Still No Working Temp Guage, Out Of Ideas

[LRoak]

Hi, this is my first time posting. I've looked for the next step on the forums but I am out of ideas.

My engine temp guage just pegs to high whenever I hook it up. It worked last year before I tore into the restoration. It's a 65 coupe. Here is what I have done:

I first replaced the sending unit. Tried a few wires and got it working. Go forward a year and now it just pegs at high. I thought maybe there was a short in the wire and it was grounding somewhere along the way. I ran a new wire on the outside of the car and hooked it up. Same result. I thought maybe the voltage limiter was bad, because this is not my only cluster issue, so I replaced the limiter. Same result.

I then pulled a guage out of another 64 coupe to see if it was the guage itself. I got the same result with the other guage.
One thing to note, I thought I was supposed to be getting pulse current out of this limiter but it is just constant, is that the problem?
What can I try next? Any help would be appreciated. Thanks guys.

 

[tos]

What changes have you made over this year? Are you talking about the small voltage regulator on the back of your instrument panel? This is an IVR or instrument voltage regulator. You mentioned you are having other cluster issues, What other issues are you having?
I would first make sure you have the correct wiring diagram (diff years look the same but have diff color coding) and verify your wiring. Second I would check the voltage going in that limiter and coming out (you should get about 5v or slightly more coming out to the gauges). Does your fuel gauge read properly? I would do a continuity check on the ground wires coming off your panel to insure your getting a good ground.

also when you measure voltage out of your limiter (IVR) you will see it as constant voltage although it is actually Pulsed or alternating current but too fast for you to see on a multimeter

One other thing to check for sure is that your engine is grounded to the frame properly (this is very important)

 

[LRoak]

Yes, when I replaced the IVR I bought a new one. The ground to the engine is tight and I have the correct wiring diagram. At least the wires I have come across match up in color to the diagram. There are wires here that are not on the diagram and that I have traced and they dont appear to go to anything. Some hack jobs were done before I owned the car for sure.
Some of the other cluster problems I am having are
The fuel gauge (although I think I got this one fixed, it was a broken wire, at least it reads full now and I know the tank is full)
The oil light used to stay on the whole time but I think I got this figured out as well, I believe I had two wire that were crossed that were bundled together with the temp sender unit wire.
The high beam indicator light and the blinker indicator light both stay on the whole time as well.

Also, I understand that if I checked the pulse current with the volt meter that I might not see it pulse, but I checked it with a light up circuit tester and it was still solid. Would I be able to see it pulse then? I thought so because of another youtube video that I watched showed one pulsing.

 

[tos]

Are your headlights and blinkers operating properely? If so then I would start at the instrument panel and work back. They may all be related. Sounds almost like your feeding voltage in from somewhere due to a miswiring?
Can you post a pic of the back of your instrument panel?

As far as your testlight you may detect a slight flickering but that IVR as with any voltage regulator is there to regulate and smooth out voltage. Im not 100 percent positive on the testlight reaction cause ive never had a need to do that test but it may also depend on the quality of your light and how quickly it can turn on and off between pulses.
You may be able to pick up differences when the main voltage regulator kicks in and out?

 

[LRoak]

Yes, I can post a picture of the back of the panel. Am I looking for something in particular? I noticed in a few others' pictures that there was another wire coming off the IVR, which I assumed was a ground. I hooked up a wire and grounded that too, but it didnt seem to change anything.

 

[tos]

Nothing inparticular just helps me visualize and another set of eyes cant hurt.
Snap a shot of the inside of your dash if you can get a good one.

Is this an early 65? (64 1/2) that originally had a generator?

 

[tos]

You should have two blade connectors to your ivr, one with an extra wire. they should all be black/green and the extra one should go to the water temp gauge.

Just noticed on one of my diagramns that the IVR is also refered to as the constant voltage unit so this should eliminate testing for "pulsed voltage"

 

[LRoak]

Well here they are.
No the car is a 65 and never had a generator as far as I can tell.
As you can see there are some wires that just go to nothing. Example, the long green one on the left side, it changes colors a few time and both ends are cut and loose. There are also a few of the bullet type female connectors with no male ends.
Oh and the green ground wire on the back of the cluster is the one that I added and grounded to the shifter temporarily just to see if it would change anything.

