ELEC--temp and fuel gauge out!! Help

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stillandystill

stillandystill

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1972 valiant 225.
Temperature gauge and fuel gauge out at same time. First I noticed the temp gauge fly all the way maxed out. Car not overheating. Then later that day the fuel gauge was bouncing between full and empty. Now they both sit all the way to the left. I was able to bypass the temp sending unit, attached wire from positive battery to the wire that connects to sender. No jump in needle. Checked for continuity to fire wall. Good. That's about as far as I got.
Looking at the wiring diagram for the back of the instrument cluster, I notice a voltage regulator that potentially changes the 12v to 5v? Could this be the problem? Also, how do I test all these gauges with a multimeter? Can I test for resistance or continuity? Or just volts ?
I want to get a jist of it before I take down the steering column and remove the panel. Thanks
Andy
 

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Yes, it's almost certainly the instrument voltage regulator (IVR). You can buy a replacement -- RockAuto has them -- or somebody makes an improved solid state version. You are lucky you don't have the rally dash -- it has the IVR built into the fuel gauge, so you would have to do some cutting and soldering to replace it. But on the standard dash it is a screw-on.
 
Appreciate the quick response man!
I'll probably order it before digging in.
But once I'm in, is there a way to test everything? Just curious.
Also, I've noticed that recently when I wash my car, water gets into the heater vent and spills all over the driver side floor. Could this be the cause of the problem?
 
Sounds like your cowl drain holes are plugged with debris or you have rust issues in there.
 
Cudascott: how do I get into that section?

Mvh: about testing the gauges once I'm in, I was just wondering if the voltage regulator issue could have possibly shorted the gauges as well. Thanks
 
They are kinda of a pain to get at with the fenders on but can be done by removing the fender splash shields. Here's you a pic of where they are. They are the tunnel shape openings.
 

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cudascott said:
They are kinda of a pain to get at with the fenders on but can be done by removing the fender splash shields. Here's you a pic of where they are. They are the tunnel shape openings.
Click to expand...

Lotsa luck getting 45 years worth of pine needles, leaves and other composted guck out thru those weep holes.

I ended up having to open the heater box and removing the driver's side air box, reach up inside and pull out what I could (without slicing an artery on the sharp edges!). Combination of compressed air & vacuum cleaner to get out more, then go for a drive and let the wind blow 10 lb of crumbs into the car.
Repeat procedure as many times as necessary.

Hopefully, you didn't fry the gauges when the voltage limiter failed.
 
Thanks Cudascott! Nice pic
Thanks oaktree
Poisondart: I don't know man, I love all the stock parts! Keeping it real
 
Richard Ehrenberg did a very good article over at

http://www.allpar.com/history/mopar/electrical2.html

I converted my internal to an external when it wasn't working. The gas gauge is off about 1/4 so eventually I'll have it rebuilt. My factory temp gauge works fine but I also have an aftermarket temp gauge.

Here's a pic during my external regulator installation. In this picture, two of the leads are reversed. Pete In NH, a member here, helped me find it. Probably best to use black for ground, D'oh#-o (and I even have plenty of black wire!) It's difficult to see but the regulator is mounted on a heat sink on the right.

Just follow Richard's info and you'll be fine.
 

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My experience is that when the IVR burns out, it takes the fuel gauge with it (a full 12 volts will fry the gauge). The temp gauge seems to be more resilient. But I have a Barracuda, where the IVR is built into the fuel gauge -- in a Valiant or Dart it's a separate component, so your result may be different.

It just occurred to me that a lot of chargers for small consumer electronics put out 5V DC -- maybe you could use one of those for bench testing.



stillandystill said:
Cudascott: how do I get into that section?

Mvh: about testing the gauges once I'm in, I was just wondering if the voltage regulator issue could have possibly shorted the gauges as well. Thanks
Click to expand...
 
Mvh
Ok cool, I haven't received the ivr yet but should b here any day. Couldn't find fuel gauge online...where should I look?
 
I got the idea from some other here to use D batteries to achieve 6 volts. Should make the gauge read halfway. Also clean all the contacts. I had to get rid of the stamped nuts, and use a standard nuts on the back of the dash to get them to work properly.
 
furyus2 said:
I got the idea from some other here to use D batteries to achieve 6 volts. Should make the gauge read halfway. Also clean all the contacts. I had to get rid of the stamped nuts, and use a standard nuts on the back of the dash to get them to work properly.
Click to expand...

Great idea changing out the nuts. Not a bad idea to also add another good ground to the dash.
 
67Dart273 said:
Uh, no.....................


So far as the nuts I agree, posted this many times
Click to expand...

I may have the volts number incorrect, but I did use the D batteries. Moved the gauge to approximately 1/2 way. This told me the gauges worked. Not how accurate.
 
Right on! You guys have been a biiiiiig help! Gonna try the battery trick to test gauges while inside.
Off topic***
Will a 71 318 intake manifold fit my 72 225? Found a great deal on craigslist to finally super six. Thanks
 
318 is a V8 and definitely will not fit a slant

EDIT: To Super Six it, you'll need to find the slant 2 barrel intake from a FMJ or truck that was equipped with the 2 barrel. Grab the carb and kick down linkage as well.
 
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