Club 80-90 Forums

jswaggers,

Yes I am using a multi meter to fault find, are there other tests I can do?

You could test for continuity from....... the terminal on the clock exposed by....... 'removing the white plastic sheath that connects to the track that goes to pin 5'........and the end of the track 5 itself, if you have not already done that.
The copper tracks themselves tend to break close to the point where they enter the multipin socket on the loom. (Great design isn't it?) Several of mine have been repaired with a bit of wire soldered in place, to complete the circuit.

Can you explain...

So now I have two working temp gauges and one working clock I have one complete set of working instruments (they work on the bench),

How are you applying the + and - voltages........via the ends of the tracks or direct to the clock and gauge terminals. Just trying to see whether the PCB tracks are intact.

Mike

Odd that both Instrument clusters have exactly the same problem but since you have tested both on a bench and the clock/guage work then, as Grun says, you need to check the continuity of the pcb membrane tracks and eliminate that as a possible cause. The track can develop a hairline crack where the membrane cover stops to allow the multipin connector to come into contact with the exposed copper track, it also bends at this point. You won't see the crack if it exists, believe me! Also, though the temp sender wire connects to Pin 6 you will see that there doesn't appear to ba track at pin6. The trackat pin 6 runs behind the membran panel and routes to pin 4 of the multipin connector. So you have the possibilty of a hairline fracture - at PCB track 4 or a damaged section where it loops behind the folded edge of the pcb membrane at the connector itself.

You will need to remove the plastic connector shroud and perform continuity measurements:-

a) from Pin 6 to point C on the gauge

b) from pin5 to the +12V connection on the clock (note the small hole that exists in the PCB membrane where it folds over the +12 Terminal, place your probe in the hole to access the terminal or remove the plastic clip if you prefer)

The only common connection between the clock and the temp gauge is that both earth behind nut B (ref. photo earlier in the thread!) but since everything else functions I doubt there is a problem here.

Other problems have been reported such as Clutch fluid spilt onto the connector and damaging the tracks as well as the usual problem of the copper tarnishing and causing poor connections. If the PCB tests OK then we can proceed from there.

Grun wrote:jswaggers,

Yes I am using a multi meter to fault find, are there other tests I can do?

You could test for continuity from....... the terminal on the clock exposed by....... 'removing the white plastic sheath that connects to the track that goes to pin 5'........and the end of the track 5 itself, if you have not already done that.
The copper tracks themselves tend to break close to the point where they enter the multipin socket on the loom. (Great design isn't it?) Several of mine have been repaired with a bit of wire soldered in place, to complete the circuit.

Can you explain...

So now I have two working temp gauges and one working clock I have one complete set of working instruments (they work on the bench),

How are you applying the + and - voltages........via the ends of the tracks or direct to the clock and gauge terminals. Just trying to see whether the PCB tracks are intact.

Mike

I have been applying the voltages to the clock via pin 3 for -ve direct the clock for +ve.

I'll try the continuity tests, thanks

AngeloEvs wrote:Odd that both Instrument clusters have exactly the same problem but since you have tested both on a bench and the clock/guage work then, as Grun says, you need to check the continuity of the pcb membrane tracks and eliminate that as a possible cause. The track can develop a hairline crack where the membrane cover stops to allow the multipin connector to come into contact with the exposed copper track, it also bends at this point. You won't see the crack if it exists, believe me! Also, though the temp sender wire connects to Pin 6 you will see that there doesn't appear to ba track at pin6. The trackat pin 6 runs behind the membran panel and routes to pin 4 of the multipin connector. So you have the possibilty of a hairline fracture - at PCB track 4 or a damaged section where it loops behind the folded edge of the pcb membrane at the connector itself.

You will need to remove the plastic connector shroud and perform continuity measurements:-

a) from Pin 6 to point C on the gauge

b) from pin5 to the +12V connection on the clock (note the small hole that exists in the PCB membrane where it folds over the +12 Terminal, place your probe in the hole to access the terminal or remove the plastic clip if you prefer)

The only common connection between the clock and the temp gauge is that both earth behind nut B (ref. photo earlier in the thread!) but since everything else functions I doubt there is a problem here.

Other problems have been reported such as Clutch fluid spilt onto the connector and damaging the tracks as well as the usual problem of the copper tarnishing and causing poor connections. If the PCB tests OK then we can proceed from there.

Thanks for the post, I'll try the tests and report back.

Right I have done some continuity tests on the PCB of the set that has the working gauge and clock.

From point C on the previously posted photos to tracks 4 & 6 on the PCB there is continuity.

From track 5 to the point on the on the back of clock where the white sheath is there is continuity (as expected as this clock works when connected directly to 12v?)

Also as my assistant was available I did a continuity check on from the +ve (yellow & red wire) of the temperature sender to pin 6 on the multi plug and this was fine. Seeing as I had checked the -ve (brown wire) earlier on does this mean the wiring between sender and van can be ruled out?

Thanks again for your help.

jswagger,
I was hoping AngeloEvs would respond, as he has far more in depth knowledge and hands on experience than me.....but if 'twer me....

Why don't you put the assembly into the van and connect the multipin to the pcb.
The clock should run with the battery connected,(even with ignition off).
If not, check you have battery +ve on the clock terminal where the white sheath is.
If no +ve........ could be connection between multipin connector and PCB track, or further upstream,(fuse 3 ok?).

