Help diagnosing wiper motor speed issue-1978 280z

[misterL]

Hi everyone,

I recently tried to get my 1978 280z inspected, but the wipers were so painfully slow they wouldn't pass it.   I did some reading and ended up removing the motor to diagnose the problem. 

My understanding is that it was likely one of two things:

1. Motor turning too slowly
2. Linkage stuck or too tight

After removing the motor and checking everything out, it seems to me that the motor is moving plenty fast, and the linkage moves very easily by hand as well.  I've uploaded a small video showing the motor speeds here:

Does everything seem normal?  If so, any other ideas on why it's wiping so slow once everything is put back together?

Thanks!

 

[Zed Head]

It's a combination of a weak motor and low voltage at idle RPM, usually.  Try an experiment - turn up your idle speed, or use your foot on the throttle, until the voltmeter shows that the alternator is putting out more than battery voltage.  See if the wiper speed is still slow.

When I had a weak battery and low idle speed, mu wipers would often stop completely at a stop light.  A fully charged battery, better alternator, and 100 extra idle RPM solved the problem.

[misterL]

Thanks for the reply!  I'll try this out and report back.

[SteveJ]

I took the linkage out my 260Z many years ago. I cleaned it thoroughly and lubricated the joints with white lithium grease. I didn't do anything to the motor. The end result is a nice functioning wiper.

[sweatybetty]

loose or corroded connections will cause voltage drop that could be part of the problem also. without the linkage connected, there is no load on the motor, so it will turn normally.

[misterL]

5 hours ago, SteveJ said:

I took the linkage out my 260Z many years ago. I cleaned it thoroughly and lubricated the joints with white lithium grease. I didn't do anything to the motor. The end result is a nice functioning wiper.

Was the linkage hard for you to move by hand before you lubed it?

[SteveJ]

The wipers were painfully slow. I can't remember all of the details. It was many years ago.

[Zed Head]

The motor is so weak and voltage sensitive, and the alternators so close to the edge at idle speed, that every little bit helps.  There are many many wiper motor "upgrade" threads out there.  Even the type of wiper blade probably makes a difference.

[ted66]

I also had painfully slow wipers. Don't Drive in the rain, so I didn't worry about it.  I replaced all my old looking relays with some nicer ones, including the wiper relay. My Wipers work great now- just a thought.

[misterL]

1 hour ago, ted66 said:

I also had painfully slow wipers. Don't Drive in the rain, so I didn't worry about it.  I replaced all my old looking relays with some nicer ones, including the wiper relay. My Wipers work great now- just a thought.

Impressive!  Any more details on what I'm looking at there?

[misterL]

5 hours ago, Zed Head said:

The motor is so weak and voltage sensitive, and the alternators so close to the edge at idle speed, that every little bit helps.  There are many many wiper motor "upgrade" threads out there.  Even the type of wiper blade probably makes a difference.

I read about the Honda wiper motor upgrade... that's a possibility, but I thought it'd be worth trying to get my current system working well enough to at least pass inspection first.    I even saw a thread recommending plenty of RainX to get things moving!

[Zed Head]

I was just making the point about the general weakness of the system.  It's sensitive, it won't brute force its way ahead like my Pathfinder system, which actually bent a wiper arm when I turned them on with a blade frozen to the windshield.  

Once I got all of my components back to their 35+ years ago level of cleanliness and corrosion, and the electrical system up to par, it works fine.