How much current should the wiper motor draw?

[Stevehose]

When I turn my wiper motor on, the voltmeter drops to around 10 or so, indicating a large power draw, is this normal (it's a pretty hefty motor) or should I rebuild or replace? This is without the wipers attached and there is no binding of the linkage, I rebuilt that and it works very smoothly.

 

[Simufly]

I assume you mean engine off and the voltmeter is across the battery?
If so I suggest a new battery.

 

[mulberryworks]

This might not be an excessive power draw, but a bad ground. Years ago I had trouble with a taillight that wouldn't light. The bulb was good and I got 12v at the socket, but the bulb would not light. In that case it was a bad fuse contact that was letting just enough electrons through to show the right voltage, but as soon as a load was applied, the voltage fell to zero and thus no power to the bulb. Bad grounds will work in a similar way. Without a good return path to the battery, the voltage will drop when a load is applied.

I've also seen some wires have bad connections inside the spade lug so even if the lug is clean and the connection to ground firm, there can be resistance. Check with a known good wire directly to the battery and see if the voltage drop still exists. Visual inspection isn't always enough.
I have a thermal camera from FLIR that is helpful to pinpoint things that are hotter or colder than they are supposed to be. About $150 and it connect to my iPhone. Handy little device.

 

[Stevehose]

Will check out connections and grounds. Voltage drop is both with car off and running reading from my dash installed voltmeter.

 

[Simufly]

Will check out connections and grounds. Voltage drop is both with car off and running reading from my dash installed voltmeter.

If you are getting 10volts with the engine running and wiper motor on you have probably have some dodgy wiring somewhere. (Possibly the voltmeter?) Try an accurate digital voltmeter across tha battery terminals and see what happens with the engine running and wipers on. I would expect more than 13.2v with the engine running and not a lot less the 12 with the engine off.

 

[Stevehose]

Ok so with a real volt meter I get 13v this am before starting, 14.4v charging with engine on, wiper motor running it drops to about 14.2 charging and 12.9 engine off. So it appears that my dash volt gauge is not optimally connected, when I installed it I just tapped into a switched wire I found behind the speaker grille, what is the optimal way to wire this, directly from the fuse block?

 

[KHB]

I originally had my voltmeter connected to either the Fuse 5 or 6 circuit and would lose almost a volt just stepping on the brake. With headlights, AC and brake on at idle it was down to 12v (55A alternator). When I pulled out the fuse block to clean the connections I saw there were 2 spare connections on fuse 10 so I hooked up the voltmeter to one of them. It now comes on with the key in the accessory position, but it's rarely in that position anyway. Readings are now about 0.75v higher than it was in the past.

When turning things on to make sure they were working after having the fuse block out, I learned my wipers don't work. Don't know if they were before I took things apart or not as it's been a few years since I ran the motor just to run it. The wipers do run with the washer pump. One of these days I'll get back to figuring that one out.

 

[Stevehose]

Yes thanks I saw that today - the last 16 amp fuse is not used for anything if you don't have a sunroof which I dont. I got tired of digging around in there today so will table this project until cooler weather and accept that my gauge does not read load well.

 

[Mike Goble]

I

Ok so with a real volt meter I get 13v this am before starting, 14.4v charging with engine on, wiper motor running it drops to about 14.2 charging and 12.9 engine off. So it appears that my dash volt gauge is not optimally connected, when I installed it I just tapped into a switched wire I found behind the speaker grille, what is the optimal way to wire this, directly from the fuse block?

I have my voltmeter wired directly to my cigar lighter wire. It's a good heavy duty wire that has no other loads and is live all the time. I have a CS130 alternator and it reads about 14.5v all the time.

 

[Stevehose]

Does this draw enough current to kill the battery over time if the gauge is always reading?

I have my voltmeter wired directly to my cigar lighter wire. It's a good heavy duty wire that has no other loads and is live all the time. I have a CS130 alternator and it reads about 14.5v all the time.

 

[Mike Goble]

Does this draw enough current to kill the battery over time if the gauge is always reading?

It would take a long time. Mine is a D'arsonval meter and draws about 1 milliamp full scale, so to drain a 90 amp/hr battery would take about 90,000 hours - roughly 10 years. Modern cars have a parasitic key-off draw many times this amount for all the electrical devices in the car that need constant power.