Heated rear window problems

[Ken1958]

New here, but I have searched for info on this issue and can't see anything that correlates with this problem.

First off, I have Berkeley - last of the Mk1s, in fact this is no 397 of 400, so officially it is the 4th last Mk1, but I don't think Mazda UK numbered them sequentially. ;-)
These cars were pre-wired for the heated rear window so the wiring loom is already fitted.

Anyway, I recently acquired a Mk2 hard top for it and set about getting the missing parts and adapting the connectors.
So, I fitted the dashboard switch, put a 10A fuse in the box at the bottom of the aerial, and fitted the relay in the boot.

Then I searched online for how to connect the HRW, since the Mk 1 & Mk2 connectors are different. That's when it got confusing...

I found two DIFFERENT connection instructions!

Type 1 is shown here: http://www.mazdamenders.net/forum/viewt ... 114&t=6403
This has a direct connection between the top left and the top right, with the HRW connected between them and the bottom centre.

Type 2 is shown here, near the bottom of the thread: https://www.mx5oc.co.uk/forum/yaf_posts ... indow.aspx
This has a direct connection between the top left and the bottom centre, with the HRW connected between them and the top right.

So, before proceeding further, I checked the connections on the Berkeley.
Top left: 12V
Top right: 0V
Bottom centre: High resistance to 0V

So, it looked like this was wired to accept Type 2 connections. I cut the connector off the window loom and replaced the three wires with spade connectors. As expected, two of them were connected to one end of the HRW, the third was connected to the other end of the HRW. I plugged these in as per the Type 2 advice and it seemed to work - almost! The problem was that when I checked across the HRW it was only about 8Volts. I also noticed that the relay itself was buzzing. Something not right.

Reluctantly I then tried connecting as Type 1. As expected, this blew the fuse and nothing worked.

I went back to Type 2 connections and, after replacing the fuse, I am back with a buzzing relay - and some radio interference. Suspecting that the relay was faulty I removed it and checked, but it seemed OK, shorting the main contacts when only 6V was applied across the middle contacts.

Does anyone have any ideas why the relay is not making a consistent contact and buzzing? Any other ideas on how to wire this up correctly?

[Mazda Mender]

Hi

Either make one of the pig tails up on here or get a OE pig tail, something is not wired correct.
Just out of interest which switch is fitted...rocker type or push type.
M-m

[Mazda Mender]

This might be of interest....

viewtopic.php?f=114&t=6684
M-m

[Ken1958]

Hi

Either make one of the pig tails up on here or get a OE pig tail, something is not wired correct.
Just out of interest which switch is fitted...rocker type or push type.
M-m

Thanks for replying.

I've made up a pig tail as shown here as a test, with a light instead of the hrw: it's easier to see when the light is on. Just the same results as with the hrw pigtail though. With the spade connectors plugged in as Type 1 (shown on the Owner's Club website) almost works but the relay buzzes and doesn't hold closed, resulting in low volts on the hrw and a little radio interference too. Plugged in as Type 2 (from this website) it blows the 10A fuse in the boot - again.

Yes, I agree the wiring doesn't seem to be as it should, and I'm looking for help as to what might be wrong. I suspect a poor earth somewhere, which might explain the relay not getting enough volts to hold in the closed position. I'm about to try tracing it all through for continuity, now it's daylight.

It's a rocker switch on this car and I suspect that may be where the poor contact is.

Any ideas why there seems to be two different pigtail connections? I thought there was only one Mk.1 OEM pigtail, but these two websites advise completely incompatible connections.

[Ken1958]

This might be of interest....

viewtopic.php?f=114&t=6684
M-m

Not really. As the 4th last Mk1 ever imported into the UK, this has all of the fittings and wiring for the hard top already installed. It should just plug and play... if it was a Mk.1 top.

[Mazda Mender]

It shows everything if you go further down for the correct plugs and sockets ,switchs also...etc
Regardless of how many cars you have imported ? It makes no difference to the issue...i have imported 100's in my time...most have different issues to sort from fat fingers haveing a mess...

