Mechanics

WINDSHIELD WIPER PROBLEM

1996 Chrysler Town and Country

Electrical problem
1996 Chrysler Town and Country 4 cyl Front Wheel Drive Automatic

Hi! I picked up a 96 T & C with 178K that has been sitting dormant for a while. It wouldn't start and I had to put a fuel pump in it and it also had a leak at the transmission pan, so changed the transmission filter, oil & gasket. So far, everything has worked out great, but I am having a problem with the wipers. They didn't work, so I checked the green 30 amp fuse and tried exchanging relays in the power distribution center. They do work when you use the washer, so the wiper motor is okay. Also for a while, when I pushed the washer, the wipers would run and would change speed according to how I had the wiper switch set, faster or slower, but they would continue to run even when I shut the wiper switch off and also when I shut the key off. I had to keep hitting the washer switch to finally stop the wipers. I tried exchanging the relays again and now the wipers only move when I use the washer, but do not continue to run. I disconnected the plug on the firewall and found constant 12 volts in one wire and a much lower voltage in another, but I am still clueless. The fact that they continued to run after shutting off the ignition switch kind of makes me suspect it is a relay problem, but I'm not sure how to proceed. Any ideas?
Thanks
Evan
Avatar
Drern
March 21, 2010.



This is actually a real common problem since the engineers got the insane idea to hang an unnecessary computer onto every imaginable system. The problem is caused by the Body Computer. It is tucked up against the firewall in front of the brake pedal. Three screws hold it in, then it is pulled down to unplug it from the fuse box.

Caradiodoc

Caradiodoc
Mar 23, 2010.
Thanks so much for your reply. So, am I to assume that the body computer needs to be replaced and is there a way for me to determione it is definitely the problem?
Thanks again : -)
Evan

Tiny
Drern
Mar 23, 2010.
The only way to know for sure in this case it to replace it. Normally I hate throwing parts at a problem in hopes one will stick and fix it, but because of the design, nothing can easily be tested. On the '95 and older vans, you could backprobe the wires in the connector to determine if the computer was receiving an incorrect command from the multifunction, (turn signal) switch, but on the '96 and newer vans, the connector is way at the top of the module where it is not accessible. You might be able to access the wires at the signal switch, but the computer has been such a common problem, I sent you there first.

Had a community member bring one to my school many years ago with the same symptoms. He figured out a way to run a pair of wires to a toggle switch that he mounted on the steering column. That gave him one steady speed but no delay function. Everything else controlled by the Body Computer worked fine so he was satisfied.

There IS a problem that often developed with the multifunction switch. It is called " phantom wipe". This is where the wipers will make one swipe at who-knows-when, then stop. The Body Computer determines the switch setting you chose by reading the value of various resistors the switch selects. One resistor is off in value just a little, but enough to confuse the computer. I autopsied a switch once to see if I could modify it but it wasn't practical. The replacement switch has three part numbers on it. One is for Chrysler, one is for Toyota, but don't know who the third one is for.

Caradiodoc

Caradiodoc
Mar 23, 2010.
Thank you once again for your valuable insights. The onl; y thing is I " looked around": on the web and it appears that it will cost roughly 350 - 450 to have my BCM rebuilt and that is a lot considering what I have invested in the car so faR ($600). So considering that, isn't the other probable cause the actual wiper switch? If so, can't I test that first to rule it out, thereby increasing the chances of it being the expensive BCM?
Thanks again
Evan

Tiny
Drern
Mar 23, 2010.
There are a bunch of these in the salvage yards, but look for one that you can return, say in 30 days, if it has problems. I'll be heading to some " Pull-A-Part" yards in Indiana and Kentucky soon. Modules there are less than 50 bucks. I can hunt for one there, but I don't have any way to test them.

You can't make any voltage tests at the module because the connector is up on top. The module unplugs when you pull it down. What you can do is measure on the other end of the wires at the signal switch. This is a really complicated circuit, but there are some things you can try or verify.

First, you need to be able to make the wiper motor run. If you can still do that by pressing the washer button, fine. If not, you can insert a jumper wire in terminal 85 of the " Wiper On" relay under the hood, put the relay back in, and ground that wire. The motor should run on slow speed. When you put the wiper switch in the high position, the motor should speed up. That proves the " High / Low" relay, " Wiper On" relay, and the " high" section of the switch are working. If the motor runs when you press the washer button, it proves the Body Computer's switching circuit is working.

The only thing left is the delay speed sensing circuit. There are two wires between the switch and the computer that you can access by removing the switch. I can't tell from the diagram which wire supplies the voltage and which one is the sensing wire, but what you're looking for is a varying voltage on one of them. One is the black wire with a white stripe. The other is a dark green wire with a red stripe. When you measure the voltages, I believe one wire should have 12 volts, (possibly 5.0 volts). The other wire should have a different voltage depending on the switch setting. In the " Off" position, both wires will have the same voltage. The voltage on the black / white wire will be the same on the " high" and " low" setting.

Anytime the voltages on the two wires are different, the computer detects that as a delay or " on" position. If you find 0 volts on both wires, it is possible one wire is broken, or the voltage is not being supplied by the computer. If you find the same voltage on both wires regardless of switch position, there could still be one broken wire, but more than likely the break is in the circuitry inside the computer.

The last circuit should not be involved, but it is the " park" circuit that keeps the motor running until it gets to the " park" position when the control switch is turned off. That is the dark green / white wire in the motor connector. There should be some voltage on that wire when the wipers are parked. It should have 0 volts whenever the wipers are moved out of the park position.

Caradiodoc

Caradiodoc
Mar 23, 2010.
Thank you so much once again, for your knowledge, time & expertise! :-)
If I can ever help you witrh a Chiropractic question, please let me know!
e-mail: drern@optonline.net
Website: http://www.DrNeilsonChiropractor.com

Tiny
Drern
Mar 24, 2010.