My next hot rodding project was a result is driving in light rain a couple of weeks ago. I kind of wished I had intermittent wipers in the light rain. I conducted some research and found modules intended for boats that looked like it could add intermittent wipers to a car, truck or boat. Modules supported 12V or 24V, single or dual motor systems.
I looked into rain sensing wiper modules, and I did find a couple, but I decided those might be a bit too much for the rig.
I admit this is not for everyone, but I figured I would post my findings in case someone else has the itch for intermittent wipers and did not mind how I got them.
First let me state that if you want to not mangle up your wiring, this is not for you!
Don’t order the above. It will not stand up.
One morning, I got up before the Florida Inferno heated up in 90's and mocked up the wiring the module up. The metal tags going into the motor were well marked, with ones marked "L" (low speed), "H" (High speed), "P" (Park) and “B” which understand stands for 24V Positive. Tested with a VOM the outputs on each wire, and with all switch positions. Here are the results with the stock switch, mostly out of curiosity:
Please note that on the M998 schematic above, it shows only three wires plus a ground, but my harness from the original switch had 4 wires plus a ground. I believe wire #4 is the B lead.
Also please note that when the rotary switch is in High, the low lead has 33 volts present! I am not sure how that is even possible!
After you cut the wires between the motor and the switch, the controller will provide the necessary voltage and sensing.
After frustration with the first controller, I did a bunch more looking and I found this replacement:
Intermittent Marine wiper controller
Here is how to wire it to the M998 Wiper Motor:
Make sure you label both ends of all four wires then cut them with the power off and hook up all the leads before plugging the harness into the controller. Do NOT cut the ground wire to the motor housing, that is still needed.
What I like about this unit is that if you hook something up wrong, the module can be reset by disconnecting the harness in the back of the module for a minute and it comes back as factory reset. Seems to have robust electronic protections.
I had already bypassed the two sets of three contacts under the windshield that provide the +24V, Ground, and Washer +24V, as I have a helmet top and cannot easily remove it to gain access to replace the corroded contacts. So making up a new harness from the Wiper motor to the control module was not a big deal. I used a 4 pin quick disconnect harness I had laying around to be able to quickly disconnect this from the wiper motor if even necessary, like to remove the doghouse.
The controller has a standard marine rocker switch format to make mounting it in a pleasing manner.
For mounting the controller switch I had a few options. I have a rocker gang but there are no empties. It would be a great deal of work to redo the console I built with an expanded rocker gang mount.
I could mount the controller in the console elsewhere but I think it would have looked a bit goofy and I would have been limited in locations since the controller is deep and I have an AC evaporator inside there that limits the depth, or locations that have sufficient depth.
Instead, I thought I would try mounting the controller near the wiper motor in a rocker gang container box.
3 Rocker Switch Box
I removed the stock rotary switch completely and mounted the rocker switch/controller on the bracket.
I recommend this modification as it is fairly reasonably priced, and seems to work well. The modification can be reversed if needed.
I looked into rain sensing wiper modules, and I did find a couple, but I decided those might be a bit too much for the rig.
I admit this is not for everyone, but I figured I would post my findings in case someone else has the itch for intermittent wipers and did not mind how I got them.
First let me state that if you want to not mangle up your wiring, this is not for you!
- The stock Wiper/Washer rotary switch use cannot be kept.
- You have to cut the wires between the wiper/washer rotary switch to the motor itself. If you do not, the internal wiring in the switch will interfere with the module and you will blow fuses, assuming you have any.
- You have to rewire the washer motor as the old switch provides ground, while the modules provide +24V. Since I has installed a different pump previously this was not hard for me.
Don’t order the above. It will not stand up.
One morning, I got up before the Florida Inferno heated up in 90's and mocked up the wiring the module up. The metal tags going into the motor were well marked, with ones marked "L" (low speed), "H" (High speed), "P" (Park) and “B” which understand stands for 24V Positive. Tested with a VOM the outputs on each wire, and with all switch positions. Here are the results with the stock switch, mostly out of curiosity:
| M998 | Motor | Wiper | Leads | |
| Switch Position | (H)ight | (L)ow | (B) | (P)arked Signal |
| #1 | #2 | #3 | #4? | |
| Off | 0.01v | 0.01V | 24V | 24V |
| Low | 12V | 24V | 24V | 24V while running 0V when wiper in Parked position |
| High | 24V | 33V | 24V | 24V while running 0V when wiper in Parked position |
Please note that on the M998 schematic above, it shows only three wires plus a ground, but my harness from the original switch had 4 wires plus a ground. I believe wire #4 is the B lead.
Also please note that when the rotary switch is in High, the low lead has 33 volts present! I am not sure how that is even possible!
After you cut the wires between the motor and the switch, the controller will provide the necessary voltage and sensing.
After frustration with the first controller, I did a bunch more looking and I found this replacement:
Intermittent Marine wiper controller
Here is how to wire it to the M998 Wiper Motor:
| M998 | Motor | Harness | Lead | ||||
| Harness Cable Color | (H)igh | (L)ow | (B) | (P)ark | Washer | Ground | +24V Fused |
| White | Yellow | Green | Blue | Brown | Black | Red |
Make sure you label both ends of all four wires then cut them with the power off and hook up all the leads before plugging the harness into the controller. Do NOT cut the ground wire to the motor housing, that is still needed.
What I like about this unit is that if you hook something up wrong, the module can be reset by disconnecting the harness in the back of the module for a minute and it comes back as factory reset. Seems to have robust electronic protections.
I had already bypassed the two sets of three contacts under the windshield that provide the +24V, Ground, and Washer +24V, as I have a helmet top and cannot easily remove it to gain access to replace the corroded contacts. So making up a new harness from the Wiper motor to the control module was not a big deal. I used a 4 pin quick disconnect harness I had laying around to be able to quickly disconnect this from the wiper motor if even necessary, like to remove the doghouse.
The controller has a standard marine rocker switch format to make mounting it in a pleasing manner.
For mounting the controller switch I had a few options. I have a rocker gang but there are no empties. It would be a great deal of work to redo the console I built with an expanded rocker gang mount.
I could mount the controller in the console elsewhere but I think it would have looked a bit goofy and I would have been limited in locations since the controller is deep and I have an AC evaporator inside there that limits the depth, or locations that have sufficient depth.
Instead, I thought I would try mounting the controller near the wiper motor in a rocker gang container box.
3 Rocker Switch Box
I removed the stock rotary switch completely and mounted the rocker switch/controller on the bracket.
I recommend this modification as it is fairly reasonably priced, and seems to work well. The modification can be reversed if needed.