Temp sensors issue after rocker gasket change m20b23

[Alyman]

Hi

So, following up on my last post, I completed putting things back together after changing the rocker gasket... well, I think I did....

I'd figured I'd give the rocker cover a quick refurb while it was off, and while removing it I made a mental note of which connection points would benefit from sanding back to bare metal after painting to ensure that any electrical connections would continue to work. I'm convinced that there were three studs which had a wire going to them - circled below:

rocker.png

When reassembling, the connections to the two points circled in green were fine - but bizarrely there is no obvious connector to go back on the point circled in red (up next to the temp sensors). I got to the point of second guessing myself as to whether there was something on there or not. I even took the rocker cover back off again to make sure that there wasn't a wire that had come loose and somehow fallen in there. Nothing under the car either.

I'd decided that I must have just misremembered, so tried starting the car - but it's clear that something is up. The temp gauge no longer functions, and the idle is much lower/rougher than before (which I'm assuming is due to there being no temp data?).

So the question is: is there supposed to be something to connected to that stud I've circled in red? If so, does it relate to the temp sensors?

[flybynite]

How old is your 323i? My 323i is not close enough to me to look at but I don't recall having so many connections to the cam cover studs. Certainly not the big earth strap but it may be a different build date and ther were many changes.

All the temp sensors are around that (red) area, I would check the plugs are seated correctly and then start checking continuity.

Have you checked fuses?

[Alyman]

Thanks for the reply

Build date shows up on a VIN decoder as 1985-01-03 (I'm unsure if that date format means 1st March or 3rd Jan though!).

I've tried disconnecting the wires going to the two sensors, cleaned up the connectors and pushed them back on, so hopefully they are seated correctly. I do own a multimeter somewhere but admit to not having a clue how to check continuity - would defo give it a shot if there's a basic script I could follow?

I haven't checked fuses (must admit I hadn't thought they'd be a suspect in this scenario) - which would you recommend checking?

[flybynite]

Yours is a couple of years newer than mine which would explain the difference, not many 323is left now so hard to find a match.

Try fuse number 9, engine electrics. But to be safe I would check them all. You don't have to take them out, just put the multimeter points into the top of the fuse.

Have a read of these to give you an idea.

https://www.e30zone.net/e30wiki/index.p ... ot_Working

[Alyman]

OK - all fuses check out fine with the multimeter. Have read through the link posted and am trying to follow the troubleshooting notes.

My c101 is slightly different to the diagram posted in the C101 wiki page - I have 19 pins rather than the 17 on the diagram - and although the general concept of there being a 'grid' of nine pins to the left (looking from the back) and a grid of six on the right is still recognisable as the pattern, many of the wire colours don't seem to match the descriptions on that page.

c101.JPG

Having said that, I do have a brown wire at pin 4.

Can I just confirm if I'm setting up this test correctly?

With a probe in pin 4, and the other free, I have a reading of 1 (which makes sense I guess). When I touch the other probe to the bonnet latch mechanism (is that suitable for grounding?) I get a high reading > 1000. Is this the correct condition for the test to take place? i.e., if I turn the ignition to the 'on' position now, the temp gauge should hit max?

[Alyman]

Also, for the benefit of anyone searching this topic later, I've found a different diagram of the c101 which more closely matches my car (I just seem to have a couple of extra wires - locations 2 and 15):

C101 1985 325e.jpg

[Alyman]

So, having hopefully done the test correctly (short length of wire between pin 4 and a tower strut nut) the result is that the gauge doesn't move. Which I guess means there's trouble somewhere between the c101 and the gauge.

I don't think the brass nut on the back of the cluster will be the issue - the gauge was working immediately before changing the rocker gasket (and I already had the instrument cluster out recently to tighten the nut for the fuel gauge - I made sure that the nut for the temp gauge was OK while I was there).

So I guess this means that I've disturbed something in the main section of loom that runs along the top of the bulkhead? Obviously, I did have to detach that from its mounting point on the rocker and shift it about a bit during removal and refitting of the cover.

Any ideas for what my next step should be - is there a way to narrow down the location of the issue any further ?

[BenHar]

Maybe the C191 plug?

https://www.e30zone.net/e30wiki/index.php?title=Loom

Ben

[Alyman]

My thinking was that the route from the sensors to gauge went like:

Temp sensors linked to C191 >
C191 links to C101 >
C101 links to the gauge

So I guess my understanding was that the 'pin 4 test' indicated that the issue was somewhere between the c101 and the gauge. Am I off the mark on that? I could be totally wrong - I'm new to this electrical troubleshooting stuff

The other question I have is whether the brown sensor exclusively drives the gauge, or is it also sending the signal to the engine mgmt? The rough idle makes me think that it's not just the gauge that's that not getting the reading, but also the mgmt as well (assuming it's using temp data to do its job). Is there another test related to checking the signal the mgmt uses (if it's separate from the signal from the brown sensor)?