ABS motor connector oddity

H

HelluvaEngineer

Registered User
I just put in another rebuilt ABS pump motor. When connected directly to the battery via the motor connector and some jumper wires, while completely installed in the car, it runs just fine. The other side of the connector is getting about 11.7 volts (about same as the battery when the car is not running).

When I plug the two connectors together, the motor will not run.

What could this be? It's like the motor is not getting enough current to run.
 
Check the pinouts.

Duffy Floyd had a note once about a change where the pins were about 90 degrees off from one year to another in the connector - that is, year "A" with motor from year "B" wouldn't run.

Lemme see if I can find that ...

Nope, my GoogleFu is lacking today. But I DO remember reading that.

I'd probe the connector from the car both ways and see which pins have power, then pin the motor and see which pins have continuity.

RwP
 
Imagine the flat part of the connector is at the top. I verified that on the female side, 12v+ is at the top and bottom, ground is on both sides. At the pump, I energized it by putting + on on of the top connections, - on one of the side connections.

Oh, I also tried jumper wires between the connector halves. That didn't work.
 
Use the jumper wires and measure the voltage when it's trying to fire.

Could be bad contacts on the pressure switch and/or the ABS relay (excessive resistance, the meter doesn't pull enough current to drop the voltage, the motor does.)

RwP
 
RalphP said:
Duffy Floyd had a note once about a change where the pins were about 90 degrees off from one year to another in the connector - that is, year "A" with motor from year "B" wouldn't run.
Click to expand...

I've experienced that on two different occasions....

In each case, the motor would run backwards (it is a DC motor after all)....:p

I re-wired the terminal on the motor side and the pump would spin in the correct direction....:D
 
the-big-e said:
I've experienced that on two different occasions....

In each case, the motor would run backwards (it is a DC motor after all)....:p

I re-wired the terminal on the motor side and the pump would spin in the correct direction....:D
Click to expand...

That may have been you with that note, I dunno.

RwP
 
RalphP said:
Use the jumper wires and measure the voltage when it's trying to fire.

Could be bad contacts on the pressure switch and/or the ABS relay (excessive resistance, the meter doesn't pull enough current to drop the voltage, the motor does.)

RwP
Click to expand...
A couple of observations. I put the voltmeter in parallel with some jumper wires. The voltage dropped to 0.01v when I put the jumpers on the motor.

There is no resistance between the + and - motor connection. I haven't studied dc motors in a while. Is this an issue?

I also pulled off the connector on the pressure switch and reconnected it. It looks fine.

For some reason I am very suspicious of the relay at this point. Thoughts?
 
Pull the relay and apply power to the two large terminals of the relay.....

You will here and feel it click if it's good....
 
the-big-e said:
Pull the relay and apply power to the two large terminals of the relay.....

You will here and feel it click if it's good....
Click to expand...
I'll try it today. I'm also thinking it should be possible to jump the connections at the connector if I can find the right locations. That may be a better test for the relay.
 
based on the continuity test in my shop manual, the relay is bad. It should be normall closed but it looks like it's not making contact. I'm picking up a replacement tomorrow morning.
 
Replaced the relay. Now when I turn the key, I hear the relay click. 0V at the pump. This makes me suspect that the pressure switch is also bad. I will test the new relay, then pull the connector from the pressure switch and jump it.

I believe you can ground pin 4 or something? Also saw a quote to connect pink/blue to gray - this may be the same as grounding to chassis, not sure.
 
Could pull the pressure switch connector and use a bent paper clip to bypass.

If that kicks it on, it's a safe bet the pressure switch is bad.

If it doesn't, that's not the problem (it may be A problem, but it's not THE problem.)

RwP
 
OK, this picture was a little hard to capture. See attached. I jumped the connections marked in red with a paperclip. This was pink/blue and grey. I need to check my wiring charts but I read this online. The pump immediately kicked on.

So, assuming I'm not missing something, does anyone have a good pressure sender for sale?

FWIW, so far, new pump motor, new accumulator, new relay, new pressure sensor. Would have been better off getting a rebuilt and tested unit. Or scrapping the ABS.
 

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Thanks for the follow up. Yeah, I got everything back in this weekend. This time I was a little smarter and connected all the wiring to test before actually installing in the car. The motor kicked right on.

I drove the car to work this morning. So far so good.

FYI - the impedance test (bench test) of the old sender indicated that it was OK. IMO it's important to jump the connector in the car to test the state of the sender.

Thanks everyone for all the help.
 
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