Backfeeding hiccup

[Da67goatman]

I have recently wired in Delphi washer fluid heater so I don't have to wait half an hour for heat to de-ice my windshield.  I have a couple problems with this though. 

First is a ferocious buzzing through my stereo with the radio on but engine not running and my gauges do partial sweeps in sync with the buzz.

Second is I can't get just the sprayer to activate, the wipers always accompany them. 

I have isolated the power circuit with dedicated power/ ground wires from heater to battery and added a relay to the kick on circuit to further isolate.

I have tried running switched power right to the washer pump but it backfeeds and activates the wipers anyway. 

Who knew it would be so hard to just heat some fluid and spray it on the windshield.

Anyone have any suggestions on why or how these things are driving me crazy.  I have attached the wiring diagram for the washer/wiper circuits(lower right corner)

Anyone have suggestions and how to fix said problems, without removing the heater.

[VileZambonie]

What are we working on here? You posted a schematic for the next gen pickups

[Da67goatman]

Its a 1992 fullsize Blazer.  It has lots in common with the older gen but somethings are different.  For example i can't find a rear defrost wiring diagram anywhere.

[VileZambonie]

So you want the washer to activate the fluid pump only and the wipers to have to be manually turned on?

As far as the heater circuit you installed, ensure the wires and heater are not fashioned in such a way that they are creating RFI by being close to any other circuits, twist the wires, make sure your grounds are all clean and tight.

[Da67goatman]

Let me clarify, being flustered when I posted caused some crucial information to be left out.
I have installed a momentary switch that I want to use to spray heated fluid only, and still have the stalk work in factory configuration.  What I am looking for is: what circumstances allow me to use the washer pump without the wipers wiring wise. 

As for the buzzing and twitching gauges, it does this regardless of what input is selected on the head-unit but goes away if switched off.  The wires came twisted and I ran them directly to the battery across the firewall above all the factory wiring looms.  I ran a fresh key on exciter to a relay to kick on the heater when in the run position only.  If i kill the exciter everything is great except no heater obviously so I have diagnosed that as the source of the noise but have no idea how to fix it.

I was looking at trying some different noise filter options as I have Dash Solutions S-15-A DSF laying around, but once again I don't know where to put it.  I have some electrical knowledge as I had to rebuild the turn signal harness from rodent damage, but this is just outside my zone.  Thanks for your help

[VileZambonie]

I'll take a look tomorrow unless bd beats me to it one of us can draw you up a diagram.

[bd]

So the heater is always energized with ignition on... and the gauges convulse and buzzzzzzing is heard through the speakers until either the radio is turned off or the fluid heater is powered down?  It might be the heater thermostat cycling.  Can you guesstimate the frequency?

Do the symptoms change if you move/relocate the fluid heater power leads?  Any difference with the hood opened or closed?  Does the engine running or OFF have any noticeable impact?  Try to determine whether EMI/RFI is broadcasting or entering through the primary wiring.  Physically verify that the cab and sheetmetal grounds are perfect then attach a 1/4" or 5/16" braided ground strap between the hood and firewall.  If the symptoms are worse with the engine running, service all of the B+ connections at the starter solenoid, firewall junction block and alternator.  You can also try installing an MSD 8830 ignition noise filter in the B+ lead as close to the heater unit as possible.

The washer pump can easily be isolated from the wiper motor wiring using either a diode or garden variety Bosch style relay.  It seems to me that the "pulse" is the more troubling issue.

[Da67goatman]

Video

https://youtu.be/osC3dwLVxXA

[bd]

I have an engraver that sounds a little bit like that....

The hum sounds like ~60 Hz and, as suggested by the volt gauge in your video, occurs when the heater cycles on via its internal thermostat.  The cause of the hum in itself is curious, suggesting something equivalent to a multivibrator.  More than likely it's propagating through the primary wiring rather than broadcasting.  Although if the heater's current draw is high, it may be inducing the hum into adjacent wiring.  Nonetheless, the hum is so prominent....  As an initial recommendation, contact the seller or Delphi support in an effort to exchange it under warranty.

That said, thinking aloud, you may enjoy some success by rerouting the power wires across the radiator support through armored flexible conduit, bushed at both ends and thoroughly grounded.  Route the power leads away from other wiring and avoid parallel runs to other wiring.  The MSD capacitor linked previously may also provide some benefit along with a choke, depending on the current draw of the appliance.  If you have an oscilloscope, display the waveform.  Do you know the current demand of the heater?  All things considered, be prepared; by the time you're done experimenting, you may have an investment far greater than you ever anticipated.  You really won't know until you attempt a few suggestions, beginning with those bearing the lowest cost.

