Frustrating instrument cluster problems (1 Viewer)

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Oct 11, 2020
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Hello guys

Before I start I have to confess that I am by no means knowledgeable when it comes to all things electricory so it could be that I'm just missing something obvious and, if so, sorry for wasting your time but here goes....

I have a rather frustrating problem with my 71' 40 series that I'm busy restoring. When I got the cruiser it came with 2 instrument clusters pictured here below:

IMG-20220818-WA0004.jpg


(12 volt system)

Now the problem is that both of these clusters are grounding out on the following pins on the barrel connector and thus also grounding out those circuits, which I'm pretty sure they shouldn't be doing:

Pin 1: ground (good)
Pin 6: high beam indicator light - headlight dimmer switch
Pin 8: turn signal indicator light RH - turn signal switch
Pin 9: turn signal indicator light LH -turn signal switch
Pin 10: to meter pilot light - light switch

IMG-20220818-WA0003.jpg


Now I have removed the loom (original) from the cruiser and stripped and traced it to see if there were shorts from these circuits to the black and white ground wire somewhere but there is not. The only time they come into contact is when the barrel connector is plugged into the clusters. When it's plugged in I get continuity between the #1 ground pin and the positive wires on those lighting circuits..

Furthermore even with the loom barrel connector unplugged from the clusters still I get continuity from the #1 ground pin to all the other pins mentioned above so it's definitely something going on with the clusters BUT the twist is that it only happens when all the small light bulbs are plugged into the cluster, these being the indicator bulbs, pilot light bulbs and the high beam indicator bulb.

What is going on? I am completely stumped and the only thing I can think of is that both of these clusters are damaged, one was apparently new. All the bulbs still work when I bench test them individually.

Can anyone tell me if I'm being a half wit or are the clusters cactus?

Thanks
 
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Sounds to me like you either have bad bulbs, or your bulb holders are the wrong ones and are shorting out
 
Joined
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The bulbs definitely ground the positive side contact of the bulb holder on the clusters when they are plugged in because I get continuity between the positive and negative terminals when the bulbs are plugged in and not when they are removed but yet they still work fine on the bench. Very strange.

I'm considering trying to removing the black and white ground wire from the #1 barrel connector pin and rather ground the cluster to the chassis via one of its screws and the screws used to keep it in the dash. That might remove the problem of grounding across the other pins. Or is that a bad idea? I just don'tike it because it's not the way it's supposed to work.

IMG-20220818-WA0005.jpeg


IMG-20220818-WA0011.jpeg


IMG-20220818-WA0013.jpeg
 

ToyotaMatt

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The bulbs definitely ground the positive side contact of the bulb holder on the clusters when they are plugged in because I get continuity between the positive and negative terminals when the bulbs are plugged in and not when they are removed but yet they still work fine on the bench. Very strange.

I'm considering trying to removing the black and white ground wire from the #1 barrel connector pin and rather ground the cluster to the chassis via one of its screws and the screws used to keep it in the dash. That might remove the problem of grounding across the other pins. Or is that a bad idea? I just don'tike it because it's not the way it's supposed to work.

View attachment 3090023

View attachment 3090024

View attachment 3090025




i know exactly what your issue is , what caused it , and how it happend as well ........

- i suggest you grab a at least 2 beers now because the facts here are going to be painful :confused:


- the old cluster was a retrofit for a 1971 , its newer like from 74-78 era , its got a 30 AMPS meter in it , i see the broken speedo cable still partly attached , to the ceramic speedo head attachment cylinder that stick out the back side middle

- also , oddly it has a AUTO-METER OLD skool repair and service yellow tags on it , i have seen this only one other time in my life .... that's interesting for sure and not a bad thing stand alone ,..............maybe ?

- now , the GRIM-REAPER part here :

- the newer cluster meter is a NON-USA KPH Kilometers unit , your old one there is a MPH mile per hour USA spec. only type ,


- they share some similar things , but differ also on some , but 1 MAJOR thing is the AMP meters

- MPH old one has a 30 AMPS meter gauge


- your newer one HAD a 50 AMPS meter Gauge originally , but now its missing and somebody removed it .......


- so , you might know about this perhaps , but you do not mention it above , at all ?

- or , you don't know about it , either way these are the hard core facts i can conclude only by examining your various TECH. photos above ...



- the ONLY possible reason anybody would take the time to PRY off the Silver PEWTER face plate to REMOVE the original 50 AMPS meter gauge ,

is because a person took a 12/78- and OLDER Land Cruiser COWL wire harness section , and actually removed both the LARGE 10 GAUGE SOLID white wire , and its partner in crime , the Large white wire w/ a blue tracer stripe .... BOTH have ring terminals on the ends to be clear ........

- a indeed attached them to the similar but ABSOLUTLY NOT the same in kind looking 2 HEX NUTS in the same location on the newer cluster , labled AMP METER on your Orange HAYNES Manual pages you show in your photos above ,



- you will notice the BLUE printed circuitry boards differ in shape , in a major way in the lower LH corner looking from the back side , that's because .............



- the newer cluster 50A amps meter , is not actually a AMPS meter al all in any way shape or form , its a simple 12v VOLTS METER ........

- for reasons i can't explain or know Toyota never changes the WORD AMPS to VOLTS in 1/79-10/85 Later cluster meters ?


- this fact still puzzles me to this day , but its a concrete fact never the less , ...........



