Voltage limiter problem?

[Manfred318]

My old limiter finally crapped out on me, so I went and bought a new one from the local Dodge dealer. I put it in the car and nothing happens. I checked it with a 10 amp resistor, and the gauges would shoot up about 3/4 of the way and drop off down to around 1/4 of the way up. Is it most likely a DOA limiter or could it be another problem?

[Ghoste]

The panel is well grounded right?
That said, replacement limiters are also somewhat notorious for being junk even when replaced.

[Manfred318]

Its grounded Ive even added an extra ground just to be shure.

[Ghoste]

Did you run a test on the limiter itself?

[Manfred318]

I checked it with a resistor.

[Plumcrazy]

Assuming the cluster is properly grounded and all three gauges have the same problem, that would sure look like a bad voltage limiter.

They can be tested to see if they work at all.  http://1970chargerregistry.com/70messageboard/viewtopic.php?t=2055

Unfortunately that test won't tell you if the limiter is calibrated to supply an average of 5 volts.

I'd try another voltage limiter.

[Manfred318]

If it doesnt supply the 5v can it be adjusted? I noticed it has a little screw on the bottom, and was wondering if that was for adjusting the voltage.

[Manfred318]

I just checked it and I do get a very slow pulsing on the test light. 

[trev-68]

hi manfred i had lot of problems with my mechanical regulator, tried to adjust it but it was still crap, then i got a solid state elecronic one from fbo systems, and it cured my charging problem instantly, the cost of the unit was not much either, hope this is of some help.

[Plumcrazy]

If it doesnt supply the 5v can it be adjusted? I noticed it has a little screw on the bottom, and was wondering if that was for adjusting the voltage.

I think it is but I've never tried doing it.

What was the problem with the original voltage limiter?

[Manfred318]

If it doesnt supply the 5v can it be adjusted? I noticed it has a little screw on the bottom, and was wondering if that was for adjusting the voltage.

I think it is but I've never tried doing it.

What was the problem with the original voltage limiter?

It quit working. I wasnt getting the pulsing voltage to the sending units, the test light would stay on constantly when I checked it.

[Plumcrazy]

If it doesn't supply the 5v can it be adjusted? I noticed it has a little screw on the bottom, and was wondering if that was for adjusting the voltage.

I think it is but I've never tried doing it.

What was the problem with the original voltage limiter?

It quit working. I wasn't getting the pulsing voltage to the sending units, the test light would stay on constantly when I checked it.

I'd still try another regulator, but when a voltage limiter fails in the way yours did it can damage the gauges.

[Manfred318]

If it doesn't supply the 5v can it be adjusted? I noticed it has a little screw on the bottom, and was wondering if that was for adjusting the voltage.

I think it is but I've never tried doing it.

What was the problem with the original voltage limiter?

It quit working. I wasn't getting the pulsing voltage to the sending units, the test light would stay on constantly when I checked it.

I'd still try another regulator, but when a voltage limiter fails in the way yours did it can damage the gauges.

What would be the best way to check for damage? I found an old regulator I had on a spare cluster and put it in earlier, and the guages will work but they do not read like they should. The temp guage for example once the car warms up it will only read up to around 120*. Shut off the car and crank it up again it will go up to 170*-180* and drop back down to around 120*. The oil pressure does the same thing as well. The regulator I found seems to test out fine with the test light, I get a nice constant pulsing.

[Ghoste]

To be honest, I think they were notoriously inaccurate right from day one.

[Plumcrazy]

I would use the voltage limiter you found because it sounds like it's working properly.  Then just put your 10 ohm resistor between the sending unit leads and ground, that should move the gauge to full scale.

Those gauges have a heating element wire wound around a piece of bi metal that will bend when it gets hot.  When a voltage limiter fails and applies a constant 12v to the gauges it can permanently distort that metal.   I'm not sure if somebody repairs something like that or not.