[Da67goatman]

Since its being such a pain, I'll just remove it all together. It's just not worth it for me to keep screwing with it.  Even if I got it working perfect it only heats the fluid to the windshield.  I'll look for a heating element I can put in the reservoir so no matter which squirter i use it's heated.  I'll crack it open at a later date to see whats going on inside.  Thank you.

P.S. how would I have wired the momentary switch to activate the squirter only?

[bd]

Based on your diagram...



...you can isolate the washer pump from the wiper motor circuit using either a diode or a relay.  The diode is the elegant approach requiring little space, but a relay maybe more to your liking. 

• Circuit Isolation Using a Diode - To select an appropriate diode, I'll suppose about three or fewer amps for the washer pump draw, so a 6-amp axial silicon diode should suffice (e.g., NTE5814 or equivalent).  However, that load specification is just my estimate without actually measuring the washer pump current.  The draw should be verified before purchasing and installing a diode.  Install the diode in series with the pink wire that connects the wiper switch to the washer pump.  Orient the cathode band of the diode toward the washer pump.  Now, insert the auxiliary washer pump pushbutton between fused B+ and the washer pump terminal, between the diode and washer pump.

Should you elect to use a garden variety 5-terminal Bosch style 12-volt relay, you have two options:

• Auxiliary Pushbutton Controlled Relay - Disconnect the pink wiper switch wire from the washer pump.  Connect the relay coil terminals 35 and 36, respectively, to ground and the auxiliary pushbutton.  Connect relay terminal 30 (common) to the washer pump terminal.  Connect relay terminal 87 (normally open) to fused B+.  Connect relay terminal 87a (normally closed) to the pink wire from the wiper switch that was previously connected to the washer pump.  Finally, connect the auxiliary pushbutton to fused B+.
  
  
• Wiper Switch Controlled Relay - Disconnect the pink wiper switch wire from the washer pump.  Connect the relay coil terminals 35 and 36, respectively, to ground and the pink factory power wire previously connecting to the washer pump.  Connect relay terminal 30 (COM) to fused B+.  Connect relay terminal 87 (NO) to the washer pump terminal.  Relay terminal 87a (NC) remains disconnected.

In all of the preceding scenarios, the factory wiper switch will still operate the wiper motor and washer pump as it always has, but the auxiliary washer pump pushbutton will no longer backfeed the wipers.  If my description isn’t clear, or you prefer a diagram, let me know and I'll sketch one up and post it.

I’m still a little surprised by the hum produced by that Delphi heater.  I wouldn’t have expected that from Delphi, especially since the unit is aimed at commercial truck applications of, which newer vehicles are loaded with electronics that are sensitive to EM/RF interference.  The hum is probably generated by pulse width modulation of the heater element.  Still, you would think they would have filtered the device to prevent noise injection into the parent electrical system.  Or, at the very least, included a remediation/troubleshooting guide with the product or online.  Disappointing!

Edit:  spelling

[Da67goatman]

Where should I be looking for diodes? When installing it: I need to cut the pink wire and solder the diode in between correct?

 Any suggestions on how big a heating element I should get?  The Delphi was 350ish watts and heated about a cup of fluid to 130f in 30seconds or so.

[VileZambonie]

How cold does it get where you are that you need a washer fluid heater? Have you tried a better washer solvent? you know they have different freeze points right?

[bd]

Where should I be looking for diodes? When installing it: I need to cut the pink wire and solder the diode in between correct?

 Any suggestions on how big a heating element I should get?  The Delphi was 350ish watts and heated about a cup of fluid to 130f in 30seconds or so.

I have no recommendations on a fluid heater.  I DO advise that you confirm the current requirement of the washer pump before proceeding in order to ensure you install a suitably rated diode (once you measure the washer pump draw, double that number for the minimum forward current specification of the diode).  Then Google "axial ___ amp 400 PRV silicon diode" or visit the company I previously linked in red.  Other sources are Radio Shack, Mouser, Frys and a myriad of others.  Any local electronics supply should have a suitable diode on the shelf once you know the appropriate value.

See the attached images for a modified schematic based on the diagram you initially posted plus a recommended method of installing an in-line diode so the leads are adequately supported.  Pay particular attention to diode polarity to avoid fireworks!  Frankly, I wouldn't carry the project any further without first settling on the availability and cost of an appliance that satisfies your need/want.  You should also be alert to the possibility that another brand of heater could just as easily introduce its own problems.