Check the earths as you say....dash for the switch...under
The back deck panel for the socket and boot for the relay.
M-m

[Ken1958]

It shows everything if you go further down for the correct plugs and sockets ,switchs also...etc
Regardless of how many cars you have imported ? It makes no difference to the issue...i have imported 100's in my time...most have different issues to sort from fat fingers haveing a mess...

Check the earths as you say....dash for the switch...under
The back deck panel for the socket and boot for the relay.
M-m

I did look all the way to the bottom of the post, but there isn't anything there about how the wiring SHOULD be pre-installed. Since that seems to be the issue, it doesn't help.
As I said in the first posting, I have installed the switch, the fuse and the relay.
What difference does it make how many cars I have imported? The reason for asking here was to get some help from people that had more experience of these types of problem.

[Ken1958]

Yes, I agree the wiring doesn't seem to be as it should, and I'm looking for help as to what might be wrong. I suspect a poor earth somewhere, which might explain the relay not getting enough volts to hold in the closed position. I'm about to try tracing it all through for continuity, now it's daylight.

Checking the wiring continuity was a bit inconsistent, and I went through it a couple of times with slightly different results. I finally tracked the problem down to one end of the relay coil, more by luck than judgement. I don't know if it was just a broken wire or a corroded one, but it came off in my hand while I was moving the relay socket about. The copper was obviously brown from oxidation but it didn't look especially corroded compared to the others. After fiddling around to get the old connector out of the relay socket, I stripped the wire back to shiny new copper, soldered that to the connector, pushed it back into the relay socket and refitted the yellow retaining cap. I wasn't entirely convinced I had changed anything as, at that stage, I just thought I had fixed something that I had broken while diagnosing the problem. However, when I plugged in the relay and tried again, everything worked exactly as it should.

Not only did my test pigtail light correctly when plugged in as Type 1, but the relay doesn't buzz anymore, the radio interference has stopped and the heated window comes on correctly when that is plugged in.

I guess the buzzing was down to mechanical movement of the relay clicking closed being enough to disconnect the corroded/broken wire to the coil, which opened the relay, reconnecting the wire and hence oscillating on and off at the switch resonance. Strange that moving the relay about didn't affect that, but it would explain the low 8 volts initially measured at the window itself - it is now getting full battery volts when switched on.

Just in time for the colder winter days and nights.

[Mazda Mender]

Result , i knew it would be something silly, there is not really much to the circuit , thats why i said also check the switches, plugs,relays and sockets, just in time for the crappy weather... glad your sorted.
I had a cracker dropped off here on Saturday Mk 1 NA monza UK, intermittent charging, popping fuses,no side lights or panel lights, no indicators but she had hazards and no gauges working but the speedo because it's mechanical, a day stripping down and a day searching for each fault, one of which was a c*ck up piece of loom someone had made for the HRW with thin nasty speaker wire that had been ripped off and left to connect to the tub, there were more, but this one got to me the most..

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M-m

[Ken1958]

Result , i knew it would be something silly, there is not really much to the circuit , thats why i said also check the switches, plugs,relays and sockets, just in time for the crappy weather... glad your sorted.
I had a cracker dropped off here on Saturday Mk 1 NA monza UK, intermittent charging, popping fuses,no side lights or panel lights, no indicators but she had hazards and no gauges working but the speedo because it's mechanical, a day stripping down and a day searching for each fault, one of which was a c*ck up piece of loom someone had made for the HRW with thin nasty speaker wire that had been ripped off and left to connect to the tub, there were more, but this one got to me the most..

M-m

During my diagnostic efforts I measured the window heater resistance and its about 2.5 ohms, so its going to draw about 5 - 6A from the battery when first switched on. That must be getting close to the limit for cheap speaker wire. No wonder that segment looks frayed in the 3rd photo, it looks like the insulation has melted! I expect there was a nasty smell of burning plastic at some point when the HRW was used. With the wiring loom running past the fuel filler pipe, its amazing the car and owner survived long enough to bring it in! Hot wires and fuel vapour don't tend to hang around for long.