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Instrument Cluster Voltage Regulator

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Rebuilt my cluster a while back and tested all gages with a 3V battery test setup.  All gages seemed to work fine.  I changed out the voltage regulator with a new one because it seemed like the obvious thing to do during the rebuild.  I installed the cluster and gages are not working.  All other functions like lights are working fine.  After some troubleshooting, I tested the voltage regulator and it seems to be putting out a constant 5V instead of a pulsing 5V.  My gages now seem to be toast when doing a continuity test. Does it seem feasible the constant 5 volts would have fried the gages and does it sound reasonalble the regulator was defective new and did not have the pulsing function?  Is there a voltage regulator that uses and constant 5V and could have been a mixup at the parts store?  Any help would be greatly appreciated.

 

Rick

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A constant 5V source for the gauges should not blow the gauges.  A CVR should not put out a constant 5V if it is the old style CVR; the newer electronic ones will, though.

 

I'd remove the CVR and re-test the gauges.  If all are blown, then something was amiss with the circuitry would be my guess.

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Your voltage regulator is fine.  The original regulators operated on the principle of taking 12v input and rapidly switching on-and-off to provide a 5 v output.  Simple, mechanical, and cheap.  Unfortunately anything mechanical can and will fail.  With the development of electronic components since the 60's, it is cheaper now to make a solid state electronic regulator that simply emits 5v constantly, from a 12v feed.  Simple, cheap, reliable solid state electronics.

 

Why do you think your gauges are toast - as in, what is happening exactly under what conditions.?

 

There are a number of ways to test your gauges. I have a post in here somewhere detailing how to make a cheap testing tool, just for the gauges, checking their accuracy and range.  Key to this is providing the correct 5V power.  This should be done with the regulator from your instrument panel.  This ensures your gauges and regulator work properly together.  It is probably worth trying that now.

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Thanks for the info guys.  My fuel gage and temp gage show no continuity across the rear terminals.  That implies to me the connection inside has been broken.  The oil pressure and alt gage show continuity but are behaving odd when using my 3volt battery test.  For a gage whose normal position is in the middle like the alt, what ohm reading will make it go each way?

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OK...let's clear up some misconceptions.  You can test that the gauges CAN function by putting a 3 V battery across the contacts, but where the needle goes depends.  The ammeter gauge should peg with 3V battery, so only apply the voltage briefly. 

 

With a 5V power supply, the needle position is a function of the resistance of the (oil, temperature, or fuel) sending unit.  Normally, the resistance of the sending unit itself is about 73 ohms, and the gauge would sit at the far left side.  When the sending unit has maximum readings, its resistance is about 13 ohms and the gauge will peg to the right. 

 

The gauge itself should have continuity between the two posts of something low, probably a couple of ohms or less.  If you are reading kilo or megaohms, yeah, your gauge is toast.  Make sure your multimeter is set up correctly for measuring resistance.  I've seen too many people set the multimeter to DC voltage to measure resistance and read 0.0 and think everything is fine!  Don't forget to disconnect the dash cluster connector when making readings, as the multimeter can measure what's hooked up to those posts and bias the results. 

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Update on my gage issues. Rusty posts provided bad continuity readings. Ended up Gage's were not fried. Someone had mentioned posts touching housing of cluster. That ended up being the problem causing them to ground out. Thanks to everyone for their help.

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I seem to have similar issues: my gauges either don't work or peg when connected. I recently created a solid state voltage regulator(I used the housing from the old unit) to eliminate any issues (I've gone through three of the replacements now). When mounting my gauges carefully in the notched openings, I notice continuity between the posts and ground and tried everything to isolate them from the housing. Nothing has worked so I want to confirm that there should be an "open" reading between the gauge posts and ground. I get no response from my multimeter when measuring ohms but it reads 1503-ish when I check for continuity. To test my meter by touching the negative and positive probes together, I get 005 in the continuity setting and 25 ohms of resistance (cheap unit). Is there an insulator that is missing just under the housing to isolate the gauges?

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On 2/7/2020 at 7:07 PM, scclark said:

I seem to have similar issues: my gauges either don't work or peg when connected. I recently created a solid state voltage regulator(I used the housing from the old unit) to eliminate any issues (I've gone through three of the replacements now). When mounting my gauges carefully in the notched openings, I notice continuity between the posts and ground and tried everything to isolate them from the housing. Nothing has worked so I want to confirm that there should be an "open" reading between the gauge posts and ground. I get no response from my multimeter when measuring ohms but it reads 1503-ish when I check for continuity. To test my meter by touching the negative and positive probes together, I get 005 in the continuity setting and 25 ohms of resistance (cheap unit). Is there an insulator that is missing just under the housing to isolate the gauges?

There is an insulator that goes over both posts between the circuit board and housing. Then there is a plastic insulator that covers post after assembly. 

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On 2/7/2020 at 6:07 PM, scclark said:

I seem to have similar issues: my gauges either don't work or peg when connected. I recently created a solid state voltage regulator(I used the housing from the old unit) to eliminate any issues (I've gone through three of the replacements now). When mounting my gauges carefully in the notched openings, I notice continuity between the posts and ground and tried everything to isolate them from the housing. Nothing has worked so I want to confirm that there should be an "open" reading between the gauge posts and ground. I get no response from my multimeter when measuring ohms but it reads 1503-ish when I check for continuity. To test my meter by touching the negative and positive probes together, I get 005 in the continuity setting and 25 ohms of resistance (cheap unit). Is there an insulator that is missing just under the housing to isolate the gauges?

Don't use the continuity setting: it simply is not accurate.  Yes, there should be an open reading between any of the gauge posts and ground.  When testing for resistance, set the meter to 200 kilo-ohms or 2 megaohms and you should see something other than 0.00.  If you do see 0.00, drop down to 2 kilo-ohms and try again.  You should see something along the lines of 10 kiloo-ohms or higher.  If one of the posts is grounded, you'll see either something along the order of 1 ohm or 13 ohms, depending upon which post is truly grounded.  

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