Idle Speed Motor Harness

[bruscreen]

I'm trying to replace the idle speed motor on 5316, but I've hit a bit of a snag. It seems a Prior Mechanic replaced the stock unit with a Bosch "0 280 140 202", a VW part with only 2 wires. The 2-wire harness spliced into the original harness' black/white wire and ran to the engine for ground. The black/red and black/green wire were cut and taped off.

I'd love to find a harness that I can just splice in, but barring that, can someone tell me in which order the wires belong? The new idle speed motor has the connectors labeled 3, 4, and 5 if that helps to get a common point of reference.

[Ron]

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[bruscreen]

Thanks Ron! Looks like what I saw as white (in poor lighting) was supposed to be pink, and goes in the middle. That gets me to 50/50 odds of getting the order right, if I build my own connector.

[DMC5180]

Thanks Ron! Looks like what I saw as white (in poor lighting) was supposed to be pink, and goes in the middle. That gets me to 50/50 odds of getting the order right, if I build my own connector.

Bruce, Just in case you want a NEW connector. http://www.efiexpress.com/catalog/product_info.php?cPath=7&products_id=62&osCsid=a8f14f31fd7c2219d745fba3c751b36b

[bruscreen]

I wasn't expecting the connector to be so standardized - figured I'd have to go looking for junked Volvos or something. The plan is coming together!

Now that I'm (more) awake, reading the diagram again, I notice that the pins at the other end of the wires are labeled 3, 4, and 5. Hoping that's not a coincidence.

[Ron]

Had a chance to check-

Looking down into the harness plug with the single notch turned up, where you can see the contacts, it goes:
Black/Red, Black/Pink, Black/Green (left to right).

[Delorean Industries]

DPI can vouch for the connector quality. While it is not an actually Bosch replacement it is molded from such. This is the same connector that we use on our new harnesses for stock PRV applications.

[bruscreen]

Status update:
I got the new plug and wired it in, but it didn't work. I went through the circuit and tested every component, it's all good except that the ECU doesn't provide power to the idle speed motor. Terminal 4 gives +12 measured against ground, but it's less than one volt against Terminal 3 - fluctuating slightly whether the coil RPM pulse is connected or not - and nothing at all against Terminal 5. Looks like time for the solid state ECU upgrade. This is probably why the system was modified in the first place.

[Bitsyncmaster]

You will need the three terminal type idle motor to get things working. Center terminal is driven to +12 volts from the idle ECU (you can not run 12 volts from elsewhere since the idle ECU has diodes to clamp noise). Then the other two terminals are driven to ground through the idle ECU. There is no ground connection on the idle motor.

I use a volvo idle motor which has the same 3 terminal connector. I found this volvo unit works better than the stock unit. Moves the valve much smoother and draws half the current.

[bruscreen]

Sorry, I may have forgotten to mention that I only realized the wiring had been modified when I went to connect a new three-wire Bosch 0 280 140 520. This is what I have connected to the ECU, and the connections have been tested with only 0.4 ohms of resistance.

What does the ground connection through the ECU look like on a multimeter when it's working correctly? If I unplug the motor and hook the multimeter up to the wires, then use the idle screw to adjust the idle out of spec, I figured I should see something close to 12 V difference between the center and the outside wire? What I get is under 0.5V on one side regardless of the idle speed, and nothing ever on the other side.

[Bitsyncmaster]

Sorry, I may have forgotten to mention that I only realized the wiring had been modified when I went to connect a new three-wire Bosch 0 280 140 520. This is what I have connected to the ECU, and the connections have been tested with only 0.4 ohms of resistance.

What does the ground connection through the ECU look like on a multimeter when it's working correctly? If I unplug the motor and hook the multimeter up to the wires, then use the idle screw to adjust the idle out of spec, I figured I should see something close to 12 V difference between the center and the outside wire? What I get is under 0.5V on one side regardless of the idle speed, and nothing ever on the other side.

You should read a DC voltage of between 0 and 12 volts on one pin and the other pin should be the oposite (2 volts on one pin and 10 volts on the other). The DC voltage is an average of the switching signal. If you checked for AC voltage I think you should see about 12 volts on each end pin. I have not checke it with a meter (I use an O-scope) so that is what I think you should read.

[bruscreen]

There was definitely something wrong with the original idle ECU. I installed the solid state ECU last night and now have idle speed control. Thanks again guys!