Electrical Experts - Intermittent Relay Operation

[Iciclehead]

All,

Been doing some work on the electrical harness to get it ready to put it back in the car.

I have been playing with the intermittent relay as I have a spare and I was hoping to use it to make the rear wiper intermittent, but I can't seem to figure it out.

Diagram is as below:



So,

E - wiper/washer switch
V - wiper motor
J31 - Intermittent relay
E38 - Intermittent relay potentiometer
V5 - washer pump

So, the easy part on the relay.

In the off position, the wiper park circuit (53a) is energizes the motor V through the relay pin 31b, then to pin 53, through the wiper stalk switch through 53e, out through 53 and then to the wiper motor to allow it to park

Turning the intermittent knob E38 routes power through 15a and 15b (relay and potentiometer) which times the delay, activating J31 relay to then connect power through relay pin 15, out through 53, through the wiper stalk/wiper motor pins 53, kicking the wiper motor off of park position.

I am presuming that once it gets kicked off of park, the transistor in the relay de-energizes the relay, and the wiper motor then does one sweep with power through the off position circuit.

What I can't figure out is what the heck pin 86 is doing. It looks like it only gets power if the washer pump is activated, but that makes no sense.

I did a bench hookup as follows:

Potentiometer

Pin 15 - 12v
Pin 15a - to 15a on relay
Pin 15b - to 15b on relay


Intermittent relay

Pin 15a - to 15a on potentiometer
Pin 15b - to 15b on potentiometer
Pin 31 - ground
Pin 53 - test light connected to ground
Pin 31b - not connected (theoretically the off position so no current unless the wiper has not finished parking)
Pin 15 - 12v
Pin 86 - tried both 12v and ground

Result was:

Pot off - test light off
Pot on - test light comes on after a delay, dependent on how far the knob is turned....the more clockwise it is turned, the longer the delay is before the test light comes off, but it does not turn off. It just stays on until you turn the pot off.

No smoke or nastiness, I tried both of my intermittent relays with exactly the same result.

So, the issue is pin 86 - what does it do? It does not make a difference if it is connected or not connected, also does not make a difference if it is connected to 12v or ground.

I expected that the test light would come on for a second or two and then go off for a delay, then back on and off consistent with the setting on the potentiometer...but it just comes on and stays on.

What am I missing?

Thanks all...

Dennis

[jbell959]

Looks like pin 86 should be hot when you activate the washer pump so the wipers also come on

[Iciclehead]

Originally Posted by jbell959

Looks like pin 86 should be hot when you activate the washer pump so the wipers also come on

That is what I thought too....but on the bench, connecting 86 to power or ground does not make a difference and does not give me the intermittent test light on/off I expected.

I also understood that the transistor in there needs three connections - source, drain and gate.

I guess I figured that three connections were 15a, 15b and 86 as that is what the wiring diagram seems to depict, but there are undoubtedly more components in there that give the intermittency.

The fact that the wiring diagram shows 86 only connected when the washers are activated makes sense for a "wipe on wash" functionality which I did not think 911's had, but given you are not washing, then I would have still expected there to be an electrical source.

Does not make sense to me yet...

Thanks though!

Dennis

[jbell959]

What is the part number of the intermittent relay you are using? I'm sure there is more inside it than what they show in the picture. They always simplify the components in the schematics. I'll see if I have a spare one and I'll open it up.

[Iciclehead]

Originally Posted by jbell959

What is the part number of the intermittent relay you are using? I'm sure there is more inside it than what they show in the picture. They always simplify the components in the schematics. I'll see if I have a spare one and I'll open it up.

Good add, both are the same 911 618 149 01 (SWF)

Thanks

Dennis

[mysocal911]

Originally Posted by Iciclehead

I also understood that the transistor in there needs three connections - source, drain and gate.

The transistor type is a germanium PNP. There're two, and can be replaced with silicon PNPs.

Originally Posted by Iciclehead

The fact that the wiring diagram shows 86 only connected when the washers are activated makes sense for a "wipe on wash" functionality which I did not think 911's had, but given you are not washing, then I would have still expected there to be an electrical source.

Right, 86 provides an additional power for wash mode.

[jbell959]

Sorry, I couldn't find an extra relay to pull apart

[Iciclehead]

Originally Posted by jbell959

Sorry, I couldn't find an extra relay to pull apart

No worries, thanks for trying...

Dennis

[Iciclehead]

Ok, I made some progress on the intermittent relay operation side of things.

The operation of the intermittent relay is entirely controlled by pin 31b.

In the normal off position (wiper at rest) 31b connects through the wiper motor pin 53e, through the contact plate in the wiper motor assembly to ground, so when the wiper switch is OFF and the intermittent potentiometer is off, then 31b is grounded.

