{Chrysler 300} Gauge Limiter/ gauges

[John Grady <jkg@xxxxxxxxxxxxxxxxx>]

Kind of normal situation Allyn  , they are inherently very imprecise things .
 Another regulator will probably do nothing or all may go slightly higher or lower . If gauges are on the scale and come up at all to middle ( not top) it is working . A defective regulator generally pegs them ( usually due to no ground of gauge mount, not regulator defect — that stock ground wire jumper there is crucial stuff— if no ground , the regulator does not cycle on and off , 12 v steady comes out) .. I solder that to frame now , — a screw  into plastic behind the metal for  holding ground lug is a pretty poor design  
Once pegged like that,  the little heater coil inside can burn —gauge is often junk if that happens . ( depends where sensor ohms was at the time) 
You can see them all rise from cold at turn on , in a few small steps as regulator works by pulsing on and off . Don’t be tempted to adjust gauges . Two adjustments interact it rapidly becomes a can of worms , non linear result .  Did that mistake long ago . Taking them in and out rapidly gets old . 
Most important is the fuel gauge — not those others . Others are just relative you get used to it and note a change if problems .

Fuel gauges that are actually  in very good shape , but with the new reproduction senders are notoriously inaccurate  —it is sender not gauge that is wrong , work the float in your hand outside the tank and bend float wire slightly etc to try to get E somewhere near right , F does not matter much .  Try to clean and use old sender , do not ever bend the little sliding electric contact arm inside it , it will tear up the winding if you try to make it “ touch better” . Ford still sells the brass tanks . 

People change to electronic regulators ( I have done that ) . The switching action of stock uses the  % on time to average the 12 v to about 5.5 . So on about half the time , But a meter reads 12 on and off not 5.5 . Cant “ check” it is correct . on and off cycle about 1 per second means working ok. 

You can check individual gauges on a bench with a 6 v “ lantern battery “ should go to  full scale . One wire to gauge power , one to S terminal 

Electronic regulator IC come in steady 5 and 6 , it needs hand built circuitry , a heat sink behind speedo etc but 5 too low and 6 too high in my experience ( trying to get fuel E right).

There are adjustable electronic ones ( more circuitry )I  have not done that but if I encounter a bad on off in future might try one . You select resistors to set them 
Any regulator change though (as you may think “good to drop temp “) will drop E too and it will read E with a quarter tank or other way round . Much worse problem . 

After years of messing , i leave it alone now. Nature of the beast — but you should try to get E right .

 As I have a few  cars I tend to leave a sticky in the  car advising me about E . You can run out above E or it only takes 14 gal to F yet on E , especially with reproduction senders ; dropping below E line as most do further complicates all this . 

If really one is way out ( typically due to a new temp sender ( keep your old one !) you can add ~ 10-30 ohms 2 watts resistor in series with gauge wire to drop any one gauge , but C will then be wrong , does not matter , but E sure does .  

Left alone and all original stock parts they are ok . Not perfect but ok .
Hope this helps , just my own experience John g


Sent from my iPhone not by choice 

On 26 Sep 2021, at 9:35 pm, 'Matt Allyn' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:

Both the Oil Pressure Gauge & the Temperature Gauge tend to run on the far right (High) position.
The motor is running nice & cool; as proven by my thermal temp. gauge.

And so…
I suspect the Voltage Limiter that lives within the Oil Pressure Gauge is faulty.
Is there a way to test it BEFORE pulling it out?

And…
If I were to pull 1 or both gauges….
I can still operate the car; right?

Thanks!
Matt Allyn

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