? Could be the new-fangled fuel sender too I suppose.
Didn't you change yours over to one of our tanks with the new style sending unit?

Paul

Thanks for the input and your experiences, Paul.

Yes, I have one of your new sending units in my M1A1 that I installed in the fall of 2020. Prior to that I used various other 23 gallon tanks with the old style swing arm senders that always read 3/4 when full and then got to E with 7-8 gallons left in the tank. Always annoying but I learned to live with it. When I installed the new sender, I would get between 3/4-F on the gauge and when the gauge got to E, I would have about 3 gallons left - perfect. Bliss for a little over 5 years until one day I was out 'wheeling a few months ago and filled up the tank in the morning - gauge read correctly. I filled up on the way home and it only went to 3/4 full on the gauge again....wtf? So now with my checking, I'm back to the old swing arm sender readings of 3/4 on the gauge when full and about 7-8 gallons when I get to E. Very annoying!!

See my response to Tim above about the gauge readings. I did do some checking with the sending unit - grounded the feed wire with the key on and got the gauge to go up to F (actually a little past) and verified I had a good ground on the other lead so I *think* the gauge is working properly. I haven't pulled the sending unit to check resistance measurements yet to make sure they're in the 10-73 ohm range. I did stick my DVM on the IVR and as you know, it's a pulsed output so hard to verify it but I'd say the most common output reading appeared to be in the 4.5-5V range.

I've noted that your sending unit you offer for the M1A1 tank on the website is a little different (potted top with factory connector) than what comes with the tank kit (or what used to come with the tank kit). Did you switch sending unit suppliers?

TIA,

Todd Z.

 

[DirtDonk]

You mean, your current one is pulsing, or your original?
If an IVR is pulsing, then it is not an electronic version. Unless they have created one that mimics the functionality of the original.
Otherwise, as far as I know, all the modern electronic versions show a rocksteady output that is easily tracked with a digital voltmeter.

 

[toddz69]

My current, electronic one, purchased from WH, is pulsing.

You can see it doing that in this video from one of your competitors by Mr. Melton:

About 4:45 in the video.

All other indications online are that they pulse as well. If they don't......then I stand corrected!

Thanks,
Todd Z.

 

[DirtDonk]

Very interesting. It’s all new to me then. Every electronic one I’ve ever tested was steady as a rock.
One voltage. When I was adjusting the incorrectly set ones, I could see the volts rising ever so slightly as I turned the rheostat.

 

[toddz69]

I may try that myself just to give it a shot...

Thanks!

Todd Z.

 

[serial car restorer]

I have that same IVR, but haven't tested its output yet. But I suspect its output is a little low, as all 3 gauges read lower than I expect they should.

 

[ksagis]

Do both the electronic and old school IVRs pulse? If new ones pulse, a possible answer is that when @DirtDonk tested previously it might have been with a analog “needle” multimeter. Those wouldn’t respond fast enough and would show the average.

Or maybe he had a slow responding DVM

 

[toddz69]

Well, I went down the rabbit hole a lot further online last night and found a lot more evidence that the new solid state units do NOT pulse - their output is constant as @DirtDonk noted above.

So, when I have a moment, I think I'll take it off and test it on the bench and see what I get for results.

I'm sure you can all relate - all my dreams/thoughts last night were about grounding/testing IVRs .

Todd Z.

 

[Oldtimer]

My dream would be . . . I hope Todd documents the ground/test procedure, so I don't have to think about it.

 

[toddz69]

My dream would be . . . I hope Todd documents the ground/test procedure, so I don't have to think about it.

LOL - I think I sampled enough youtube videos last night to do it right!

Todd Z.

 

[73azbronco]

My understanding is if you adjust the screw, a Prius bursts into flame.

 

[ksagis]

Quick, lets all adjust them at the same time

 

[DirtDonk]

I think that’s only if you cut the blue wire.

 

[toddz69]

So I had some time tonight to futz with this so I headed out to the garage, contorted myself, and sweated a lot.. a balmy 110-ish day here in Phoenix today. Initial reading on the IVR output was 4.86V. Dug out the tiniest Phillips screwdriver I have, put on my magnifiers and turned the screw as much as I could. Peak value I got was 5.79V, and since these are 6V gauges, I decided to try this and see what I got. 4.86V was the lowest reading, btw.

Oh, and the R4 solder joints had some flux on them so that was cleaned off prior to reinstallation. Checking quickly with the key on brought the fuel gauge up to between 3/4-F again - a good sign. Based on my odometer, I'm guessing that I've burned about 4 gallons since I filled it up. The M1A1 usually shows full for a long time since the sending unit is recessed in the tank top.

I'll try and do some more driving in a few weeks to see how well the gauges are working now with the increased voltage.

Todd Z.

 

[serial car restorer]

Thanks for the update, Todd. I'll see if I can contort myself under there and try this sometime soon, maybe this weekend.

 

[toddz69]

So I had some time tonight to futz with this so I headed out to the garage, contorted myself, and sweated a lot.. a balmy 110-ish day here in Phoenix today. Initial reading on the IVR output was 4.86V. Dug out the tiniest Phillips screwdriver I have, put on my magnifiers and turned the screw as much as I could. Peak value I got was 5.79V, and since these are 6V gauges, I decided to try this and see what I got. 4.86V was the lowest reading, btw.

Oh, and the R4 solder joints had some flux on them so that was cleaned off prior to reinstallation. Checking quickly with the key on brought the fuel gauge up to between 3/4-F again - a good sign. Based on my odometer, I'm guessing that I've burned about 4 gallons since I filled it up. The M1A1 usually shows full for a long time since the sending unit is recessed in the tank top.

I'll try and do some more driving in a few weeks to see how well the gauges are working now with the increased voltage.

Todd Z.

An update on this challenge. After I adjusted the IVR and got back from vacation, I took the truck on a 350 mile day trip. I immediately realized the voltage was too high as my temp gauge was reading 210-215 all the time and my engine was nowhere near that hot.

I worked on adjusting the extremely tiny screw on the IVR again and didn't do my best work and stripped the head on the screw.

Soo.........I found a source for NOS IVRs online for a pretty cheap price and ordered one. I finally got it installed yesterday (I'm getting pretty good at R&R'ing these things by now) and took it for a ~3 mile drive to the store today. A balmy 108-110 here today so I knew it would come up to temp pretty quickly.

Wouldn't you know it - the NOS IVR seems to be perfect! Gas gauge is reading pretty well (more testing on that to confirm as it empties, of course) and the temp gauge is more accurate than it's been in years. As a good friend noted recently (his truck is one year newer than mine) - "Todd, my original IVR is still working fine 56 years on.....". And mine made it 56 years too (died last fall). Unless something changes with this NOS piece, I think I'll run it and let the grandkids worry about it in 50 years after I'm long dead and gone...

Todd Z.