Hi Fern and Group,Not trying to get any heated discussions going here, but consider the consequences of a power window relay welding itself together and the motor continuing to run until something broke, burned up or the fuse blew. Better hope for the fuse, but to handle the normal motor current, the fuse should be a slow blow or a circuit breaker used, which means no instant relief. Just try to find a part for those little gear boxes, I have and its not easy.
Its not the duty cycle that concerns me with the small relays. In my mind, the contacts inside these miniature relays must be...uh... miniature, there just isn't room in there for large contacts nor for a large open gap. If a contact starts to pit or to transfer some material to the other side, it could eventually not be able to open enough to break the circuit or might even weld together. If that happened, the motor would continue to run.
I have a hunch that these little motors draw a large amount of current to start and may generate a good little arc when being stopped as well. It's been almost 40 years since my last DC motors class, but as I recall, without an external starting series resistance, the starting current of a DC motor could be 10-12 times running current, much more than an AC induction motor. Someone said the rated current is about 12-14 amps, that means the relay has to potentially carry 100 amps or more for a split second. The contacts inside the OEM power window switches are just about the same size as the Mopar starting relay contacts, if memory serves, which would presumably make them larger than the miniature relay contacts. The factory would have put smaller contacts in these switches and relays if they thought they could get away with it.
Maybe I will get one or two of these relays and do some experimenting. First thing is to crack one open and see what it actually is made of, maybe they down sized everything but the contacts. I have a couple of 70's vintage power window motors I can play with if I can figure how to put a load on them.
Bill Huff At 11/30/200611:25 PM, Fern Rivard wrote:
There shouldn't be any problems in using what we used to call the
"auxiliary lights" relays or "horn relays" we have been used for years
to trigger the horn in vehicles equipped with radio telephones and two
way radios when a call was received. We have found that those compact
relays worked just as well as the larger normal horn relays but these
had the advantage of being very compact and very inexpensive to replace.
Also, remember that the duty cycle of operating power windows is not
for such a long duration and not repeated that often.
Just my 2 cents worth from Fern in cold wintery Cranbrook SE British
Columbia
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