D&M dash meter

[Dogsled]

I've had a D&M dash multi meter for volts/gears/ambient temps. I recently put in a Simpro alternator (80amp) and a yuhasa battery and am getting way different readings with a multi-meter. The meter of the battery and the D&M are volts apart.....this thing saved me several times when my alt has gone out. Why would the two read so different. Anybody got any knowledge of how the D&M gets its readings and WHY would they be so different

[PastoT]

Never used this meter and don't have a 97 GW but electrically speaking if the D&M is not sampling voltage straight from the battery I would expect some variance, still "volts" is unacceptably large. The further away from the battery connector that the meter is hooked in, the more aged and potentially dirty, loose or corroded contacts exist to impact the voltage reading. I'd use your VOM to check the voltage where it the meter is connected and see if the difference is the same; if so I'd start cleaning and tightening connections or relocating the connection to the battery wires themselves. Perhaps changing Alternator & Battery left some questionable connection incident to the mx work.

[CMReynolds1]

I would measure the resistance on the line (Ohms) from beginning to end of the wire. Then clean connections and expect to see a drop in ohms, just a thought. Your suggestion on the voltage is necessary too. If I was doing it, I would do both.

[Dogsled]

I might contact D&M for a schematic. Bad thing is i just had all the plastic off putting in some new lighting wiring and installing a high voltage alternator. There's alot of wires coming out of the plug in so knowing if a wire is direct or indirectly hooked to the hot is gonna be hard to locate without tracing the route of each wire and the cluster f*** harness running thru a wing is bad enough when you know the color codes to start with. How the heck does this thing know the temperature of the air when the bike is moving. I've never seen anything that would be capable of reading this. Another polastic body teardown this year will call for a stick dynamite and blow this bike to ****. I can only tolerate this crap once a year......3 hours to get to the problem, 5 minutes to fix and 3 hours back together. (I know that's an exaggeration but it's startin to feel that way)

This wide voltage range of 3 volts is pretty substantial, I was surprised. It's a digital readout and has always been accurat in the past.......so advice it to start cleaning huh???????

Well thanks for confirming what I didn't want to hear, ride safe........

[newday777]

You haven't said which meter was reading higher.

The Simpro could be at fault as they are long out of production and were known for having problems. Take it to an alternator repair shop and have it tested.

[Dogsled]

I bought this one particularly........Compufires have more problems than a properly rebuilt Simpro. Ken Heming built this one for me. Completely rebuilt, this is one sweet alternator. The only reason I didn't go with Lactrical was too much wiring changes and I have a Heming OEM for back-up. The Simpro was plug and play. Actually that may be a mis-statment, compufires have more problems prolly cause there are more of them out there.

[Bluewaterhooker0]

Dogsled,
Your initial post indicated you had installed a new alternator and battery. Your follow-up post indicated you had also installed some new lighting wiring. As any new lights added will create new voltage drops in the circuits, I would start by looking at your new wiring as the possible culprit. I tap my voltmeter off of the wire that feeds my left side marker light. I have a .7v drop at that point, compared to the battery direct. It was easy to install that way, and I just add .7v to my digital meter for a correct reading. If I were to add any other lights to that circuit, I am sure that my .7v difference would change to a higher number. The smaller wires will show a greater drop than a larger wire. Part of the voltage drop is actually the wiring, itself.

[WingAdmin]

It could be due to any of several reasons.

If the dash meter is hooked up to existing ignition wiring rather than directly to the battery, it will be reading voltage drops that occur in every connector and switch in between it and the battery, along with any voltage drops occurring due to the length of the wire runs, degraded crimps/joints in the harness, etc. The easiest way to know is to take your multimeter and measure the same wires that are feeding your dash meter, and see if there is a difference.

It could be due to a miscalibrated multimeter - if you plug your multimeter into a known, regulated voltage, is it reading high?

It could be due to a sensitivity of the dash meter (or the multimeter) to noise. I had an inexpensive meter once years ago that would measure perfectly when the bike was shut off, but as soon as you started it up, it would pick up the noise introduced onto the voltage bus by the stator, and interpret the tiny spikes and waves as constant voltage, with the result that it would read several volts high. A capacitor on the meter lines fixed this problem.

It could be a problem with the dash meter itself.

More important than absolute voltage is identifying a CHANGE in voltage, and it sounds like your dash meter has done just this for you. If the bike runs normally and your dash meter shows 9 volts, even though you know it is obviously wrong, you at least know that when it shows 9 volts, things are fine. If it suddenly drops to 7 volts, you know you have a problem.

[Dogsled]

Yeah I guess that's what i'm gonna have to do.. I had 2 alts go bad and it dropped tovirtually nothing. and I knew I was in trouble. There's a bunch of wires in the plug and I don't know how it wires up when installed new so don't know where it gets it power source from. It just blends into the wiring goin under the radio. I e-mailed Daves cycle, I never heard of them, they're a pretty big Wing part store it seems. They were the only one in Google showing this item. Sounds like it's thier exclusive product.. They got the direct line to China....

Thank s to everyone. If someone reads this down the road and has paperwork on it , a PM would be nice so I may get some info. With my smooth touch with wiring, I shouls be able to burn some part of the harness up once I get my hands in there

[Dogsled]

I told Dave I would send a shout out for his super response on the D&M meter....They sell alot of bike parts. Look them up for some different things and compare some prices.....I live in Ohio and favor buying out of state on large enough orders to get free shipping and not having to pay taxes. I'll keep them in mind for sure. Tax doesn't take long to get a guy to turn his head from buying from his own State. So if you live in Ohio and order from a store in Ohio, you're gonna pay the thieves in govt. give them a look see, very quick serive and response.... that's davescyclesupply.com