Delay Wipers = weird

[Joe Mc]

When wipers are on delay they stop mid-way for a few seconds then park at bottom of windshield then go up and pause mid-way. What's going on? Need a new motor or something in the delay system? They work fine when on low or high.

 

[Joe Mc]

Forgot to mention, same thing happens when I push washer = wipes 3 times then will stop about 6" after it reaches full vertical on way back down. It'll sit there forever, if I turn on wipers to low and let them cycle a few times and shut off when they reach full vertical they'll park at the bottom as they should. Anyone???

 

[DavidC]

I believe you have a service manual Joe. Section 8K-4 lists trouble shooting, you will need a meter. If you need further help let me know. It is probably the best way without throwing parts at it, just take your time and hopefully you have a warm place to do it.

Dave

 

[Joe Mc]

Hey Dave! Happy Thanksgiving to you and yours. Yep I do have a manual and will check out "section 8" (Klinger from MASH was always trying for one...) and see what I come up with. As far as a warm place...not presently, so I'll wait till Saturday to get out and meter some points.

 

[DavidC]

Hi Joe, Happy Thanksgiving to you and yours also. Let us know if you find something, could be as simple as the relay in the PDC (would be nice).

Dave

 

[Joe Mc]

Hey Dave,
Haven't made time to check manual or truck related to delay wiper situation. I'm not the best electrical trouble shooter for sure, at best I can fix electrical things but when it comes to troubleshooting I'm weak and, unfortunately, the wiring diagrams in the SM confuse the heck out of me. Any suggestions for me I.E. go to panel located ___, read (OHMs or DC Volts) from pin#__ or wire colored __ to pin__ or ground - you should get ___ OHMs or ___ DC Volts if good or if not problem is/could be? Sorry, thanks for reading.

 

[DavidC]

Give me a little time as I will look it up again and try to guide. The only thing I do not know but will try to find is this module that gets signals. Has to be somewhere that gives the location.

Dave

 

[DavidC]

Ok, the mysterious integrated electronic module is really the Central Timer Module. If I had to assume where the problem is the timing Module would be it. I believe it is under the knee bolster. I see them on ebay used, probably can not find new is my guess. Now I can get to the rest.

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[DavidC]

Info 8K-6 and 7

 

[PBJ2500CTD]

Joe,
Easiest first step would be swap out the wiper relay in the PDC with another similar relay from the PDC.
The wiper park function is determined by the position of the multi-function switch, wiper motor position, the sensing of the CTM and the wiper motor relay state. The CTM along with the wiper knob on the multi-function switch is where the timing of the intermittent wipes are determined.
Since the wipers appear to properly park when you manually turn the wipers off, the motor park switch would most likely be functioning properly. Most park issues are caused by this switch.
Do your wipers vary in time throughout the wiper knob positions?
This would leave the relay (1) or CTM(2) or a wiring issue(3) as the culprit. I will follow the circuits a little more closely and see if the multi-function switch may have an effect, or the motor park circuit contacts may have an open spot.
Using the KISS principle, try the relay swap first.

 

[DavidC]

Think I read there was not another relay like this one.

 

[PBJ2500CTD]

Thanks Dave for the detailed info.

 

[PBJ2500CTD]

Should be able to swap any of the mini relays. Here is the IPB for the PDC: See Item 2

 

[DavidC]

The CTM does provide the ground for the relay coil which would switch on and off from the CTM internal timer. Maybe the muti function delay has a defective system losing the signal to the relay

 

[DavidC]

Don't know if this applies

 

[PBJ2500CTD]

Looking at the wiring schematic in a little more detail the relay is the most likely culprit. It would supply the park voltage after the intermittent signal starts the motor rotation. The motor and relay positions determine the activation of the park circuit. The symptoms you are experiencing are indicators that the park cycle in the intermittent mode is not being activated. I still would not rule out 100% on the multi-function switch or CTM.
I don't know what series level your truck, standard, SLT, or SLT+, but on my 02 SLT+ there are three different CTMs, depending on the option configuration. They are no longer available from commercial sources (dealer, parts stores, etc). I have had alarm issues with mine and have to live with it, or find a source and take a wild chance that I will not inject a multitude of other issues since it controls lots of stuff.

 

[PBJ2500CTD]

Dave, Do you have the second page schematic showing the wiper motor and relay?

 

[DavidC]

This one ?

 

[PBJ2500CTD]

Yes. Thank you. Easier to read than juggling the big book and a laptop on my lap.

 

[fest3er]

Hmmm. I don't think the relay controls the delay function; those relays (of the same size/footprint) are all interchangeable, so it's easy to test.

The CTM should only power the wiper long enough to get it started; the motor should have an internal circuit to power itself until it reaches 'home'. Note the diodes in the diagram; they're a strong hint that voltage/current from the motor must needs be blocked.

I suspect the culprit is the wiper motor because only the motor itself knows 'where' it is and when to stop. It almost certainly has internal low-tech 'rotary' circuitry to keep the motor powered until it reaches 'home'. If your wipers 'hide away' (park) behind the hood, there's a separate circuit and internal control to make the wipers do this. If you open the wiper motor, you'll likely find that the contact surface that keeps the motor powered until it reaches 'home' has a break in it that causes the wiper to stop mid-stroke.