Instrument panel revision (gauges and panel lights)

[JDxeper]

I have started the process of working on the instrument panel. 1978 Dodge M300 chassis Have pulled the panel, and I am ready to start testing the limiter and the gauges.  http://www.classicwinnebagos.com/forum/index.php?action=gallery;su=user;cat=90;u=28
I want to cut the panel into three section, Right, Center and Left.  This would make it much easier to work with.  Anyone see any reason why not?

[JDxeper]

Removed the voltage limiter.  Put the multimeter to in and it was wild ranged from 0.5 volts to 7.0 volts.  Held the voltage for 1/10 of a second. or less.  Now in the process of rebuilding limiter or replace.  Then I'll start the process of checking gauges.

[denisondc]

The way the mopar voltage limiter works is by opening and closing its contacts, so the measured output voltage would either be zero or twelve - if your VOM was quick enough to measure, but the contacts should be closed and you would be measuring 12 volts 'out' about 5/12ths of the time. I think the typical cycling time is a couple of times a second.  This drives my digital VOM nuts, and my analog VOM needles bobbles back and forth.
  The 'limiter' does its job in time-division fashion, not by regulating to an intermediate voltage.  The gauges work okay this way, because they respond slowly; as they work by the heating of a nichrome wire wrapped around their bimetallic pointer. You can see how slow they respond when you turn the ignition off.  They dont just drop back to rest, they creep back.   I know one of our members made up a replacement regulator, using an LM305  5 volt semiconductor regulator.  He used a heat sink, since the current draw is enough to overheat an LM305 that isnt cooled somehow.  It might have been an LM306 that he used; I forget.

The way I made my inst. panel easier to work on was to redo the bolts holding the seat post down.  Now I have captive nuts under the floor.  i can remove the seat, unbolt the seat post, and have a flat carpeted area on which to lie flat on my back while working on the 'rats nest' of wiring.

[DaveVA78Chieftain]

JD,
Here is the the ALPAR website regarding gauges on Mopar vehicles.
http://www.allpar.com/history/mopar/electrical2.html

It includes the digital regulator conversion Denison reffered to.

As long as you do not cut the Printed circuit board (PCB), I do not see any reason why you cannot cut the dash into 3 sections.  It's more a cosmetic issue than anything.

Note to all: Asd shown in his pictures (link above), JD has the new style dash (74 and later).  The old style dash (pre-74) does not use a PCB.  I cannot access it from this computer, however there is a document in the members area under Tests and Test Equipment that also talks about guages (includes pictures).  It is oriented towards the old style dash (pre-74) that Denison is reffering to.

Dave

[JDxeper]

The chip regulator that I have is a 7805 5V, 1.5 amp from Radio Shack and a heat sink.
I'm going to try to mount it all on or on  the old regulator so it will just plug in the printed circuit.  I think I remember that Pinballlarry re did his panel a couple of years ago.  When I get it don I try to post pics
JD

[JDxeper]

After doing a little more reading, the limiter works on pulses, 2 every second. Not steady  current like Dave D said.  Anyhow DaveVACheftain, is the orange wire 52A the 12 volt feed to the limiter? When I check the input side with ignition on I have nothing on my meter.  On my diagram it looks like that's the one that feeds the input side from the fuse panel.
Thanks "Daves" for your input.

[DaveVA78Chieftain]

Page GRP-08-PG-77 of your chassis manual.
As shown in this drawing, the connector for the PCB is shown off to the left of the panel.
The regulator is denoted on the drawing by the GND/12 V/5V square connectors.
I show the circuit below (red=12VDC; Green=5VDC; Turq=GND.



A choke is shown included in the 12VDC portion of the circuit.  Thats the white boxey thing to the left of the regulator in your pic below



Dave

[JDxeper]

Help i??

OK Dave need some more help.  in the picture between the choke and the regulator are two spade or posts sticking up one is grnd and the other connects to the 12v printed circuit.  The wire were not plugged into the board after I got it out to see behind it.  I found a 12v hot when the ignition is on. but can't find the ground. 
1.  Is the white 12 v wire the one that goes on the 12v spade on the circuit board.  This wire comes from the MOM switch.
2. Where's the ground? or can I make a new one to the frame?

[JDxeper]

head light switch replacement  BWD  part no S426
blower control switch  replacement  BWD  part no BL5

[DaveVA78Chieftain]

JD,
Please notice that wiring drawing is based based on the picture.  I sure hope this gives you the information your looking for.
In the picture
Bottom pin: Ground (White/Blk stripe)
next pin up: 12VDC from fuse panel (Black/White stipe)
next pin up: Oil Pressure sender (White)
Next pin up: Fuel sender (Lt Blue)
(Winnebago may have modified some things to for fuel gauge wiring. )

[DaveVA78Chieftain]

I believe the extra posts were for the aux fuel gauge if one was ordered.  Winnebago normally modified the circuit so the tank select switch changed both the tank and the input to the gauge rather than installing a separate aux fuel gauge.

Dave

[JDxeper]

I will have to study the diagram.  I was looking for where the 12v input was from and to.
When I turn the key on the panel is dead. i??

[JDxeper]

I will have to study the diagram.  I was looking for where the 12v input was from and to.
When I turn the key on the panel is dead. i??

Rechecked your diagram and that exactly what I wanted , 1st pin grnd, 2nd pin 12v input to panel.  multimeter shows 11.5 volts.  now on to a couple of hanging dead end wires.
thanks much

[JDxeper]

installed a new 5 volt regulator.  I think I shorted the one I built.  It did not test correctly.  Purchased a new one.  http://www.kansasselectproducts.com/servlet/the-10/5V-INSTRUMENT-VOLTAGE-REGULATOR/Detail   and put it in.  The oil pressure gauge works fine, fuel still shows half full and empty. water temp also works.  amp meter does not work. Will look into them again later.

A new head light switch cured most of the panel light problems.  Have panel lights on most everything..http://www.classicwinnebagos.com/forum/index.php?action=gallery;su=user;cat=90;u=28   The Instrument panel is now in three parts and is easy to get in and out.  Got a little sloppy on the right hand lower cut .  Drill 4 new holes and put it back in with stainless screws and square nuts.

[DaveVA78Chieftain]

JD,
Note: To anyone reading this post, this information for the ampmeter only applies to the new style dash (74 up).  The old style dash (pre 74) had the alternator B+ wire routed to the ampmeter then went to the starter relay and the shunt is built into the ampmeter itself.   Aftermarket gauges, like Stewart Warner, also have a shunt built into them which is why you also connect them in series with the alternator.

The ampmeter is actually a milli-voltmeter that reads a voltage across a shunt wire.  It is feed by the red and black wires coming into the center of the other connector (black one on right side of this picture).


Those 2 wires trace back and connect as shown below (Dash ampmeter). On the chassis wiring diagram:
B1-18RE (Red 18 gauge wire)
A1-18BK (Black 18 gauge wire)
The fact they are 18 gauge tells you there is very little current drawn.  If your voltmeter can read millivolts, you should be able to see a voltage across those 2 pins.  Most likely less than 75mv.  The pins on the dash PCB are delicate.  Mine broke off and I had to repair them (heat and corrosion).



The ampmeter (millivolt meter) is measuring the voltage drop across the 2 wire point connections (A20A-10BK wire).  Here is a description of how this works: http://www.reuk.co.uk/Make-a-Shunt-Resistor.htm
Dave