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Discussion Starter #1
Hi all.
Fuse number 2 (5a) under the bonnet keeps blowing. Diagrams say this is an “additional coolant pump relay J496 - 30”. Can anyone tell me what this is please?

Another fuse, number 33 also says additional coolant pump relay but J496 - 87. What’s the difference? That one hasn’t blown.

I’ve tried a 10a in slot 2 & that blows too but a 15a doesn’t blow.

No water is being pumped into the expansion tank even with a 15a fuse in it. Can anyone help please?
Thank you.
 

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I’ve tried a 10a in slot 2 & that blows too but a 15a doesn’t blow.
Please don't do this. The fuse rating is selected to match the size of the wiring. If it was originally 5A then the wiring is big enough to carry up to 5A without overheating. If you put a 15A fuse in, you risk damaging the wiring loom - and that can be very expensive to fix (because if it fails with a short to another conductor you won't know where the failure is).

The first thing to check would be the pump itself. If it is seized then it is likely to be pumping no coolant and taking too much current. You don't say what van you have, but generally the additional coolant pump is under the van, below the passenger's feet on a RHD vehicle.
 

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Discussion Starter #3
Sorry. It’s a 2L T32 4motion.
Do you know why there are 2 fuses for the pump?
 

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I haven't looked in any detail, but I would expect the one with -30 after it to be a permanent connection to the battery, and the other to be ignition-switched. You could (obviously) confirm this with a multimeter on the supply side of the fuse while the ignition is off.
 

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If we are talking about fuses SD2 & SD33, (located in the fuse box to the side of the battery) then SD2 is the "control" side of the relay J496. It doesn't need to be big because it is only operating the relay coil. The contacts within the relay carry the larger current required for the additional coolant pump.
As Triffic has said, replacing this with a 15A fuse is asking for trouble !!

There is a residual heat relay somewhere, (J708) which I presume controls the operation of relay J496, which in turn operates the additional coolant pump should the coolant temperature/engine be above a certain level.

If fuse SD33 (listed as 5A on my drawing) is not blowing then it would suggest your fault is in the "control" side of this electrical circuit rather than the pump side.
As a starting point I would try & locate relays J496 & J708. If you remove them both see if the 5A fuse at SD2 still blows. Do NOT put any fuse bigger than that in this position !
If it doesn't fit the relay J496 first & see if it blows. If it doesn't blow try refitting relay J708 & see if it blows then.
Depending upon when the fuse blows will narrow down where your actual fault lies. Be very careful doing this as the last thing you want to be doing is causing additional problems. If you are at all unsure get a "propper" auto-electrician to look at your problem, it may well work out far cheaper in the long run !!
 

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It's possible relay J496 is inside the E-Box, under the battery, on a relay carrier within.
Relay J708 is most likely inside the cabin, possibly under the dash somewhere. Sorry, that's as accurate as I can be.
 

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Discussion Starter #7
Thanks Cat3. Not sure any auto electricians will come out in the near future. I’ll try what you said and see what happens.
 

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Certainly additional coolant pump failure is v common on 2.0 TDi Tourans, so imagine it likely for a T5, tho in the Tourann the add pump is under the wheel arch. My local VeeDub specialist garage is still working :). Sadly, I'm helping keep him in business!
 

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Discussion Starter #9
There’s a sound now from the front nearside wheel arch. Sounds just like when the wife’s water pump failed on her car so I’m guessing it’s in need of replacement. Would this be the cause of the blown fuse does anyone know?
 

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coolant pump 2 on the 2.0 is bottom centre of the engine. I think theres a design fault in the loom and it rubs through and shorts out, when I bought my van it had already been repaired and a new single core had been run from the e-box right down to the pump to bypass this.
 

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Discussion Starter #11 (Edited)
Thank you. It’s booked in at a local garage on Friday so I’ll see what they say before I part with my £250 they quoted and I’ll let them know about that wire too
OR
is the aux water pump easy to replace? So I can save myself some money. Can’t see anything on here or online about the T5.1 aux pump replacement, just loads on T4’s.
 

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Discussion Starter #14
I decided to leave it to the professionals and get it changed at the garage. I’ve just picked it up and the noise is still there, turns out it wasn’t the water pump but something right under the van sort of under the front passenger seat area that was vibrating. Oh well. I have a new pump now I suppose. I asked the mechanic to inspect the wire as mentioned above. He said the wire looked fine and fuse number 2 is now not blowing so might have re-jigged the wire back into position or moved it away from what it was shorting in for now.

I have another question though...

In the expansion tank, should the water be circulating down one pipe through the engine and back into the tank from another pipe? My water is still & not flowing. Is this right? Just don’t want to take it back and look stupid in front of the mechanics. Thank you.
 
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