MOloghauler Posted February 28, 2019 Share Posted February 28, 2019 This started about a month ago, my wipers got to where they would run for a bit then shut off for a few beats and then kick back on. Then they quit completely. Being impatient as I am I went for the quick fix and swapped the wiper motor for a new one. Same thing, nothing. They would work on high every now and then but that was it. So I replaced the switch, still the same thing. Only work on high when they want to. So I got to digging through the wires and found one red wire that went the opposite direction from all the other wires, and followed it to a relay mounted behind the fuse box. That HAD to be the problem... replaced the relay, checked all the other wires, and you guessed it.. still nothing. They work on high only. Am I missing something? The wiring seems very simple, the switch and motor are both Mack parts, but I’m at my wits end with these wipers! Anybody have any ideas? Quote Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/ Share on other sites More sharing options...
41chevy Posted February 28, 2019 Share Posted February 28, 2019 (edited) Check the ground or better yet run a new ground for the wiper motor. Edited March 5, 2019 by 41chevy Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/#findComment-416829 Share on other sites More sharing options...
JoeH Posted March 2, 2019 Share Posted March 2, 2019 My 95 RD688 you have to hold the switch just right to get it to work. We have never replaced the switch, but maybe it's a crappo switch design? Quote Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/#findComment-417008 Share on other sites More sharing options...
41chevy Posted March 4, 2019 Share Posted March 4, 2019 On 3/2/2019 at 8:59 AM, JoeH said: My 95 RD688 you have to hold the switch just right to get it to work. We have never replaced the switch, but maybe it's a crappo switch design? If you need to hold the switch "just right" to make the wipers work, that points to a worn switch. The contacts to loss their tension with age. 24 years is a good life span IMO. Paul Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/#findComment-417154 Share on other sites More sharing options...
MOloghauler Posted March 5, 2019 Author Share Posted March 5, 2019 Mine was that way for awhile, that’s why I went ahead with the new switch. I’ve checked grounds, ran new grounds, checked all other wires and still nothing. I’m thinking about just wiring in a 3 way toggle switch and only having high and low. Anything would be better than what I’ve got at this point Quote Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/#findComment-417288 Share on other sites More sharing options...
41chevy Posted March 5, 2019 Share Posted March 5, 2019 51 minutes ago, MOloghauler said: Mine was that way for awhile, that’s why I went ahead with the new switch. I’ve checked grounds, ran new grounds, checked all other wires and still nothing. I’m thinking about just wiring in a 3 way toggle switch and only having high and low. Anything would be better than what I’ve got at this point The wiper motor should have a ground wire in the harness but some also ground through the wiper mounting bolts check that first. Also use your multimeter to bridge between the low speed terminals on the switch and the wiper motor; with the switch moved to “Low” you should get at least a 10-volt reading. Repeat the exercise with the intermediate speed. If both circuits are not reading close the problem is in the harness most likely. Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/#findComment-417298 Share on other sites More sharing options...
MOloghauler Posted March 5, 2019 Author Share Posted March 5, 2019 I will check that, I’m having such a hard time finding electrical info on this truck. Seems like everything on it has been re-wired by 5 different people and every one of them got it wrong 🤦♂️ Thank you for the info! Quote Link to comment https://www.bigmacktrucks.com/topic/55875-1993-rd688-windshield-wipers/#findComment-417309 Share on other sites More sharing options...
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