 

[tos]

Ok I assumed you had everything plugged into your panel still.
The ground wire you added I don't think will affect the ivr/cvu because I think the shell of it isn't connected or grounded inside the unit, it is just a shell to hold the unit.
Is that a new blinker switch assembly?
One of your wires going to your gauge pod should be grounded under your dash on the right support framework along with some wiring off the wiper motor, so I would make sure that is grounded there properely.
Grounding to your shifter wont always give you a good ground due to the use of plastic and rubber bushings in the shifter mechanism.
Since everything is unplugged you'll have to do a process of elimination(which you may have already done).
- I would first turn the key on and start with the ivr wires and test for voltage (including the ground wire), also test the plug of the ground wire to the frame (continuity test) (im assuming you have a digital multimeter)
- If that all checks out then plug in the IVR and test the ground side and see what your output voltage is (somewhere around 5v)
- Back to the blinker switch, if new I would unplug it and verify proper wiring - I had one that was pinned wrong and also my new harness to my dimmer switch was wired wrong causing all kinds of headaches.
-- Do your blinkers work ok? can you hear the relay? they can stick.
- Go one circuit at a time and if it works plug it in and go to the next

 

[LRoak]

Sweet, Good info. Ill give it a try and let you know.
Yes that is a new turn switch. I could hear the blinkers before I installed it, but I would have to listen again to be sure that I can still hear them.
The shifter should be ok, its a hurst and its pretty solid. I will try another ground though.
One other thing, there is no ground wire to the IVR... is that the problem? do you have a picture of what that ground looks like or where it goes?

 

[tos]

This is not the best wiring diagram but shows the ground and im pointing out in your pic where that is

 

[tos]

here is a clearer pic BUT this is of a 66 panel and has more detail, however the ground setup may be different but yes it needs to ground one way or another either thru a gauge or its own individual ground in order to complete the circuit. Poor or no ground causes more issues than anything else. I'm not sure if yours grounds directly to the frame like the 66 year diagram but ill try to find another diagram that has more detail.

 

[LRoak]

Ok. I found the ground. I hooked the ground to the voltage limiter and hooked everything back up. Turned the key and nothing happened with the gauges. Then smoke started pouring out of the dash. One of the wire off the voltage limiter was heating up, burned the jacket rift off the wire.

 

[tos]

Not good. Im not sure if it makes a difference but it looks like your wires on your limiter are reversed.
Did you test the voltage in and out like I suggested? Did you only get 5v (less that 6v)?
Did this blow any fuses?
First pull only that cooked wire off and turn your key back on and check for voltage to that wire.
Then do an ohms test between the prong that the wire was plugged to on the limiter and to your ground point under your dash (what do you get?)

 

[LRoak]

The wires cannot be reversed. One is female and the other is male. I can't get any reads on voltage in. The only read that I can get is on the burnt wire and it's right at 12 volts. Ohms test on that wire reads .2-.3. As for the fuses it may have blown one if there was one to be blown... Many have blown, kinda hard to tell now what's blowing what. One of those new wiring harnesses is looking nice right about now.

 

[tos]

It may be that your limiter is shorted out internally. Did you check continuity between the terminals and the limiter housing? Disconnect both the wires and check one blade on the limiter to the limiter housing. Then do the other blade. what are your readings?

 

[tos]

The wires cannot be reversed. One is female and the other is male. I can't get any reads on voltage in. The only read that I can get is on the burnt wire and it's right at 12 volts. Ohms test on that wire reads .2-.3. As for the fuses it may have blown one if there was one to be blown... Many have blown, kinda hard to tell now what's blowing what. One of those new wiring harnesses is looking nice right about now.

That is true, I just saw in your pic that the secondary wire looked like it was wrong but after blowing up the pic I could see it better, My bad.

Lets go back a little. Because the diagram I posted doesn't really show that well and I shouldn't have posted the 66 cause it may confuse.
1 - Does your wire that smoked turn on and off with the ignition?
2 - Where does the other wire go (terminal with two wires)? The short one should go to one gauge (water temp I think) and the long on should go to the other gauge (fuel)

 

[LRoak]

The other wire goes to the other peg on the temp gauge. The fuel wire are on the other side of the harness.

I bought another ivr from npd that was supposed to give me 5 volts out no matter what goes in. I am getting a solid 8.1 out. Would that be enough to make the gauges peg high?

And yes, the wire that got hot does turn off with the ignition. It is not getting hot anymore since I took the ground wire that I had from the old ivr to the frame off.

 

[tos]

Yes that extra voltage can cause those gauges to read wrong. To read properly they need a calibrated voltage passing thru them. it doesn't have to be dead nuts exact but I would say within a half volt of that 5v. If you don't have the proper volts into the gauge then you wont have the proper volts out and that's how those gauges operate (off of measured voltage. The sending units for those gauges are basically rheostats which change voltage as they move. If you look on the side of your fuel sending unit you will see a winding of thin wire that is heavy on one end and less winding on the other (you'll have to remove a cover to see this). As that arm moves up and down it allows more or less voltage to travel thru. Temp sender is the same principle but works off of heat to operate it but is basically a rheostat.
Check that ivr to see if it is adjustable. I ended up making my own that is adjustable so I could tweek it my self.

 

[LRoak]

I talked to a guy at National Parts Depot and he said he would have to contact the manufacturer to see what is going on. It says right on the add that it will put out 5 volts and that they is no adjustment needed. It doesnt have a set screw like the other one and I dont see any other way to adjust it.