Temp/Oil gauges not working

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Longgone

Longgone

John/68 Barracuda & Dart
Joined
Jul 12, 2005
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Location
Newport News, Virginia
My oil and temperature gauges are not working in my 68 Barracuda and if you put a test light to their respective wiring the light blinks every few seconds. I went back to the printed circuit and have power coming in to the fuel gauge which feeds the other two. The third terminal on the fuel gauge( not the one that goes to the sending unit) blinks when touched with the test light,same as at each sending unit.The fuel gauge works fine.Could this be the voltage regulator for the gauges or a bi-metal switch in the fuel gauge? What could cause the intermittent power here?
 
Some one out there must have had some experience with this. How do you test the gauge voltage regulator? Is 5 volts the proper voltage?I`ve heard you can make one with parts from Radio Shack.
 
I have read that article in Mopar Muscle and if you look at it I have 12 volts to terminal A and then at terminal B is where I get the intermittent voltage, very weak around 4 volts but not constant.The fuel gauge works fine but the oil and temp are only getting the weak,intermittent voltage.Wouldn`t the fuel gauge be inoperative too if it`s a bad regulator? I haven`t had it apart but I have had the cluster out. It`s presently back in the car.I could imagine the bi-metal strip heating and breaking the connection then cooling and going back causing the blinking but shouldn`t there be a small capacitor that stores this energy, so there can be a constant supply of low voltage for the gauges?
 
Thank you Scott for all of your help,much appreciated.Still if anyone can put their finger on this one,I`d be glad to hear from you. ( Just post what you know)
 
My friend you seem to be betwen a rock & a hard place. This is one of those %&%#@ weard problems. I just got out my 67 -70 good book and checked out your problem comments. Everything you have done with your trouble shooting is correct. I have dealt with the (Voltage Limiter)...known as a regulator before and they don't blow very often, (even after thirty years) although these are not up to snuff as a solid state item. This may not help...but what do ya have to lose...due to your fuel guage working with no problems and it's in between your temp and oil guage electrical run on the cluster....I would only suspect "first" that you have a small ground problem right at your limiter....thats not getting picked up quick enough on the fuel guage (this making it seem that the fuel is OK) First, ensure that the limiter is well insulated between the three probes...5V, 12V & Ground and that each of these probes are touching the curcuit correctly?? In fact...check that your cluster tracks are not broken as well on the back of the cluster. Also you may try to check to see if your main power supply coming into the cluster....from the "connector" is a steady 12V. One problem Ive had in the past is that these dam connector pins get very sloppy and sometimes you have to stick your hand up under the dash and wiggle the connector around while watching your oil light. If in a real bad way and no go...of course try to get a used limiter. Wish I could give you my spares. Good Luck
 
My friend you seem to be betwen a rock & a hard place. This is one of those %&%#@ weard problems. I just got out my 67 -70 good book and checked out your problem comments. Everything you have done with your trouble shooting is correct. I have dealt with the (Voltage Limiter)...known as a regulator before and they don't blow very often, (even after thirty years) although these are not up to snuff as a solid state item. This may not help...but what do ya have to lose...due to your fuel guage working with no problems and it's in between your temp and oil guage electrical run on the cluster....I would only suspect "first" that you have a small ground problem right at your limiter....thats not getting picked up quick enough on the fuel guage (this making it seem that the fuel is OK) First, ensure that the limiter is well insulated between the three probes...5V, 12V & Ground and that each of these probes are touching the curcuit correctly?? In fact...check that your cluster tracks are not broken as well on the back of the cluster. Also you may try to check to see if your main power supply coming into the cluster....from the "connector" is a steady 12V. One problem Ive had in the past is that these dam connector pins get very sloppy and sometimes you have to stick your hand up under the dash and wiggle the connector around while watching your oil light. If in a real bad way and no go...of course try to get a used limiter. Wish I could give you my spares. Good Luck

PS http://www.valiant.org/electrical.html
 
I thought I would post what I`ve found as a benefit to others that might have a similiar problem.I did not have functioning temperature or oil pressure gauges in my 68 Barracuda.A voltmeter showed a pulsating 2.7-4.7 volts to both the sending units.Never the same voltage on each pulse. You could ground each sending unit wire and get the gauges to go all the way up.Voltage was also present( the same) at each terminal on the gauges but they still wouldn`t react.Cluster was grounded well and printed circuit was all good. After removing the gauges from the cluster I used batteries ,1.5 volt each(2 then 3) in series and ran them between the gauge terminals. The temp gauge would go to full on w/3 batteries, whereas the oil would only raise the needle to half way.(4.5 volts should have sent the gauge to full.)While I had everything apart I opened the fuel gauge (the bi-metal switches were all covered in carbon on all gauges)and removed the voltage limiter and replaced it with a 5v chip,heat sink, and capacitor using the spot where the radio noise suppressor bolts down.I plugged the chip right in to the terminals on the back of the fuel gauge.After re-installing the cluster I now have all the gauges functioning(although I`ll need a new oil pressure gauge)and they are rock solid. A solid 5 volts is present at all sending units.These gauges were made to work with a certain amount of tolerance and see the pulses as an average( mine being around 3.7 volts, more than 20% ,enough to affect gauge function). So just because you have a gauge that`ll move to full when you ground the sending wire, it may still be bad. In addition,if you have power to your sending units and gauges make sure it`s a good 5 volts, otherwise you may experience gauge problems/failure as I did.I`d suggest the microchip install to anyone who has a gauge problem or would like to upgrade their cluster.I hope this can help those who are ,or have experienced problems with their gauges. - Longgone
 
Longgone said:
I thought I would post what I`ve found as a benefit to others that might have a similiar problem.I did not have functioning temperature or oil pressure gauges in my 68 Barracuda.A voltmeter showed a pulsating 2.7-4.7 volts to both the sending units.Never the same voltage on each pulse. You could ground each sending unit wire and get the gauges to go all the way up.Voltage was also present( the same) at each terminal on the gauges but they still wouldn`t react.Cluster was grounded well and printed circuit was all good. After removing the gauges from the cluster I used batteries ,1.5 volt each(2 then 3) in series and ran them between the gauge terminals. The temp gauge would go to full on w/3 batteries, whereas the oil would only raise the needle to half way.(4.5 volts should have sent the gauge to full.)While I had everything apart I opened the fuel gauge (the bi-metal switches were all covered in carbon on all gauges)and removed the voltage limiter and replaced it with a 5v chip,heat sink, and capacitor using the spot where the radio noise suppressor bolts down.I plugged the chip right in to the terminals on the back of the fuel gauge.After re-installing the cluster I now have all the gauges functioning(although I`ll need a new oil pressure gauge)and they are rock solid. A solid 5 volts is present at all sending units.These gauges were made to work with a certain amount of tolerance and see the pulses as an average( mine being around 3.7 volts, more than 20% ,enough to affect gauge function). So just because you have a gauge that`ll move to full when you ground the sending wire, it may still be bad. In addition,if you have power to your sending units and gauges make sure it`s a good 5 volts, otherwise you may experience gauge problems/failure as I did.I`d suggest the microchip install to anyone who has a gauge problem or would like to upgrade their cluster.I hope this can help those who are ,or have experienced problems with their gauges. - Longgone
Click to expand...

Well Longgone...Looks like your our expert in the guage department now? Must have been a real :snorting: to track that fault down. Knowledge is good....Live and learn.....Well done.
Jim
 
LOL- While I`m no expert (by far) on this, I can say I have an intimate knowledge of my instrument cluster now.I do hope someone can benefit from what I`ve found and thanks to those who read the post and offered their help.-Longgone
 
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