[Manfred318]

I would use the voltage limiter you found because it sounds like it's working properly.  Then just put your 10 ohm resistor between the sending unit leads and ground, that should move the gauge to full scale.

Those gauges have a heating element wire wound around a piece of bi metal that will bend when it gets hot.  When a voltage limiter fails and applies a constant 12v to the gauges it can permanently distort that metal.   I'm not sure if somebody repairs something like that or not.

Yea I'll just use the one I found. At least the gauges work somewhat and thats better than nothing at all. I will check it out with the resistor this afternoon and see what happens.

[Manfred318]

Ok checked this afternoon with the 10 ohm resistor and  the temp gauge immediately went up to just under 230* then very slowly made its way up to 230* and stopped. The oil pressure did the same going up to around 50 lbs and very slowly making it up to 60 lbs and stopping.I didnt check the fuel gauge, but I assume it will do the same. I did manage to do some adjusting the new regulator with that little screw. I ran the screw all the way up and I got a slow dim pulse, but if i run it all of the way down I get a nice bright constant pulsing. I will put it in tomorow and see what happens.

[Paul G]

I made my own voltage limiter using these directions. http://www.imperialclub.com/Articles/GaugeRepair/ It holds a rock solid 5 volts and the gauges work flawlessly every time. I feel pretty confident they are correct now. It was actually pretty easy to make and only cost like $5 for all the parts from Radio Shack.

[Manfred318]

Hey thanks alot I'll give that a try. Ive got them working pretty good now by running that little screw all the way down, it seems to be holding a constant 5v but if I can do away with that thing I'll give it a shot!!

[Plumcrazy]

Hey thanks alot I'll give that a try. Ive got them working pretty good now by running that little screw all the way down, it seems to be holding a constant 5v but if I can do away with that thing I'll give it a shot!!

I built an electronic unit for mine this last spring.  It's worked flawlessly so far. 

[Manfred318]

OK so I finally got around to doing the electronic conversion and doing away with the old limiter, but alas I have a problem. I followed the instructions exactly as they were on the paper and now it seems my gauges are worse than they were when I had the old regulator in there. One problem is the gauges are slow and I do mean s l o w to work. Another thing is they do not seem to be giving accurate readings. Before I did the swap I would carry around 25-30lbs of oil pressure now it shows barely 10. The fuel (I have over 1/2 tank and now only showing 1/4 at the most) and the temp (180* before and now barely registers) does the exact same thing. Did I possibly do something wrong when I made the electronic regulator? Any help would be greatly appreciated

[Manfred318]

Update...
I just went out and grounded out the guages the Temp guage maxed out at 230* and the oil pressue maxed out at 60lbs I didnt check the fuel but I assume it will be the same results.. So I assume the problem is with the new regulator I rigged up? 

[Paul G]

Pull the wire off of the temperature sending unit and measure the voltage at the wire to ground. It should read 4.9 volts or better. If it does your IVR is working, if it does not recheck your work on the regulator. Make sure you have a good engine ground. Ground strap from the engine to firewall and the smalller wire from the neg cable at the battery to the body must be in good condition and securely fastened..

[Manfred318]

Everything seems to check out fine. I have cleaned all of the ground locations and tightened them down, but still I have the same problem. Ive checked and rechecked the regulator and it looks right according to the picture. Could I have possibly used a wrong limiter or capacitor? I bought a 7805 5VDC regulator rated at 1 amp and a 46uF 35w capacitor. Any ideas?

[Plumcrazy]

Everything seems to check out fine. I have cleaned all of the ground locations and tightened them down, but still I have the same problem. Ive checked and rechecked the regulator and it looks right according to the picture. Could I have possibly used a wrong limiter or capacitor? I bought a 7805 5VDC regulator rated at 1 amp and a 46uF 35w capacitor. Any ideas?

Just get a digital voltmeter and check the output voltage of the regulator you built.  It should be 5 volts plus or minus about one tenth of a volt.   Unfortunately my guess is that the previous regulators damaged your gauges.