In-line voltmeter on dash? Suggestions?

[joehahn]

My alternator light has never worked since I have owned car. I have never had a problem and I only really get nervous when I read one of those posts by Warren wherein he says "all your charging runs through that light!". Something is obviously screwy with mine and I would like to have an accurate reading of how the battery is doing.

Recently in the cold weather when I hit brakes real fast or turn on lights my radio will cut off which means not enough juice is floating around the system (I think). I vaguely remember posts about buying a simple voltage meter and putting in-line pretty much anywhere (like cig lighter line, etc). Is that true? Any other good places? Any ideas where to get? I searched archives but nothing really came up (bad search terms).

Thank you,

Joe 68 L


[This message has been edited by joehahn (edited 11-07-2001).]

[RoninLB]

I use aircraft grade gauges. The 6 exh. temp. probes that will be installed with SSI will use a small engine analyzer mounted on console it wll replace casette tape storage. You can look in Aircraft Spruce........www.aircraft-spruce.com and info@aircraft-spruce.com There are others if this tickles you. The volt meters are top quality and beautiful. View the 4 in 1 set up. A class act.

[stormcrow]

Joe,

That doesn't sound like a charging problem. If your radio went off when you turned on your lights then you have a problem elsewhere.

If your battery was that low to cause your radio to go off, then your engine wouldn't run either. Don't ask how I know.

To check if your system is charging, start the engine, turn your blinker on and time the flash, then turn your lights on and check to see if the flasher slows down. If it does, then there may be a charging problem.

Another check is to turn your headlights on and step on your brakes. Again, if your headlights go real dim then there is a problem, but if they stay bright, then you have an electrical connection problem.

An amper meter would be the correct way to see if your alternator is charging. By using an amper meter you will actually see how many amps your alternator is putting out with and without a load on it. Otherwise, you are just guessing.

Steve

[RoninLB]

Stormcrow....you opened up a debate. Let someone else do the work. What you said does sound logical. Good luck on this one.

[jc]

I've got a voltmeter built into my radar detector. Under normal operation if no bogeys detected the display will show voltage level. Plugs into cigarette lighter. Gives me peace of mind at a glance that my system is charging.

Cheers,
jeff

[joehahn]

Thanks fellas. And, Steve, I am ALWAYS guessing!

[Early_S_Man]

Joe,

The current I was referring to going through the warning bulb is called 'pre-excitation' current, and it sort-of 'primes the pump' to use the old water analogy. And, in the context I was using that current through the bulb ... if the bulb is burned out, or if the slip-ring brushes are worn-out, there won't be any pre-excitation current, and the alternator never generates the moving magnetic field in the rotor windings, so the output is zero!

A Voltmeter on the dash or console is a good idea, and provides plenty of information to judge the health of the electrical system, but you must be familiar enough to know what different Voltage levels will be under 'normal' circumstances, and what the warning 'signs' are for alternator/regulator/battery problems that need attention!

An 'expanded scale' Voltmeter like the VDO reads from about 10-20 Volts ... not the ideal range (11-16 Volts would be perfect) but adequate for the job. The one on the right, below, is the 'cockpit-series' VDO that Pelican sells.



A better choice in my opinion (but a more difficult installation) would be an inexpensive $20 digital panel meter with 3-1/3 digits and scaling resistors to give a 0-19.99 Volt range.

[Joeaksa]

Warren is correct that its nice to see what is going on WHILE you are driving.

Two years ago my alternator started to puke. I noticed that the headlights were going from normal intensity to a lot brighter, without my touching the highbeam switch. Turns out that the alternator was going from 14 volts to 16 or so from time to time and the lights were showing the increase in voltage. I do not want to think what the DME computer was saying about this increase in jolts.

To help figure out what was going on I hooked up a digital VOM inside the car. It told me right away what the problem was, but I liked the idea of watching the voltage while I was driving. You can tell a lot about the charging system this way.

I found this gauge at Fry's electronics two years ago. It was a cigar lighter type gauge and worked fine for a while. After a bit I got tired of looking at the center of the car to check the voltage and took it apart. Now it is attached to my tachometer and in the direct line of sight. It also covers up that worthless "shift gauge" that the factory put in the mid-80's cars. Yes I know that the wiring looks like hell but it was a temp installation... two years ago!

Works great and tells me the condition of my charging system at all times. Only problem is that the company making these has stopped producing them and I have not been able to find any more of them nor something even close. I would love to have something more sanitary and professional looking but have not found any other gauges like this in two years of searching.

[joehahn]

Joe, that is EXACTLY what I want. I am assuming you can splice into pretty much any hot and ground? What is Fry's?

[jabb]

Joe:

Anything that is hot while the car is running you can tap into...

