Help - Wipers won't turn off!

Ever hear of this problem? After using my wipers in the rain, I tried turning them off. They stopped for a few seconds and started back on. When I try to switch from delayed wiper to fast speed - no difference in speed. Can't figure out what is the problem and why I cannot turn them off. I have a 1999 C2 996. Any suggestions?

Do you have a rain sensor?

No - mine has no rain sensor.

control unit is probably no good

Thanks for your input, guys. For some reason the problem has gone away. Hopefully forever!

Very old discussion here but want to update it so anyone having the issue of non stopping wipers knows how to fix it. Also causes the rear window defroster light to show. What happens is the car gets wet, usually out in the rain or was washed. I have not fixed why the water gets in, but it does, and gets the wiper relay wet on the fuse board. The fuse board is inside the car, left side of driver footwell. Picture of wiper relay below. (Also gets rear window defrost relay wet causing light to stay on). Pull the relay and then use a dry rag and a Q tip to dry out the contacts inside the fuse box. A blow dryer helps but be careful not to get it too hot, I used the "cool" setting. Also helps to run the car heater with fan on high, blowing down to the foot area. You can dry out the relay by shaking the water out and using a blow dryer, or replace it with another relay until the wet one dries (leave outside in the sun or let it sit for a few days in front of a garage fan etc.). Typically if the car sits in a warm dry place for several days the problem will go away.

One place to check are the "wells" and drains on either side of the battery compartment. If the drains are clogged there will be a lot of water in there. Remove battery cover and then the two plastic covers on either side of the battery. Check for sitting water and clear out the drains.

There r drains that run doen the a-pillar for the sunroof and in the battery area of the cowl. Do a sesrch for the locations and get them cleaned out. eventually this wil get worse and your imobilizer will get wet and cost some $

Quotes source post: 17714222

Thanks. After several times leaving my 996 in the rain this has happened, and have checked the area under the battery on both sides - the drains are clear and no water sitting. I should had mentioned its a cabriolet, so no pillar drains. Have read many posts on this and most say it happens after rain or wash, so my untested theory is the water comes in from windshield down to the fuse box area. Or possible from the battery area then down into the fuse box area. I am able to confirm no water is coming from the top or doors. There is a small trickle stream of water coming from above the fuse box (left side of driver footwell). Since this seems to be a common issue, if anyone figures out how to stop the water from getting in, would be very helpful. I'll update this if I figure it out, will be pulling things apart between the front trunk and the dashboard to see if I can locate the source.

[Image-only post; no author-written text. Original image references:] https://cimg3.ibsrv.net/gimg/rennlist.com-vbulletin/941x713/cab_drains_c8831845601fc2c92cef2dc1e95e61805e204db8.jpg

This is an update to my post on 10-8-21 above. Below is how to stop the wipers from constantly running - immediately and easily. Also how to fix the problem. This will also fix the issue of the rear defroster light staying on. The problem on my 996 and likely many others is that water was getting in under the dash, onto the relay board (inside of car under dash, far left side of firewall). In my case I left the car out in the rain, but it has happened before after a car wash. Then after a week of the car sitting in a dry place the problem went away. Unfortunately this has happened a few times. Glad now to find the source and stop future havoc on the relay board and electrical system. 1). If wipers won't stop with the switch and you need to stop them quickly, turn off the car then pull the wiper relay from the board. After you pull the relay start car and wipers will work (no intermittent) and you can now stop them. To locate the relay, it is on a board with other relays, located under the driver side dash on the far left side of the firewall. The wiper relay is the only one that is larger than the others and it is blue. See pics below. 2) To dry out the relay, with a screwdriver pry the plastic cover off until the relay circuit board comes out of the housing. See pics below. Dry out inside of housing with a paper towel. I used a fan to blow dry inside of relay circuit board etc. With car off, I also pulled all the other relays and dried them, then with the battery disconnected , I used a paper towel over a screwdriver head to poke in the holes where the relays go, and dry them. Then used a blow dryer on 'cool' to dry out the relay board. Also helped to run a fan under the dash facing the relay board over night. 3) After pulling the inside of relay out, if there is rust on the flat side of the circuit board side of the relay, it can be cleaned off. I used a toothbrush with a little bit of orange cleaner, see pics. (zep degreaser is a staple in my garage). Then dry with a paper towel. Do not get the side of the board wet that has resistors and components on it. Then blow dry both sides on cool and make sure its dry, then put it back inside the relay housing, should pop back in if you have inserted it the same way it came out. 4) I found the water to be getting in on the far left of the drivers side directly under the wiper arm - there is a removable plate (inside of trunk) that allows access to under the dash board - see pics below. The water was getting in by collecting around the base/seal of this access plate. The factory seal is not keeping water out. Also on my 996 a previous owner had cut holes into the plate for cables to be be run for a stereo amplifier. See pics. Remove the plate - three screws (get better access by removing the windshield cleaner access tube - pull left). My apology the pictures stop there, it was beer time. However to stop water from coming in, I put a bead of RTV silicone around where the seal connects to the plastic cover plate, put it together and clamped it, and let dry. Once dry the plate and seal are one solid piece. Then screwed the plate back into the car, and afterward put a bead of RTV around the base of the seal where it contacts to the car. Ran another bead around it with my finger to make sure it was completely sealed and let it dry. Later I tested it by using a garden hose to simulate rain, let it rain for about 10 minutes, and checked under the dash. It was dry, no water. Used toilet paper underneath to confirm no water was getting in.