M38A1 - vacuum wipers - why are they so slow

[pduske]

Hi fellows,

why are the wipers on my screen so slow / weak in motion?

- I do not have broken vent lines
- the fittings are tightly bolted
- my vacuum pump seems to be fine

What could be the reason?

Is a common "workaround" to reduce the diameters of the other ventlines (to distributor etc) to prevent too much vacuum volume to "bleed" away?

I appreciate your advice

Philipp

[wesk]

- my vacuum pump seems to be fine

And the vacuum reading on a vacuum gage at the wiper motor on/off valve is?

Generally there are two causes for slow vacuum wipers: 1 - Low vacuum, Minimum readings are 10" at 200 RPM and 12" at 1500 RPM, 2 - Worn out flapper inside wiper motor or contamination of the paddle area with dirt or grease that causes the paddle to stick.

When they work well at lower RPM's but when you accelerate they slow down, that is normal. The sudden drop in manifold vacuum when the throttle plate is opened suddenly causes that.

[jnissen]

Have you rebuilt the vac wiper motors with new seals? Even when working perfectly one of the complaints is that the wipers are slow! If your looking to keep it all original then every part of the system need to be inspected and tested for leaks.

BTW - Even electric wipers struggle on dry wind shields. Try misting the glass and see if this helps when testing. My electric conversion still spins the blades but I can tell it's working a lot harder on a dry windshield. Only had it out in the rain a couple of times since we rebuilt it but in those cases the wipers worked but were nothing to get excited over. The flat blades are very temperamental and require some futzing to make sure they are clean enough to wipe the glass properly. Most of the time you get about 50-70% of the blade only working and parts will not be properly touching. That is with new soft blades! We reverted to using RainX as a backup in case we really need to rely upon them.