740 wipers only work on one speed and won't park Topic is solved

Ursula · Post by **Ursula** » 18 Aug 2004, 06:33

i recently acquired a 88 740Turbo and it's a fun car so far EXCEPT that when I use the front windshield wipers they only work on the fastest speed....I even swapped out the front wiper relay with three I had pulled from junkers to see if that would help but it didn't change anything....I guess if the wipers work at all it's not a relay problem? also, when I turn the wipers off they won't park flat, I have to time it just so...anybody have any clue what else I might check....thanks so much.

TAFinley · Post by **TAFinley** » 18 Aug 2004, 09:08

I had a similar problem on my '85 245GL. The wiper motor is the same as yours.

My wipers started parking in the fully up position. I found that the nut that holds the main wiper arm to the wiper motor shaft had loosened. and the arm had slipped on the shaft.

To fix this, you need to disconnect the main arm from the wiper motor shaft and cycle the wiper motor a few times. It should start to park itself normally. Once it does park normally, you can reattach the main wiper arm. It takes a bit of manipulation to get the main wiper arm into the correct position.

I don't know why your wipers are running in high-speed only.

Guest · Post by **Guest** » 18 Aug 2004, 12:13

TAFinley wrote:I had a similar problem on my '85 245GL. The wiper motor is the same as yours.

My wipers started parking in the fully up position.

not quite the same problem I have. Mine park wherever they happen to be when I move the stick to the OFF position, could be 12 o'clock, 1 o'clock, 2, or 3 (flat). I've started to time it so that they park flat (after one or two tries that is) but it's an annoyance.

LaRy · Post by **LaRy** » 18 Aug 2004, 13:08

My guess is that you have something wrong with the windshield motor low speed function. If low speed does not work, the return to flat position does not work either, because the return function is using the low speed of the motor. A motor like this has three brushes, one is common and the other have different position, they have some degrees between each others. Depending on what brush that is connected, the speed will be low or high. I would take out the motor and check the motor brushes that the are good and the springforce is good and that the brushes are not stocked. It is rather complicated to take out the windscreen motor, so hopefully you have a good manual. The motor will be found under the air intake plate, so it will be removed from the outside of the car. You will also find some small switches making it run and finding flat position, check that hey are clean and not burned. It could actually be just a simple problem like a bad connnection to the cable.

Guest · Post by **Guest** » 18 Aug 2004, 13:20

Thanks LaRy! I'll get out my ratchet set tonite (if I can dodge the mosquitos) and take a look at it. I have a Haynes manual, but this will be my first time messing with the wiper motor. Don't be surprised if you see another message from me screaming HELP!!!

LaRy wrote:I would take out the motor and check the motor brushes that the are good and the springforce is good and that the brushes are not stocked. It is rather complicated to take out the windscreen motor, so hopefully you have a good manual. The motor will be found under the air intake plate, so it will be removed from the outside of the car. You will also find some small switches making it run and finding flat position, check that hey are clean and not burned. It could actually be just a simple problem like a bad connnection to the cable.

TAFinley · Post by **TAFinley** » 18 Aug 2004, 14:46

LaRy is correct about the functioning of the wiper motor. There is a contact that travels over a plastic disk that has a depression in it. When you flip the wiper switch off, the contact maintains power from the low speed circuit to keep the blades moving until they reach the parked position, which is the position they should be in when the contact drops into the depression on the plastic disk, thus breaking the contact and stopping the motor.

I would advise you not to remove the motor unless you absolutely have to. The motor is held in with jus three bolts and looks simple to remove, but the moisture seal is accomplished by surrounding the shaft housing with a couple of ounces of some sticky black goo like roofing cement. To get the motor resealed, you'll have to buy some similar black goo and apply it. In fact, the last time I pulled one of these motors out, I got a tube of non-hardening roofing cement to reseal it.

If you remove the metal disk over the gear housing, being careful to keep the plastic gasket sheet intact, you can clearly see and access the three electrical contacts. The one on top is the one that keeps the motor going after you've switched off the wipers.

The electrical cable plugged in to the motor tends to get rather brittle with age. Be careful if you unplug this cable to perform diagnosis of whether power is being supplied correctly; the plastic plug housing tends to break easily.

Ursula · Post by **Ursula** » 19 Aug 2004, 06:00

Thanks for your thoughtful response. It rained like all dickens last evening so i didn't get to work on it. You think I might be better off just getting a junkyard motor and testing itand replacing the whole motor (black goo-alert notwithstanding)? Also, if I have them test it at the junkyard (the motor) how can I determine if the two-step process is working? I'm pretty good with a wrench but electrical circuitry and me never get along very well (I keep plenty of fuses and relays in my emergency toolkit ... don't ask me why).

TAFinley wrote:The electrical cable plugged in to the motor tends to get rather brittle with age. Be careful if you unplug this cable to perform diagnosis of whether power is being supplied correctly; the plastic plug housing tends to break easily.

TAFinley · Post by **TAFinley** » 20 Aug 2004, 07:24

Ursula:

I found a wiring diagram for the motor. I've included the wire colors from the diagram I found. It's from an '84 245. The wire colors may have changed, but the motor is the same so the positions of the wires haven't. Here's how the pins work.

Looking directly at the connector on the motor, the bottom right pin (yellow wire) supplies power to the stop circuit, the contact that falls into the little recess on the plastic disk (this is always powered up). The bottom left pin (brown wire) supplies power for low speed operation. The top right pin (green wire) supplies power for high speed operation. The top left pin (black and white striped wire) is the neutral. If you have two pins in the center, they do nothing.

To field-test the motor, you need to get a 12-volt source on to the stop circuit, then connect a 12-volt source to the low speed pin (the motor should run at low speed, then stop when the stop circuit contact falls into the recess on the plastic disk), disconnect, and then connect a 12-volt source to the high speed pin (the motor should run at high speed, then stop when the stop circuit contact falls into the recess on the plastic disk). Of course, you need a connection to the neutral pin as well.

I wouldn't be afraid of the black goo; it's just really messy and if the new goo is not applied correctly, you'll have water leakage into the passenger compartment. I'm sure your Volvo dealer will sell you a tube of black goo, but it will probably be more than several times the cost of a tube of non-hardening roof cement (mine cost me less than $2 US).

Good luck with your motor.