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Temperature gauge malfunction

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635sharknose
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Temperature gauge malfunction

Post by 635sharknose » Fri Mar 13, 2020 8:13 pm

After reinstalling my dashboard my temperature dash gauge no longer works.
Everything works except this gauge.
The gauge worked fine before removing the dashboard.

Anyone have an idea what the cause might be?
Thanks for the help.
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1987 635CSi Bronzitbeige
www.bmwe24.nl

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jps635
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Re: Temperature gauge malfunction

Post by jps635 » Sat Mar 14, 2020 7:43 am

Most likely a connection or board fault but depends what you did while the dash was out. Check the 7.5 amp fuses and retrace your steps
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plip1953
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Re: Temperature gauge malfunction

Post by plip1953 » Sat Mar 14, 2020 8:35 pm

If all else fails, I have a spare dash for a late model car and you could maybe try that to either rule in or rule out the fault being with the gauge.
Phil
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635sharknose
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Re: Temperature gauge malfunction

Post by 635sharknose » Sun Mar 15, 2020 6:35 pm

Thanks for the tip, I will take out the cluster soon to investigate. Checked the fuses, all fine.

Thank you for that offer Phil! I will do my best to locate it and keep your offer in mind if I can't find it.
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www.bmwe24.nl

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Re: Temperature gauge malfunction

Post by 635sharknose » Sat Mar 21, 2020 4:14 pm

Today I tried to fix the problem but so far without luck.
I opened the cluster and looked for bad solder or bad connections. I have not noticed anything bad.
I noticed that the pins of the gauge PCB mounted on the mainboard were oxidized, so I sanded and cleaned the pins with a brush with contact spray.

Image

I also connected both contacts of the temperature sensor to the mass of the car to see if the gauge would function. The warning light however does work properly.

Image
Image

I have checked all cables in the dashboard, everything looks neat, no damage and no dirt and all connected.

Anyone have an idea? Does anybody perhaps notice something by looking at the pictures below?

Image
Image
Image
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baders
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Re: Temperature gauge malfunction

Post by baders » Sun Mar 22, 2020 5:38 am

You need to go about this in a systematic fashion. Do you have the appropriate Electrical Troubleshooting Manual from here ?

http://wedophones.com/Manuals/BMW/

Do you have a digital multimeter ?

One of the pins on the sender is a switch contact (activates the idiot light on dash). The other pin on the sender is the output from a heat dependent varistor (operates the gauge).

1) Pull out the coolant temperature sender. Pop it in hot water and read the resistance change. Replace if required.
2) Check continuity of the wire (should be brown/violet) back to pin 4 on the C101 connector plug.
3) If good Check continuity of the wire (should be brown/red) further back to pin 12 on the C1 connector plug.
4) As you have a temperature warning idiot light on the dash, I'm thinking you might have an earlier 1987 model ? The temperature gauge also relies on the service interval processor so there may be a problem with that. To check this run a wire from the pin 1 on the C6 plug to pin 12 on the C1 connector plug and see if it works.
5) I have made up a "resistance box" with multiple variable resistors (pots) of different ranges and can use this to simulate all senders. You might want to think of building one.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
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Ralph in Socal
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Re: Temperature gauge malfunction

Post by Ralph in Socal » Sun Mar 22, 2020 6:57 am

Only thing I would do different from Baders post is to leave the sensor in place and check your resistance value as you let the engine get hot. Paul knows what he's talking about!!! I didn’t even know the word varistor existed!! Variable resistor - makes sense

Check resistance between the contact and a ground point on the engine, not the body of the sensor as this will also test the sensor being properly grounded. The idiot light working does indicate it is properly grounded though. Since the temp gauge worked before I would focus on wire continuity. Good luck

Ralph
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635sharknose
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Re: Temperature gauge malfunction

Post by 635sharknose » Sun Mar 22, 2020 1:05 pm

Thanks for the info and assistance guys!! =D>

I did some tests again today, below my findings.
Hope you guys can think of something to solve this issue.

1) Pull out the coolant temperature sender. Pop it in hot water and read the resistance change. Replace if required.
I did Ralph's way, drove a lap to warm up the engine.
I measured the difference in resistance with a cold motor and a warm motor, the sensor seems to function properly.

Cold.JPG
Cold.JPG (136.5 KiB) Viewed 1094 times
Warm.jpg
Warm.jpg (90.66 KiB) Viewed 1094 times

2) Check continuity of the wire (should be brown/violet) back to pin 4 of plug C101.
Measured, these are connected.

3) If good Check continuity of the wire (should be brown/red) further back to pin 12 on plug C1.
Measured, are also connected, there is a closed circuit between pin 4 of plug C101, pin 12 of plug C1 and the plug on the temperature sensor.

