Changing the Heated Rear Window (HRW) on a Mk1 to accommodat

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Changing the Heated Rear Window (HRW) on a Mk1 to accommodat

Postby Matt C » Sat Oct 17, 2015 8:32 am

Hello again folks,

Just another quick query to see if anybody has done this and can highlight pointers/pitfalls in advance?

I have standard 1993 Eunos with the Perspex window (on a ripped roof). As part of a restoration I'm replacing this with a complete roof with HRW from a Mk2, supplementing it with a hardtop with HRW, also from a Mk2.

I have traced the existing 'dormant' loom behind the dash, plugged in an OEM HRW switch, added a 10A fuse to the fuse-holder by the electric antenna, and fitted an LA10 relay onto the loom by the boot-release.

In theory, that should be the circuit established. What I want to do is change the vehicle's loom socket from a Mk1 to a Mk2, so that it will accept the existing harnesses on the rag and hard tops (the other option was to buy two Mk1 harnesses....at £150!)

Im guessing it is as simple as cutting the three wires going into the existing plug, and soldering the new plug in place. HOWEVER, the colour-codes only match on two of the wires. Is it a 'safe bet' that the third wires mate up, even though they are coloured differently?

Other than that, can anybody else see anything which I might have missed out, to get this circuit working? (I'm working on another 'electrical gremlin' at the moment, so I can't test this circuit)

All help very gratefully received, folks!


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Re: Changing the Heated Rear Window (HRW) on a Mk1 to accommodat

Postby mgrays » Sat Oct 17, 2015 10:14 pm

I did this about 10 years ago.. seem to remember the Mk2 was 3 wires but Mk1 was 2 wires as the Mk2 has a switch to stop the window heating if the roof is down ... the Mk1 could only have a heated hard top so there was no need. So a bit of wire tracking is needed.. the heated window does not care which way around it is but third switch wire does matter as it must interrupt the relay. The way I got a Mk2 plug was to get it cut off a Mk2 car in a breakers.. Hope that helps... car is in storage a few miles away!
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Re: Changing the Heated Rear Window (HRW) on a Mk1 to accommodat

Postby Matt C » Sun Oct 18, 2015 5:53 pm

That's brilliant, thanks!
The harnesses for the soft-top and hard-top are present, so no issues there, just a case of changing the mk1 plug to a mk2 plug at the 'car' end of the connection. Both have three wires, two of which marry up colour-wise.


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