When the intermittent potentiometer is turned on the relay is enabled/switched/activated so that power flows from relay pin 15, through relay pin 53 and from there to the wiper motor, 31b is now disconnected from ground and if left in disconnected from ground, the relay will continue to be enabled and power will continue to flow from pin 15 to 53 and to the wiper motor and not switch off. I believe this is the wiper motor power during intermittent operation which will continue the sweep until....the following

As soon as 31b is reconnected to ground - which happens when the wipers reach the park position, the relay is disabled and returns to the state in the diagram (wiper motor 53e grounds 31b), no power to the wiper motor.

Depending on the setting of the potentiometer, after an interval, the relay is again enabled and the cycle repeats itself:

1. Power to wiper motor through relay pin 15, out through relay pin 53 to wiper motor pin 53, 31b disconnected from ground as long as the wipers are off of the park position.

2. Wiper park position reached, 31b again grounded through the wiper motor pin 53e, relay deactivates and the wiper stops.

3. If potentiometer still on, then off we go for another wipe at the appointed time.


Now, the issue for the rear wiper in this situation, is that the rear wiper pin 31b connects to POWER at the park position through an internal connection to wiper motor pin 53...not ground.

As can be seen in the circuit diagram...



I have been looking at the little leaf connections in that motor and do not see an easy way to change that....it is conceptually easy but practically difficult....

More research to come...like maybe putting a relay in the rear wiper circuit....just what I need...another one of those blasted relays hanging around.

Dennis

[Iciclehead]

Oops, forgot to include the rear wiper wiring diagram....




You can see on V12 the connection from 31b through an internal connection (in reality a little brass contact plate) to pin 53 which is connected to power.

When the rear wiper is turned on, then the brown/white wire is disconnected from ground, power flows through 53 to make the motor run.

When the wiper is turned off and off of the park position, the wiper motor maintains power through 53a, through the internal connection to 53, with 31b connected to ground but not connected internally through the wiper motor assembly.

When the park position is reached, then the contact that joins 53a and 53 separates, cutting power to the motor, 53 is now grounded through 31b which seems to help the motor stop more quickly and prevents the momentum of the motor from spinning past the park position and causing the wiper to cycle once more.

I tried it with 31b disconnected and more often than not, when 53 was disconnected from power it would just pause at the park position, rotate past it, then powered through 53 a do another cycle over and over again.

As soon as you connect 31b to ground it stops promptly at the park position.

Now, just thinking through that new relay I think I need.

Dennis

[Iciclehead]

OK guys, it is all hooked up and running on the bench. I now have an intermittent rear wiper capability using the stock relay and potentiometer.

I may post pictures later if there is any interest, but here is the pin connections.

Potentiometer

Pin 15 - 12v (can share with relay pin 15 to S14 in front fuse box)
Pin 15a - Pin 15a on relay
Pin 15b - Pin 15b on relay


Relay

Pin 15a - to pin 15a on potentiometer
Pin 15b - to pin 15b on potentiometer
Pin 15 - 12v (can share with potentiometer to S14 in front fuse box)
Pin 31b to Pin 53 on rear wiper motor (note change on motor)
Pin 53 - direct connect to rear wiper motor - new connection on rear wiper motor
Pin 31 - Ground
Pin 86 - not used (for wipe on wash)

Rear Wiper Motor

Pin 31b - Pin 31 on rear wiper motor (Ground) via jumper wire
Pin 31 - Ground
Pin 53a - 12v (use S24 in rear engine compartment panel)
Pin 53 - Relay pin 31b (note disconnect pin 53 on rear wiper motor from motor terminal)
Motor power pin (new) - Pin 53 on relay

Besides figuring out how the heck this stuff all works, the big insight was that the intermittent relay only supplies power to the wiper motor through pin 53, so you need a direct connection as opposed to the standard rear wiper connection which gets power either by the dash toggle switch or via 53a in the park circuit...the rear wiper middle connector switches power while the intermittent relay circuit switches ground.

Anyway, a tiny little win....not sure why I really needed this, but it is something I wanted and I wanted to minimize the number of different components I use and keep the stock look. I will be modifying the logo on the potentiometer knob to look like a rear window.

Only thing left to do is to figure out the best way to connect that "direct to motor" wire as it is an extra connection (since 31b gets jumpered to ground), likely I will just put a small hole in the rear wiper case, put a nice tight little grommet in it and the have the wire hanging outside a little.

Very happy, electricity is not my thing....I figure something like 40 hours of fooling around where a good electrical guy would have taken at most 40 minutes.

Dennis

[Iciclehead]

Great...one more thing, I thought I had the 8 pin relay base for the intermittent relay I will be using....but I don't or at least cannot find it.

If anyone has one they are trying to get rid of, happy to buy it from you...

Thanks!

Dennis