There’s a 1992 Mazda MX-3 that has windows that no longer operate properly. The owner (not me) has previously taken the car to her mechanic who tried to fix them and got them working again for a while, but said that the only permanent fix would probably be to replace the doors. The sticking point is that the car has manual windows and the potential replacements found online are power. Is it possible to install the doors with power windows and get them to work? I can see it being as simple as hooking up unused wires from the wiring harness, or as difficult as the wires/connections not being present in the car. Would this work in general and can anyone give a definitive answer about the MX-3?
I can’t speak to the wiring harness, but in principal, anything’s possible, even if the existing harness doesn’t support the power windows. Essentially, you have a switch and motor. All they need is power. I’d try to get a schematic to ensure that all of the control is strictly hard wired in the door, rather than processed through a computer. Given that it’s a 1992 Mazda, I’d certainly not guess that there’s anything more sophisticated than hard wiring.
Okay, that’s not helpful, so for practicality: look at the wiring diagram (Haynes books, maybe?). There’s probably only power that’s required. In all likelihood, the switch powers the motor directly. The clutch/overload/whatever is integral to the motor. If the existing harness doesn’t have the 12VDC, you can run some fresh wires from the fuse block, and there’s probably a blank space for the power windows. If it’s not blank or multi-use, just draw off of that fuse.
I’m really surprised at the prognosis of needing to replace the doors. The only two scenarios that come to mind that make any sense are that the doors are badly rusted inside or badly dented. Either condition would have to be severe enough to where the mounting for the window tracks and/or regulators was really messed up. I’ve never seen rust that bad in that area, and I’m finding it hard to believe there could be denting that bad without other bigger problems. I would strongly recommend a second opinion here - it just doesn’t sound right to me.
Moving beyond that, if the doors are going to be replaced, yes it would be possible to get the power windows to work. It may or may not be easy:
~ Power supply goes through a main fuse, then the ignition switch, then a power window fuse, then to the master switch in the driver’s door. Best case, it just needs to have the window fuse installed. Not so good cases: the wiring harness in the car doesn’t have the portion from the ignition switch; the window fuse slot doesn’t have terminals; the harness in the car doesn’t have the portion from the fuse box. Nevertheless, this can all be fabricated with wire and a fuse holder, so it’s not a huge problem.
~ Five wires for this are in the driver’s door harness: power, ground, and three that go to the other side of the car to the passenger door harness. Best case: the doors come with complete (all the way to the connector) harnesses attached AND the vehicle harness has the wiring - then you just plug the door connectors in on each side and you’re ready to go. Not so good cases: the replacements are used and the door harnesses have been cut; the vehicle harness doesn’t have the portion that goes from left side to right side. Fabricating here means harness construction and (with door wires cut) lots of splicing.
~ Definitive answer? I would have to inspect the vehicle and compare it to a wiring diagram to tell what was there and what was not. Probably the easiest way to find out is to call a Mazda dealer and ask if the the same wiring harness is used for cars with manual or power windows. If so, everything should be there except the fuse, and cut door wires would be the only real concern. If not, looks like a bunch of work. To avoid disaster, make sure the person doing said work really understands automotive electrics and has the proper repair info.
You didn’t ask, but be aware - on some cars, replacing doors is a pain. The challenges can lie in accessing the hinge bolts and/or aligning the door.
You wouldn’t believe the amount of money we spend to ensure that doors are properly aligned. Granting, we’re hanging up to 70 jobs per hour, but it’s one of the tasks that requires the most precision without being able to use simple locators.
The way I’ve seen it done is to put the door as best as possible and then either pull hard the whole door upwards or push downwards. Sometimes this is the only way to have a good fit, especially when putting a second hand door on an old car.
Of course the customer must not be around. Ignorance is bliss
Get an opinion from a second mechanic.
This sounds fishy.
Your friend might be better off taking the car to a auto body repair shop that would be able to get her a better idea of what needs to be replaced. Unless the door actually has physical damage to it or severe wear or rust, she probably only needs new regulators for the windows. Any competent shop should be able to give her a few options. Changing a factory manual door to a power window door isn’t a simple matter of connecting wires. On a 16 year old vehicle, I would seriously doubt it being worth trying.
FTR, I’m not really mechanically inclined, but with a Haynes manual i was able to swap out a manual window regular in 45 minutes one afternoon in my mom’s driveway.
Also, don’t buy used; a junkyard regulator is probably getting ready to go just like your old one, unless it got pulled from a car with low miles.