You have proved the wiring, (sender to earth and sender to multipin 6), to be sound. See if the temperature gauge shows signs of life when ignition switched on,(with sender connected perhaps run the engine to warm up). If no joy..... Ignition OFF, bridge the wiring connector at the sender with a bit of wire completing the circuit from the gauge to earth. This should move the temperature gauge to full/right scale, when Ignition is switched ON briefly.
This will prove the wiring, multipin to PCB connection, and gauge are good, leaving the sender or sender contacts as suspect. (sender contacts could be dirty).
Mike.

Thanks Grun,


As it happened I plugged the instrument set into the mulitplug last night and came out this morning and the clock is only working!

As for the temp gauge I ran the engine for 20 mins (till warm air came out of the heater) and no movement from the gauge, I take it it should have moved by then? (I have never seen a working one!) I did the shorting test you suggested and the needle moves when the ignition turns oon so the problem looks like it is the sender or plug? I'll leave the engine to cool down before having a look at that.

Nearly there

If you have confirmed that the continuity of the yellow/red from the coolant temp sender to instrument panel is OK and that shorting the yellow/red at the temp sender yo the engine block causes the temp gauge to work (ignition on), then:-

a) confirm that the brown wire at the temperature sender connects to earth (I use the engine block as an earth).

b) visually check the condition of the terminals at the sender.

c) measure the resistance of the sender itself (they do go open circuit) by placing the probes directly across the sender terminals.

Cold Engine anywhere between 2000 ohms and 1000 ohms

Hot engine approx 100 ohms

AngeloEvs wrote:If you have confirmed that the continuity of the yellow/red from the coolant temp sender to instrument panel is OK and that shorting the yellow/red at the temp sender yo the engine block causes the temp gauge to work (ignition on), then:-

a) confirm that the brown wire at the temperature sender connects to earth (I use the engine block as an earth).

b) visually check the condition of the terminals at the sender.

c) measure the resistance of the sender itself (they do go open circuit).

Cold Engine anywhere between 2000 ohms and 1000 ohms

Hot engine approx 100 ohms

I have already checked there is continuity between the brown wire (earth?) of the plug on the temp sender to the pin marked B on the photo so that circuit is fine?

Apologies for the dumb question but I haven't used the resistance setting on the multimeter before. Do I set it to the 2k setting and then just plug it into the round multi plug in the photo?
Thanks again.

Yep, set the meter to read 2K or close to that depending on your M/meter. I would run the engine for a few minutes just to get it warm and this will get the sender resistance within 1K -2K. If you don't want to crawl under the van then the measurement can be made from the junction box Connector in the engine bay. There are two multi pole connectors in there but only one has the red/yellow tem sender wiring and that is the one you need. Disconnect it, the female side (as shown in the picture with the pins) is where you measure the sender resistance. Visually check, red/yellow and brown, place meter across the femal pins and take the measurement.

Run the engine untill properly warmed up and repeat, resistance should fall dramatically to around 100 ohms or less.

Good news js,

AngelEvs has just beaten me to it with a similar reply to the one I was about to post.

Don't know if you can get at the sender to clean the contacts where the plug goes. If you need to change the sender, it is held in place by a plastic or metal clip, and just plugs in with an 'O' ring to seal it to the thermostat housing. Perhaps better to have a replacement with a new 'O'ring ready to plug straight in to keep coolant loss to a minimum.

I've tried to test the resistance using the round multiplug in the van and nothing happens (i.e. the screen just reads a 1 (and the 1 appears when I switch the multimeter to 2k). Perhaps this indicates a dirty connection on the temp sender plug? I will get under the van to check there too.

Out of interest if I do a continuity test across the two terminals of the temp sender itself and it fails does this mean the sender has failed open circuit?

Out of interest if I do a continuity test across the two terminals of the temp sender itself and it fails does this mean the sender has failed open circuit?

Yes, provided you have good contact, 1 on the meter is open circuit. If you short the two meter leads together with it set on 2000 ohms the display should read close to zero (001or 003 for instance) just proves the meter is functioning.

Mike

on my 1.9DG I have same prob - working LED but no gauge. Been over all the connections and all clean. Checked the resistance across the two pins given in T7 junction box (above pic) and nothing, no continuity either.

now move to one pin across (ie moving the blue pin in the picture one lower) an it reads about 20 ohms (set on 200 it reads 20.1 ish). so where does this leave me you reckon.. new sender unit? or measuring wrong maybe? 20 ohms is a false reading surely it should be all or nothing?


PS after five years of ownership and trying to figure these sorts of problems out (haynes is blx) i just discovered this forum... woo! thanks to all who post its well appreciated!!

zanzibaa,
You wrote.........

now move to one pin across (ie moving the blue pin in the picture one lower) an it reads about 20 ohms (set on 200 it reads 20.1 ish). so where does this leave me you reckon.. new sender unit? or measuring wrong maybe? 20 ohms is a false reading surely it should be all or nothing?

I am only working from the Haynes 'BLX' wiring diagram and AngeloEvs' photo and assuming that the pins are numbered from 1 clockwise you would be checking from earth to earth through the low pressure oil switch, if you have one meter probe in the socket one anticlockwise from the blue marker pin, and the other in the one with the black marker. I don't want to pull a working van to bits to check this myself, 'If it aint broke............

Best check is the meter directly across the sender pins themselves, and if you have good contact and a very low reading (close to zero ohms) then time for a new sender methinks, but do have a good read, AngeloEvs is the 'main man' having really researched this system and a search (top of page) will turn up all sorts of 'previous' on this fault.
Mike