Wiper motor relay

[manoa matt]

I've been trying to diagnose a constantly blowing fuse for the windshield wiper in a friends car. The wiper rack is free and moves without resistance. I took the motor apart, cleaned and re-lubed it. I have not yet cleaned all the electrical terminals within the circuit, that should help some. I also plan on replacing the wiper blades and applying rain-ex to the windshield.

The fuse will blow after the wipers make about 5-10 sweeps.

From searching the forum archives I know that Ventura Ace and Mdrbruchette were trying to work out a way to relay the motor similar to the headlight relay trick. Also SoCal Mark said he came up with a way to do it.

Anybody have any insight as to where to add the relay? BTW its a 1979.

[racydave]

According to the schematic, fuse 2 in the fuse box powers the wiper switch and the heater fan thru two brown wires. Decide which one powers the wiper, its the one that you want to power with the relay. The lt\blu wire from top of fuse 2 is from the ign sw, to be shared with the relay as input. A Bosch relay would be terminals, 30 is fused power from source, 86 is input or ignition, 87 is output going to feed switch, and 85 is to ground. I do not see any other way to do it. You also have two grounds, one for switch is in ground pod 3, and the motor is in g2.

[manoa matt]

Dave, thanks for the input. Hop over to Mirifiori.com, Tech questions. I posted there too and Greg Smith (headlight relay guy) gave me a schematic for a wiper motor relay install in an X1/9. See if my response makes sense in regards to his diagram.

[majicwrench]

Putting a relay in system is not going to solve the problem, the problem is that something in the system is drawing too much amperage.
If you have a situation, like the headlight issue, where you cannot get enough current to whatever it is you are trying to power, then a relay would help correct that.
Good luck,
Keith

[manoa matt]

Ok, so the motor was taken apart, cleaned and re-lubed. The wiper rack is free and moves nice. All grounds at switch and motor are new and good. Rain-Exed the windshield. Brown wire surgery helped across the board, and improved the speed, but the fuse still blows. There is no intermittent function.

I have a spare intermittent relay that I'll try. How do I test the amp draw on the motor?

If it still blows after installing the spare intemittent relay, Installing a relay or a new motor is the only fix I see. Any thoughts?

[mbouse]

i just realized that i had this same issue, blowing the wiper motor fuse... for no explainable reason. took for ever for me to figure out why changing a speedo cable caused issues with the wiper motor circuit. you see, i profess in the "go back to the last thing you did" theory... and the speedo cable was the last thing i did before i blew a fuse.

turns out, that when you drop the steering column to gain access to the back of the gauge panel, you run the risk of pinching a totally unrelated wire between the steering column and the frame it attaches to ... which might be a switched and fused hot wire for the wiper cirucuit

never under estimate Luigi and his magical movement of wiring.

[manoa matt]

Well, the column has been dropped at some point, as the small tabs are bent. However being that it is not my car, I don't know all the wiring history. I do know the three previous owners of the car, which is two more than I know for my own car.

The current owner actualy cares that the wipers work, I'll have to contact the next PO to see if they ever worked for him.

Sunday I had three Fiats in the driveway. My orange 78, my buddie's red 79 and Boogiedude came over with his yellow 78. I should have taken a picture.

[racydave]

Matt, according to the schematis, that fuse also feeds the blower circut. I use a amp meter with inductive pick for checking amp draw. You might want to disconnect the wiper motor and see if it still blows fuses. Also sounds like the intermittant switch, or wires could be at fault? With an ohm meter you could see if the wires are grounded to the frame with the connectors unpluged, or do the same with a ( simple )test light hooked to power.

[majicwrench]

TO test amp draw on motor you will need some sort of amp meter. A lot of the nicer mulitmeters have an amp function, many only up to ten amps. Inductive amp meters are nice too, but are not as good for measuring small amp draws.
Napa makes a nice little (cheap, $39 I think) unit called a fuse buddy, PN 7823308 which is basicly a bitty digital amp meter, designed for spade fuses. I have made all sorts of adapters for mine so it can be used just about anywhere.
I would recommend testing amp draw right at the motor, you already know there is too much amp draw at the fuse.
Keith