Fitting A Ph2 Coolant Expansion Tank....

[GLPoomobile 958]

Sorry for asking this! I could have gone outside and compared header tanks and wiring, but I'm a lazy c*nt. I figured someone on here would have an answer so I'd just ask instead

 

I've got a Ph1.5 and want to fit a nice new, white tank to go with the new washer reservoir and other bits. I've never liked the round tanks as they look stupid, so I fancied fitting a Ph2 tank (which now only comes in white from Pug). I know it will fit to the bracket, but what about the sensor?

 

I have a spare Ph2 tank with sensor, so no problem there, but I gather the wiring for the sensor is different. How would one go about adapting this to take the Ph2 sensor?

 

It's not a massively big deal really, but in addition to preferring the Ph2 tank, IIRC it's cheaper than the Ph1/1.5 too! Just want to know about the wiring before deciding which to order from Pug.

 

This is all I could find on the search (see, I'm not totally bone idle )

 

click me big boy

[GLPoomobile 958]

All watching Big Brother eh? Ya bunch of flippin' gayers

[Goliath 94]

watching what? my Big brother is at work so I couldnt be watching him

 

I though the wiring was the same, I seem to remember someone saying you just need to cut the plug off the end as thats the bit that dosent fit? I will no doubt be corrected soon enough!

 

 

P.S. apologies for the rather hopeless post!

[miamichris 9]

this is another question i was going to ask because im wanting to do the same thing when i get to that point in the rebuild!

 

so i don't have the answer, but i'll be reading it when someone more knowledgeable than myself finishes with big brother and explains it!

[pug_ham 244 3 Cars]

Both the sensor & the wiring is different, the plug has three wires to it where the phase 1.5 only has two but they are the same shape for the sensor.

 

Graham.

[Miles 331 1 Cars]

And it uses the big brown relay in the relay box on the strut top, It's the same as the 16v injection relay as odd as it may sound

[GLPoomobile 958]

So what do you need to do to make the Ph2 sensor work? If it's 3 wires it can't be that complicated, but someone must have an idea.

[pug_ham 244 3 Cars]

I tried swapping the wire order around on a friends car which they boughyt with a white tank & a working sensor but couldn't get the dash light to work.

 

It'd blow the fuse for the guages & rev counter when it dropped low on fluid but it didn't want to work like they should & I gave up on it once we'd cured the leak so it hasn't been needed since.

 

Didn't know they had a relay on the later cars though but then I've not stripped one that far back.

 

Graham.

[GLPoomobile 958]

f***'s sake

 

If you (Graham) couldn't get it to work then what hope has mong like me got?

 

I'll see if I can make any sense of the haynes wiring diagram, and then it'll have to be a case of go for the uglier and more expensive round tank, or the cheaper and better looking Ph2 tank but forego a working warning light

[pug_ham 244 3 Cars]

Its not that I couldn't figure it out but that I was only trying to get the sensor working as a temporary measure & we fixed the cause of the leak before I solved the sensor light riddle. Losing the rev counter was a fairly obvious sign the water might be a bit low.

 

Also not realising there was a relay in the system wouldn't have helped but it can't be that hard if we can get an accurate wiring diagram.

 

Graham.

[nick 3]

Hmmm... thats strange... I have gone the opposite way, I have put a round (phase 1) tank on my phase 2 (black square tank) and the wires just plugged straight in!

I only did it because I was sick of the annoying "light flicker" that most of the the phase 2's suffer from.

 

Nick

[welshpug 1,656]

I haven't yet found a diagram that has the 3 pin level sensor, but on a 405 you have; power, earth, and signal to dash warning light.

 

No relay in the circuit though but the power comes from the same feed as the instrument cluster and a few other sensors.

[pug_ham 244 3 Cars]

Hmmm... thats strange... I have gone the opposite way, I have put a round (phase 1) tank on my phase 2 (black square tank) and the wires just plugged straight in!

Thats what was done on my friends car before they bought it & it does plug straight into the sensor but the warning light doesn't work even with a working sensor for the earlier tank.

 

Does your low coolant warning light work?

 

Graham.

[nick 3]

Ah right, didn't know that, I'll check the light in a bit.

 

Nick

[GLPoomobile 958]

In the absence of a wiring diagram for the 3 pin sensor (I have taken on board your info above WP ), I think the best way to solve the mystery is to understand how the sensors work. I think I'm OK with the early 2 pin sensor, but not 100% on the 3 pin Ph2 sensor, so I'll tell you how I think it works and then see if anyone agrees or disagrees (remember I'm an electrical retard ).

 

Ph1/1.5 Sensor:

This sensor uses 2 wires. One comes from the fuse box, so I'm presuming it is the live, and the other goes to the instrument panel, so I'm presuming that is the earth. The sensor itself floats in the coolant, and remains open while the level is high enough, so the circuit is incomplete and the warning light remains off. When the coolant level drops too far, the float sinks and makes contact, completing the circuit, and allowing current to flow to the warning light. Light illuminates.

 

Ph2 Sensor:

This sensor uses 3 wires, which according to WP are live, earth, and signal to the light (but which is which?). The sensor is totally different from the earlier one, in that it sits at the bottom of the tank and uses two 'prongs' which are about an inch long, and protrude vertically up in to the tank. The prongs are about 1cm apart.

 

I'm assuming that these prongs conduct current, and that they use the coolant as a conductor to complete the circuit. So when coolant is present, current can flow from one prong to the other. When coolant is absent, no current flows. Or could it be that the prongs are using electromagnetic induction, or something?

 

If current was flowing constantly while coolant is present, then this is the opposite scenario to the early sensor. Would this explain the need for a relay? So while the relay is energised, it stays open so the circuit to the warning light is incomplete, and once the relay stops receiving current the switch closes and completes the circuit to the light.

 

But I don't understand the need for the 3rd wire.