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Auxillary coolant pump not getting power.
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HearseLady1966
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PostPosted: Wed Jul 12, 2017 2:51 pm    Post subject: Auxillary coolant pump not getting power. Reply with quote

The 93 i am working on has a brand new Auxillary pump for the coolant. It works fine as i tested it with a battery. However it is not coming on after the engine is shut off. I tested for power at the connector and there was none. Is there somewhere i should check first for this? I tried testing it with key off, key on and just after we shut the engine off (when it should be running) and nothing.
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mvaska
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PostPosted: Tue Jul 18, 2017 10:11 am    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

aux coolant pump doesn't always come on. engine has to be pretty hot in my experience to have it run after shutting off.

are you sure the conditions are correct for it to even run the aux pump? you might be looking for an issue that isn't there. Smile
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Abscate Premium Member
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PostPosted: Tue Jul 18, 2017 10:41 am    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

Get the wiring diagram and see if it is wired hot and switched ground or the other way around. If one of the wires goes to a ground point nearby, then it is switched hot.

Ill confess the wiring diagram for my 2002 afterrun cooling pump is a real weirdo, so I won't take the lid of that barrel of monkeys here.
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Joshwa
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PostPosted: Tue Jul 18, 2017 1:16 pm    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

The after run pump wiring is pretty simple. The single circuit on 123 below. It just relies on the temperature at the coolant temp sensor to operate, with the ignition turned off. I don't know what temperature it activates at, but I agree with mvaska that it has to get very very hot before it operates and not every time you shut off the engine.

The circuit is: fuse <-> relay (to shut off power during operation) <-> thermal switch (on upper coolant hose) <-> pump <-> ground.

I think that you could test continuity by jumping the wires at the thermal switch with the ignition in the off position. If it runs, it a matter of if the sensor is not hitting its threshold or not working. If it doesn't, test along the circuit components to see where power missing. Here's the wiring diagram which will probably be more self explanatory.


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93 Weekender TDI conversion (AHU)
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Abscate Premium Member
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PostPosted: Tue Jul 18, 2017 7:10 pm    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

I'll post up the 2002 version but what's up with the single block having two componen t designations, F95 and G2?
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Joshwa
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PostPosted: Tue Jul 18, 2017 10:00 pm    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

4 wire plug to the coolant temp sensor and thermal switch. The sensor moves the coolant needle on the gauge cluster on a 93.
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PostPosted: Tue Jul 18, 2017 10:26 pm    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

Similar for a 99 EV, except that the there are two legs to ground through the power relay and the thermal switch.


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Snowshoer
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PostPosted: Wed Jul 19, 2017 3:12 am    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

On my '99 the pump doesn't run all the time. When it does it is not on very long. You can turn the key to the "on" position and listen for the pump to run to make sure it is getting power.
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PostPosted: Wed Jul 19, 2017 4:04 am    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

Looking at the diagram above that is seriously messed up.

There are some open circuits and missing components that don't make sense

Specifically , how F18 works into that, the relay looks like it closes on fuse S19 being hot and thus the coolant overrun pump is. On constantly.

I saw the same weirdness on my 2002 version.
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Joshwa
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PostPosted: Wed Jul 19, 2017 6:29 am    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

Yes, the auxiliary pump has possible power to it all the time and will operate depending on the temperature at the thermal switch when the ignition switch is off. The relay placement does look confusing. It looks like the pump would be running whenever there is ignition power.
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TDCTDI
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PostPosted: Thu Jul 20, 2017 3:52 pm    Post subject: Re: Auxillary coolant pump not getting power. Reply with quote

Check fuse 15 & 19. If I remember correctly, the after run pump shares a current track with the cooling fan control relay (track k) which in turn won't allow the A/C compressor to work.
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