C1.JPG
C1.JPG (77.08 KiB) Viewed 1094 times

4) As you have a temperature warning idiot light on the dash, I'm thinking you might have an earlier 1987 model ? The temperature gauge also relies on the service interval processor so there may be a problem with that. To check this run a wire from the pin 1 on the C6 plug to pin 12 on the C1 connector plug and see if it works.
My car was built in mid 1986 and delivered in January 1987.
I see in the diagram that the signal indeed goes through the service indicator, do you know why?
I assume plug C6 are the pins soldered on the PCB (see photo below)? In the diagram I see a frame drawn around the cluster and this connector falls within the frame, meaning the connector is inside the cluster. The only connector I can imagine to be C6 are the 12 soldered pins. I think the only way to connect these is to solder a bypass on the PCB, from the soldering socket of pin 12 of plug C1 to the soldering socket of pin 1 of plug C6. Or do you have a better way to make a bypass?
I cannot find a layout of the C6 plug, so I cannot determine which pin is actually 1.

C6 plug.jpg
C6 plug.jpg (98.27 KiB) Viewed 1094 times

5) I have made up a "resistance box" with multiple variable resistors (pots) of different ranges and can use this to simulate all senders. You might want to think of building one.
Oh, that's interesting, how did you make this? And for was purposes can you use it?

Thanks for the help guys!!!
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Re: Temperature gauge malfunction

Post by baders » Tue Mar 24, 2020 2:40 am

Sorry about the late reply, bit going on here ! :)
I see in the diagram that the signal indeed goes through the service indicator, do you know why?
I believe the service indicator takes into account an aggregate of engine temperature to calculate service intervals.
I assume plug C6 are the pins soldered on the PCB (see photo below)?
Yes that is the case.You will just have to find the best way to bridge a wire to ideally the ground (G) terminal on the instrument cluster (temp gauge). Not sure how you would do that but if you have the cluster apart it may become apparent.
Oh, that's interesting, how did you make this? And for was purposes can you use it?
I bought a series of potentiometers from my electronics store in differing ranges and mounted them in a box with terminals. Have a look in my LOCUTUS thread for images.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement

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635sharknose
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Re: Temperature gauge malfunction

Post by 635sharknose » Tue Mar 24, 2020 3:54 pm

Thanks for your reply and help! =D>
As I'm sure now it is within the cluster, I am thinking of sending it to a repair shop for a decent repair.
I am afraid to damage it when trying to bridge.

Found your resistor box, what a good idea!
Googled a bit around and found this one, not variable but quite some ranges, which I think will be useful too.

Image

Thanks again for the help, really appreciate it! You guys have brought me much further in the research! =D> =D> \:D/
Instagram: @635sharknose
1987 635CSi Bronzitbeige
www.bmwe24.nl

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Re: Temperature gauge malfunction

Post by emac » Tue Mar 24, 2020 9:52 pm

I am just throwing this out there. I vaguely recall on an old 3 series that I owned had problems with SI board or batteries and caused the temp gauge to do crazy stuff.

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Re: Temperature gauge malfunction

Post by 635sharknose » Tue Mar 24, 2020 9:59 pm

Do you think the batteries can have influence on the behaviour of the temperature gauge?
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Re: Temperature gauge malfunction

Post by emac » Wed Mar 25, 2020 12:23 am

I think it would happen on the e30. I just dont have a lot of experience with the e24.....yet!

Is the SI board plugged in properly?

https://www.pelicanparts.com/BMW/techar ... teries.htm

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Re: Temperature gauge malfunction

Post by emac » Wed Mar 25, 2020 12:42 am

another article about SI and gauges

http://bavrest.com/technical-articles/bmw-e30-si-board

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635sharknose
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Re: Temperature gauge malfunction

Post by 635sharknose » Wed Mar 25, 2020 5:50 pm

Thanks! Interesting links. :D
This looks identical in the E24 as in the E30.
I do read that normaly mutliple things stop working (oil/ led's/ temp).
Will take out the cluster again and check the batteries.
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Re: Temperature gauge malfunction

Post by 635sharknose » Sat Mar 28, 2020 11:30 am

Today I disassembled the cockpit again completely.
Batteries measured, although they have 11-1989 printed on them, they were neatly 3v and were not leaking. All good here.

Then sanded all contacts, pins and cleaned them and the sockets with a brush with contact spray.

Put everything back together and... it works again! :-({|= \:D/

Thanks for the help guys, appreciate it.
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cluster.jpg
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Instagram: @635sharknose
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emac
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Re: Temperature gauge malfunction

Post by emac » Sat Mar 28, 2020 9:00 pm

Great! So it was most likely a bad connection.

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Re: Temperature gauge malfunction

Post by baders » Sun Mar 29, 2020 3:12 am

A good result, though I would be replacing those 1989 SI batteries !
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement

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Re: Temperature gauge malfunction

Post by plip1953 » Sun Mar 29, 2020 8:08 am

baders wrote:
Sun Mar 29, 2020 3:12 am
A good result, though I would be replacing those 1989 SI batteries !
Even if the old ones are still chucking out a good voltage? Is there a risk of them splitting open or similar with being so old?

I'm pretty sure the ones in my '88 Highline are originals!

Do the batteries only recharge with the engine running or are they always being charged as long as the main battery is connected?
Phil
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baders
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Re: Temperature gauge malfunction

Post by baders » Mon Mar 30, 2020 1:58 am

There have been cases where old batteries have split and damaged the circuit boards so why not replace if you are in there ? I re-engineered mine by installing a battery holder to enable ease of replacement in the future.

The service interval processor memory power supply is "hot at all times" therefore the engine does not need to be running.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement

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