Gauges go to max on hills!

[Daved27c]

Sent: 8/14/2004

Hi Guys;

We finally got the Titanic out for a trip this weekend. I had an old problem resurface, which has me(somewhat) concerned. When We start up a big hill, or if I start to push her too hard, all of the gauges start to max out. By this I mean that the oil pressure goes to the max. The temp. gauge goes up, both of which could be because I am pushing it, but I gain a quarter of a tank of gas?? I think it is a problem with the voltage regulator, or the voltage limiter, or something. The problem seems to be worse when I am charging both batteries.(switch on duel). by this I mean that the gauges read higher, than when I have the switch just charging the starting battery. Any thoughts??? 72 chieftain 413, M400

Dave

[MSN Member]

From: Sea Hag
Sent: 8/15/2004

Sounds like you are on the right track . with the voltage regulator or Limiter . as these gauges are voltage sensitive . I would start with the Regulator  first . I'm not sure where the voltage limiter is on the older style dash (pre 73).  - Sea Hag

[Daved27c]

Sent: 8/15/2004

Sea Hag;

Thanks for the reply. I am going to see what the group has to say, before I just start changing parts. I have already replaced the alternator and starter for other reasons.

Dave

[DaveVA78Chieftain]

Sent: 8/15/2004

On that year chassis, the instrument cluster voltage limiter is located inside of the fuel gauge case.  Only the fuel gauge and the temperature gauge use the voltage limiter. The oil and amp gauges do not use the voltage limiter.  So, if all gauges are showing a problem, then it is either a bad ground or the alternator is putting out to high of a voltage.  First thing to do is get a digital voltmeter and connect it to a 12VDC source like a fuse at the chassis fuse panel.  Drive the rig and monitor the readings with the digital volt meter.  Should be between 13.8 and 14.4 volts depending on battery condition and temperature.  All accessories (lights, heater, etc) should be off.

Dave

[denisondc]

Sent: 8/17/2004

I added a ground wire between the metal of the instrument cluster and the frame. I also added a new ground wire -heavy gauge- between the frame and the case of the starter motor. The old ground strap between the back of the tranny and the frame looked scabrous. I think my gauges are more consistent now.

[Daved27c]

Sent: 8/17/2004

Guys;

Thanks for the responses. Dave I will not bother with the voltage limiter, as the problem effects all of the gauges. I will have to try the meter. Denison, did you have gauge issues? I can understand ground problems, but I don't want to start adding if I don't have too. I am going to add some mechanical gauges, as soon as time allows. Maybe we could do this* AT* the NECWJ(2). Kinda be a hands on thing. Keep the guys busy. Yes, I know another shameless plug for the jam, but one has to try. If you are in the Northeast, and like to camp, the NECWJ(2) is for you. Check out the Jamboree board for details, and to sign up.

Dave

[DaveVA78Chieftain]

Sent: 8/18/2004
Dave,
The information I provided before was based on the writeup in the chassis manual.  However, now that I have had a chance to look at the wiring diagrams I am not so sure it is correct as stated.  Obviously with the limiter built into the fuel gauge, it uses it.  The 70-71 and 72 wiring diagrams both indicate the lmiter output ("A" terminal) of the fuel gauge is jumpered to the "A" terminal on both the temp and oil pressure gauges.   That means limiter is used on all 3.  Now, the fuel and temp gauges are thermo-electric gauges.  The oil pressure one is not.  The amp gauge does not use the limiter at all.  So if it to is not indicating correctly when the others are messed up, I am at a loss.  For 72, the drawing indicates there is also a v/limiter capacitor installed on the fuel gauge "I" terminal.  It would used as a filter to reduce the AC ripple voltage by the way it is hooked up.  It would just keep the needle from vibrating though.  The worse on dual vs single battery charge symptom could be attributed to the fact that the regulator bases the charge voltage and current by sensing battery condition.  In dual, it may see the need for more juice so puts out more juice.  That may be why you see the Dual vs single diff.  First, I would simply install a jumper wire from a known good ground connection to a ground connection on your gauge panel.  See if that fixes your problem.  If so, either clean up the ground connections or just install a new ground wire.
Good luck
Dave

[Daved27c]

Sent: 8/18/2004

Dave;

Thanks for taking the time to look that up. When this problem occurs, it does not effect the amp gauge. So I think that means that the voltage limiter could still be a problem. I think I am going to start by taking your advice, and clean up the grounds. If that doesn't cure it, what would you do next? Replace the limiter, or the regulator? Are either of these more likely to have intermittent problems? Now, just thinking into the keyboard. If the voltage regulator was the culprit wouldn't I see the problem in all of the 12v equip? It is not blowing light bulbs, and all of the 12v works fine. I guess this is leading me back to the dash, the grounds, and the limiter. Again thanks.

Dave

[denisondc]

Sent: 8/19/2004

The voltage limiter only supplies the gauges -- the needles so to speak. Though the ammeter is independent, as has been said. All of the light bulbs in the instrument panel and dashboard are ordinary 12v lamps, and get the normal 12 volts, not any regulated volts from that voltage limiter. My gauges always worked okay, aside from having to replace a fuel tank sending unit one year, the oil pressure sending unit another year, the water temp sending unit a few years after that.....
I added the ground wire to my dashboard because I saw definite flickering of the instrument panel lamps at night when I would use the turn signals, brake lights, turning on the heater fan etc. They still did it after I added the ground wire, but it wasn't as noticeable. I also added a new ground wire (2 gauge) from the frame rail over to the casing of the starter.

[DaveVA78Chieftain]

Sent: 8/19/2004

Dave,
Terminology here can be confusing.  You have the alternator and it's associated regulator (battery charging).  You have the voltage limiter (incorporated inside the fuel gauge for pre-74 chassis) for the gauges.  Each has it's own purpose, so don't confuse things.  If ground clean up does not work, read the voltage limiter info at the link I included before.  The troubleshooting info was scanned and uploaded as pic files.

Dave