QuestionQUESTION: Hello Roland, I am asking for follow up help on a problem I have on my 2005 Chrysler town and country with more info. I hope you recall it. Wipers, blower, windows, radio will not work when first started. Problem has gotten progressively worse[ stays off longer]. I have replaced the TIPM module with no change. I have since noticed that if I start it and turn the key off to the [key on engine off] position everything works fine till I start it again. When it is running and nothing is working if I push and hold in the rear wiper/washer button radio will come on and off and windows will function slowly. It has been suggested to me that the BCM is the culprit. What are your thoughts? Again I really appreciate your time and effort.
ANSWER: Hi Rob,
I suspect the bcm is involved but whether it is faulty is another question. I do however notice that the ignition switch communicates to the body computer via two internal switches and an array of resistors rather than communicating to many circuits by a bunch of internal switches and many wires as in earlier days. The idea is the bcm measures the resistance which should vary depending upon whether the key is in the lock or not, and also which position the switch is sitting in. I don't know the logic (what resistance value means what to do) of the bcm as far as interpreting and acting upon these switch position messages. But you might try reading the resistance between pins 1 and 2 of the ignition switch when the key is in each of its various positions and also when the key is out. It might be for example that the key 'in' contacts are flakey which would throw off the resistance and thus the interpretation. Have you tried pushing in or from side to side on the key when you have the engine running to see is that might jar the non-working systems into action?
Also check to see if you get reliable continuity between pins 5 and 3 of the ignition switch in both the run and the start position, and no continuity in the other key positions. I wonder if those systems might be flaky because the body computer turns them off when you try the starter, only it thinks you are trying the starter when you actually have it in run.
And you might try spraying some constact cleaner into the inside of the ignition switch and then try putting in/removing the key, and putting the key in all the various positions of the switch.
Other than that, we are into a 'can of worms' at the body module proper.
Roland
PS Thanks for the rating and nomination
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QUESTION: Thanks for your help Roland and your welcome for the nomination, Its the least I could do. Just wondering if you have any insight as to what the rear wiper scenario has to do with this and what it could mean? Just seems very odd to me. Thanks again!
ANSWER: Hi Rob,
I looked into the rear wiper and find it a bit opaque. The bcm is involved in two ways with the rear wiper: the motor is controlled directly by the bcm. The washer pump is controlled by the bcm sending a pci bus message to the front control module which actuates the washer motor. So try to separate those and let me know which action improves the items that don't work. Also, do you have the auto temp control HVAC or the manual? The wiper controls are handled differently as to where they are located. Where is yours located? I mention opaque because so far I can't find the wiper switch in the wiring diagrams! I'm working with a CD which makes it less convenient.
Roland
PS: The one factor that ties the non-functional units together is that they are powered by the Accessory Relay (except for the 'blower', but you didn't mention which blower, front/rear/both, which might be relevant). So you might listen/touch the relay as you try the various permutations to see if that relay is clinking in and out, or if perhaps the current that it can put out is limited do to a short of some sort.
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QUESTION: Hi Roland, Well I tried what you suggested with cleaning the ignition with contact cleaner and it did not help the problem. The rear washer is definitely what makes the system respond like it does and the van does not have any rear heat/ac system or blower unit. I have not had a chance to run any tests on the ignition yet. I don't recall if I had mentioned that the wiper blades are included in this non functioning scenario also. As far as relays are concerned there is 1 that clicks in the fuse box [under the hood] when you turn to key on engine off. It will cycle about 6 times and the items will power up. It is 1 of the large fuse/relays, I will look and let you know which 1. Thanks for looking into my problem and making it your own.
AnswerHi Rob,
It has been over a year since you brought this problem to Allexperts. Just this morning another owner of the same T & C as yours brought the exact same problem to me. I wonder whether you might have resolved it and if so can you tell me how that was accomplished? Thank you for taking the time to answer me!
Roland
Immediate past answer in 2011:
Hi Rob,
I'll await the results of the measurements of the switch. It is difficult to understand why this discrepency exists between when the engine is running vs when it is not. The only other reason I can think of is that the voltage on the system may be different perhaps due to something with the voltage regulation of the alternator ouput that is internal to the pcm. So check to see what the voltage at the battery appears to be with the engine running and not running.
Other than that, I don't have a theory. For some reason the bcm 'sees' things differently, to either activate or fail to activate the accessory relay which is needed to be activated for those functions. However the HVAC blower motor is not related to the accessory...so that may be something to think about.
But since it seems to be an absolutely fixed false response that makes me think the ignition switch contacts may not be the problem. The only thing I can find out about the rear washer is that the bcm activates it by sending a message over the pci bus to the front control module telling it to activate the rear washer motor. Why that then activates the accessory relay(which is what I assume happens) is obscure to me
