Relay question

Just how often can these cycle and still have a decent lifespan?

The wiper motor in the falcon crapped out on me. It is of course the two speed motor that is nla. I can order a new motor, switch and harness from a vintage ford supplier but am loathe to spend that kind of cash.

I found a 90's fox mustang motor laying around and with a 555 timer circuit and a few relays I have it functioning on the bench as an infinitely variable intermittent wiper with a single knob control that is pretty cool, but when it is running constantly the relays are switching a few times a second.

If this is within their range of operation I am inclined to let it be but if they will only last a few weeks I will have to do something different.

Thoughts?

A full size relay like that will probably have a short lifespan if its cycling constantly, I'd think.

I may be wrong, but if you go with a relay with a higher current rating that what you need, that should prolong the life of the relay (because of heavier duty contacts).

As a guess a properly selected relay should be able to cycle into the millions before giving up the ghost.

Here is some light reading for you:

http://bowery.com/maserati/home/files/bosch%20relays.pdf

They are cheap. I'd try it and see what happens. I'm betting it will hold up for a good while.

I'd be concerned with noise too, those things can be noisy when in constant use. I wouldn't want it inside the car

There's a number of solid state relays out there, like this one, which would probably be viable; http://www.amazon.com/HELLA-H41773001-Solid-State-Ceramic/dp/B000VU5FPE/ref=sr_1_1?ie=UTF8&qid=1441565266&sr=8-1&keywords=hella+solid+state+relay&pebp=1441565274448&perid=04EVMFBQ0V16FBWH1T9R

(grain of salt with that one, I spent about 20 seconds searching for a Hella branded SS relay, so you'll want to do a little homework before ordering)

Here's some reading about plus and minus's of these relays vs. traditional; http://electronicdesign.com/components/electromechanical-relays-versus-solid-state-each-has-its-place

I'd use a power transistor or solid state relay (which is just a power transistor in a box). By my math you're looking at maybe 100 hours of operation before failure with a mech relay.

Bosch makes a metal bodied version of that relay that is pretty stout. Look in 80s-90s Euro car fuse boxes at the junk yard.

What kills relays isn't generally the current over time but the number of cycles. Every disconnect erodes the contacts just a bit.

Look at how long fuel pump relays last (just about forever) versus ignition points (3-5,000mi). And points have lower voltage, lower current, and a much larger contact area.

I'd look into a solid state relay. I know they exist, since I've installed them, but I don't know where to get 'em offhand.

first 2 that came up when I googled "solid state relay"

http://www.cel.com/product.do?command=viewSelector&group=2&gclid=Cj0KEQjwyK-vBRCp4cymxermx-EBEiQATOQgh3bkYKrWdYxHi88-9ju9fXWmCZJWr3fQTwPfESr9PgkaAgkg8P8HAQ

http://info.opto22.com/opto-22-ssrs?utm_campaign=SSR%20-%20Google%20AdWords&utm_content=SSR%20GAWLP&utm_medium=search%20network%20text%20ad&utm_source=ppc&gclid=Cj0KEQjwyK-vBRCp4cymxermx-EBEiQATOQgh0Ce579Zn37quQTt4zF1sD0ipJGCO-oAgJ7HS9jf5p8aAhbh8P8HAQ

I wouldn't worry about it. Most of the time here in the misty NW you will have them on slow anyway, so maybe 1 cycle every 2-3 seconds.

In reply to bgkast:

You've actually got a really good point.

My wipers are on intermittent 95% of the time.

http://www.wolstentech.com/products/timedelayrelay/timedelayrelay.php

I was thinking transistor too, whats your amp draw?