Asked in Car Fuses and WiringChevy S-10Windshields and WipersFord Explorer Limited
Why does the windshield wipers on your 1988 S10 blazer work sometimes and not others. Is there a fuse or plug-in that might be replaced before you invest in a wiper motor?
August 30, 2007 7:46PM
As I am a Ford man, but basic auto electrical systems are similar, if not the same, this answer will be "generic" in nature. The troubleshooting process for this problem is pretty complicated for one not experienced in auto electronics, and suggests the need for the services of an automotive electrical systems technician. However if you want to try to fix this yourself, then the following troubleshooting protocol is provided, BUT with one caveat. That is that messing around with auto electrical systems by unqualified personnel CAN RESULT in severe damage to the vehicle, fire, and possible severe injury to people. Unless you are qualified, don't try to fix this yourself. Do not invest in a wiper motor Yet. Although it is possible that a wiper motor could become defective, I would bet a dollar to a dime that your motor is not the cause of this problem, as this occurance is very infrequent. So, replacement of the motor should be the very last option to try. You can first test the motor by disconnecting the motor from the circuit by disconnecting the motor wiring harness at the connector closest to the motor [this is usually an inline connector within a few inches of the motor]. Then carefully, using jumper wires, securely connect one of the wires to one of the motor connector contacts and securely to the negative terminal of the battery. Then securely connect the second jumper to the other motor connector terminal contact. Then, only touch the other end of that wire to the positive terminal of the battery. If the motor is "good," then it should begin to run, causing the wiper blades to operate. If the motor does not operate, the next step I would suggest is to securely connect a volt-ohm meter to the motor connector contacts, with the meter set to read resistance [Ohms] on the lowest setting [usually, one (1)]. This is a test for "continuity" [circuit closed or open] of the circuit from the connector to the motor brushes, through the windings, and back to the other connector contact. If the battery "run test" fails, and this continuity test indicates that the circuit is open, then the motor is probably defective and requires replacement. First, almost all windshield wiper systems have an intermitent mode of operation in which the position of the control switch will cause delays [some very long] between wiper strokes. On the assumption that you are aware of this, and that you have not inadvertantly placed the control in the delay mode position, the only other reason for delayed, intermitent, or a total failure to operate would be an open circuit caused by a loose or corroded contact somewhere in the circuit supplying current to, or the ground from, the wiper motor. This could be inside a connector anywhere within the entire circuit, including switches or ground connections. It could also be a defective component on the circuit board for the delay function. It could be anywhere within the circuit. The diagnostic key here is that the circuit continuity problem is intermitent, and therefore is subject to change as a result of the contact changing from closed to open and back. This could be caused by corrosion at the contact point, a loose or damaged connector or connection, a cut or pinched wire that only makes contact part of the time. To correct this problem, the defect must be eliminated. In order to do that you have to find the defect. Usually, finding the defect is the hard part of the exercise, and the repair itself is usually relatively easy. So, how do you troubleshoot the circuit in order to find the mysterious, intermitent defect. First, you must visually examine all of the wiring and devices, from the battery, going to the control switch [inclluding all connectors], any relays in between, the control switch, wiring to the motor, and the motor ground. Look for loose connectors, loose terminal set screws, evidence of overheating [dark discoloration of wire insulation or plastic connectors], melted plastic connectors or insulation, the same for the control switch itself, etc.]. In effect you are looking for anything which does not look "normal" as compared to the rest of the wiring in the vehicle. During this inspection process, carefully disconnect all connectors to allow inspection of the contact pins and sockets for evidence of overheating, and especially corrosion. After inspection, they must be securely reconnected. If any abnormalities are found, correct them as they are found, and then test the wiper system to see if that corrects the problem. If not, then continue the troubleshooting protocol all the way to the motor ground connection. As it has been years since I did this kind of work, I am hopeful that I have not forgotten something in this process. However, IF you have some experience in auto electrics, and with what info is here, you should be able to locate and correct your problem. Good luck.j3h.