VDo gauges sensitive to voltage fluctuations?

[Oilburner]

Driving the 109, doing about 75 mph, the temperature always fluctuates between 210 and 215 (215 degree tstat), the oil pressure sits at 3/4, and the voltage sits at 13.8 exactly. It's always like this.

So, I am driving along a few days ago, and I look at the voltage gauge, and it reads 13.3. The temp gauge reads 220 (maxed out) and the oil pressure is lower than should be expected. I pull over and check the rad hose, no pressure in system. I crack the rad cap, it is a little low (no overflow so it belches a little coolant every once in a while - If anyone has a series III overflow tank with bracket I would really like to buy it off of you). I top it up, check the oil (a little low but still in the safe zone), and I get back in.

The problem continues. Gauges still behaving badly. I drive to the nearest gas station, and check the coolant again, check the oil again, and everything is cool. I get back in, immediately on startup the voltage goes to 14 and everything is fine.

I drive on for an hour, shut it off, and restart, the same problem reappears. At this point I am pretty sure that I don't have an overheating or low oil pressure problem, so I ignore my gauges on the way home.

I am wondering if anyone has ever experienced some wonky readings from VDO gauges due to voltage fluctuations. I think I may have an intermittent bad reg. in the alternator, maybe a cooked diode. The alt is a Leece Neville 200A bus alt and the voltage does not usually drop unless I use the winch for 3-4 minutes.

 

[Michael Slade]

I have a 4-way marine guage in my CrewCab and I notice that the voltometer section seems to fluctuate. I have a GPS that when plugged into the vehicles power supply, it will tell me the status of the power system in volts. I see that the GPS doesn't fluctuate wildly, but the VDO 4-way guage does. I gave up trying to figure it out because I realize that it's not the system and probably the guage.

Driving the 109, doing about 75 mph, the temperature always fluctuates between 210 and 215 (215 degree tstat), the oil pressure sits at 3/4, and the voltage sits at 13.8 exactly. It's always like this.

So, I am driving along a few days ago, and I look at the voltage gauge, and it reads 13.3. The temp gauge reads 220 (maxed out) and the oil pressure is lower than should be expected. I pull over and check the rad hose, no pressure in system. I crack the rad cap, it is a little low (no overflow so it belches a little coolant every once in a while - If anyone has a series III overflow tank with bracket I would really like to buy it off of you). I top it up, check the oil (a little low but still in the safe zone), and I get back in.

The problem continues. Gauges still behaving badly. I drive to the nearest gas station, and check the coolant again, check the oil again, and everything is cool. I get back in, immediately on startup the voltage goes to 14 and everything is fine.

I drive on for an hour, shut it off, and restart, the same problem reappears. At this point I am pretty sure that I don't have an overheating or low oil pressure problem, so I ignore my gauges on the way home.

I am wondering if anyone has ever experienced some wonky readings from VDO gauges due to voltage fluctuations. I think I may have an intermittent bad reg. in the alternator, maybe a cooked diode. The alt is a Leece Neville 200A bus alt and the voltage does not usually drop unless I use the winch for 3-4 minutes.

 

[Carlyle]

My voltmeter fluctuates a little as well, especially when I run extra things like my seat heaters or Hotshot windshield cleaner. If all the gauges are fluctuating I wonder if it may be a grounding issue? Then again I'm not an electrician. A low voltmeter helped me diagnose an impending alternator demise a couple months ago...

 

[James86004]

Next time it happens, stop and put a DMM across the battery and compare the readings.

 

[revor]

Used to see this in Jeep CJ's if the instument panel voltage stabilizer was bad, gauges would go crazy though, not incremental wierdness. I would think that VDO's would be internally stabilized..
Never saw a VDO do anything bad either in my Porsche's or my FJ40.

 

[kellymoe]

I have a 4-way marine guage in my CrewCab and I notice that the voltometer section seems to fluctuate. I have a GPS that when plugged into the vehicles power supply, it will tell me the status of the power system in volts. I see that the GPS doesn't fluctuate wildly, but the VDO 4-way guage does. I gave up trying to figure it out because I realize that it's not the system and probably the guage.

A side benefit of my HAM radio is that it also gives me volt read out.