[Joeaksa]

Joe,

I spliced into a positive lead on one of my instruments and the ground wire on the same instrument. It is now reading battery voltage with the key on, and the motor off, in the picture. When running it goes from 14.1 to 14.8 or so and immediately shows the system state when I turn anything on in the car.

Fry's Electronics is a chain of stores, mostly in Texas and the West. Do not waste your time looking there, been there and done that. They ran out of them a year ago. Also do not waste your time contacting Whistler, who made this gauge, as they are not making nor stocking any of them! Already been there!

My next choice is to go to some supplier in Japan, Taiwan or the like. I have looked on the internet and so far no luck. This one was a "plug in the cigar lighter" version that I "modified" to hard wire into the system, so lets find something that is close and make it work.

If you find one like this, or even anywhere close, PLEASE let all of us know. I have even taken a couple of cheap digital VOM's apart to make a nicer looking unit, but have not been able to get what I want.

This one still works but several of my friends also want one, and so the search continues. I look everytime I go to an electonics store but have not found anything yet that will replace the one shown in the photo! It sure is nice so lets all keep our eyes open and find one somewhere!

JoeA

[MBAtarga]

A quick search on yahoo turned up something. What about
the EMV 1200 from Lascar Electronics

[Joeaksa]

Mark,

Good Work! I tried Yahoo and Excite months ago and came up with lots of BS but this unit looks nice. This unit is a bit smaller than mine so will fit in the front of the tach.

This gauge does have a "stud" type of mounting and that would have to be removed before mounting unless you wanted to drill a hole in your dash somewhere and mount it this way.

Next question is on lighting. The one I have is backlit, which is nice at night but this is not mandatory. As well I would mask off the display portion and paint the rest of the gauge flat black so it does not stand out so much. I have emailed Lascar about lighting, black case and no stud mount and will get back to you guys when they let me know what they have.

The key is to be narrow enough to not block off the idle and high end of the tach if you are going to mount it to the face of the gauge. I used a small dab of a glue gun to attach mine. When needed I can just pry it off. Tried double sided tape and it does not last.

I am going to contact them and get one to start, then if it looks nice will then post it and we can buy over 50 of them and get a good price.

Thanks!

Joe

[Early_S_Man]

The only problem with that particular LCD meter is that the accuracy is not too good ... the SP100 is an LED unit at a higher $40 price that can be read at night, and has 0.1% accuracy.

http://www.lascarelectronics.com/products.cfm?STOCKNO=SP%20100&CFID=35578&CFTOKEN=60812033

[joehahn]

As usual, this has been informative and I again thank everyone.

Warren, sorry to spring a question from a question but do you have any ideas why my dash light doesn't work? It's not bulb as I have tried replacing w/good one. No charging problems in 2 years with same battery too????

[Early_S_Man]

Joe H. ...

My best guess is tyhat something has come loose inside the gauge and is blocking the light from the bulb. I have seen that happen.

[Joeaksa]

Joe,

My electronics knowledge is not the best but I seem to remember that the idiot charging light is triggered by one of the diodes in the alternator.

I seem to remember hearing someone saying that they had an alternator go out but the idiot light did not go on when it failed. I remember he told me that the particular diode that turns on the "no charge" light was still good, while the others went bad, causing the alternator to fail.

Not sure if this is possible or true, but is one possibility. Have you had your alternator check out by a good shop lately?

Warren,

I looked at the gauge and it says that its range is 200mV. 200 milivolts... will it take 12-16 volts without frying and would the display go this high? Been years since my electronics class but thought that this is bit much?

Thx,

JA

[joehahn]

....hell no! I am not taking that out, are you kidding me? As you KNOW since you have helped me in the past, when I start poking around I tend screw things up worse than they already are.

If it aint broke don't fix it! In the instant case I'll say if it is moderately o.k. and not inhibiting the drivability of the car...I aint touchin it!

[Early_S_Man]

JA,

The 'scaling' resistors I mentioned earlier about the panel meter being a 'bit' more challenging to install ... are explained along with the traces to be cut to illuminate the proper decimal point are all explained in the four-page data sheet at:

http://www.lascarelectronics.com/data/pdf/SP%20100.pdf

The suggested scaling resistors have to be purchased separately and soldered onto the board ... a 1 megOhm and 10K resistor are needed to scale the meter for a 20.00 Volt range. Actually a Voltage divider, 20 Volts applied across the 1,010,000 Ohms ... is reduced to 0.200 Volts accross the 10,000 Ohm scaling resistor at the input terminals of the meter.

[MBAtarga]

Warren,
That 0.1% accuracy won't last long when you use a set of 10% tolerence resistors - I guess you could throw in a potentiometer. Also, the supply voltage for the LED version is 5V, meaning a voltage regulator would also be required. The LCD version would operate off the normal +12V battery.