- IF the battery was still connected when who ever decided to play car mechanic here , attached the 2nd of the 2 ring terminals , assuming the first one is already been attached ........

- the new cluster literally blew up and melted down in there hands then and there instantly ,

- if they had a clue , there battery was disconnected , they installed both ring terminals to the new cluster , secured it back to the dash via the 2 Philips head screws


- then or later at the very moment they re-hooked up the battery again , the instant BLOW up inside and subsequent meltdown will have occurred ,

both inside and various aspects of the blue printed circuitry as well without question .......

- this is why your getting the 100% ground signal or at every barrel connector PIN your testing , because its all fused together now from the melt down occurring



- see the large gauges whit and white/ w blue tracer stripe wires with ring terminals are FULL on B+ Batter Voltage and AMPS directly from it to the alternator ...


- NOTHING , not a single thing attaches to the 2 newer hex nuts on the lower left hand side corner where your once new 50 AMPS meter , or 12V Volts gauge once

lived in peace , died a tragic fate for sure .............

- .that poor little YAZAKI Meter was burned alive before it had a chance to see life and some 12v electricity properly flow through it .....:(


- i have seen this play out more then a few times over the years , so those are the facts




matt



( 0 ).jpg




@brian


 
Last edited:
Joined
Oct 11, 2020
Messages
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Location
Botswana
Hi Matt

Thanks for your explanation i see now that I was set up to fail with these 2 before I even began ! 2x beers on the way.....

You are right in that someone did remove the white and blue and white wires from the loom and replaced them with a red wire of the same guage, clearly there has been some foul play on the loom at some stage although they still seem to follow the original wiring diagram for that power circuit. All the other circuit wires are original as far as I can see except for the those aforementioned 2 white ones.

I bought it off the last owner as an unfinished project and he said that he wasn't sure if the clusters worked or not but assumed that the "new" one was fine. Apparently not.

Better start saving for a replacement cluster and I will take great care not to repeat the events you have explained above.

Just out of curiosity does this mean that all the guages are dead too or will they still be alright? Presumably I could at least get those to work temporarily by isolating them from the cluster circuitry and wiring them independently by taking power from somewhere else in the ignition and running new wires to the sender's?
 
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i know exactly what your issue is , what caused it , and how it happend as well ........

- i suggest you grab a at least 2 beers now because the facts here are going to be painful :confused:


- the old cluster was a retrofit for a 1971 , its newer like from 74-78 era , its got a 30 AMPS meter in it , i see the broken speedo cable still partly attached , to the ceramic speedo head attachment cylinder that stick out the back side middle

- also , oddly it has a AUTO-METER OLD skool repair and service yellow tags on it , i have seen this only one other time in my life .... that's interesting for sure and not a bad thing stand alone ,..............maybe ?

- now , the GRIM-REAPER part here :

- the newer cluster meter is a NON-USA KPH Kilometers unit , your old one there is a MPH mile per hour USA spec. only type ,


- they share some similar things , but differ also on some , but 1 MAJOR thing is the AMP meters

- MPH old one has a 30 AMPS meter gauge


- your newer one HAD a 50 AMPS meter Gauge originally , but now its missing and somebody removed it .......


- so , you might know about this perhaps , but you do not mention it above , at all ?

- or , you don't know about it , either way these are the hard core facts i can conclude only by examining your various TECH. photos above ...



- the ONLY possible reason anybody would take the time to PRY off the Silver PEWTER face plate to REMOVE the original 50 AMPS meter gauge ,

is because a person took a 12/78- and OLDER Land Cruiser COWL wire harness section , and actually removed both the LARGE 10 GAUGE SOLID white wire , and its partner in crime , the Large white wire w/ a blue tracer stripe .... BOTH have ring terminals on the ends to be clear ........

- a indeed attached them to the similar but ABSOLUTLY NOT the same in kind looking 2 HEX NUTS in the same location on the newer cluster , labled AMP METER on your Orange HAYNES Manual pages you show in your photos above ,



- you will notice the BLUE printed circuitry boards differ in shape , in a major way in the lower LH corner looking from the back side , that's because .............



- the newer cluster 50A amps meter , is not actually a AMPS meter al all in any way shape or form , its a simple 12v VOLTS METER ........

- for reasons i can't explain or know Toyota never changes the WORD AMPS to VOLTS in 1/79-10/85 Later cluster meters ?


- this fact still puzzles me to this day , but its a concrete fact never the less , ...........



- IF the battery was still connected when who ever decided to play car mechanic here , attached the 2nd of the 2 ring terminals , assuming the first one is already been attached ........

- the new cluster literally blew up and melted down in there hands then and there instantly ,

- if they had a clue , there battery was disconnected , they installed both ring terminals to the new cluster , secured it back to the dash via the 2 Philips head screws


- then or later at the very moment they re-hooked up the battery again , the instant BLOW up inside and subsequent meltdown will have occurred ,

both inside and various aspects of the blue printed circuitry as well without question .......

- this is why your getting the 100% ground signal or at every barrel connector PIN your testing , because its all fused together now from the melt down occurring



- see the large gauges whit and white/ w blue tracer stripe wires with ring terminals are FULL on B+ Batter Voltage and AMPS directly from it to the alternator ...


- NOTHING , not a single thing attaches to the 2 newer hex nuts on the lower left hand side corner where your once new 50 AMPS meter , or 12V Volts gauge once

lived in peace , died a tragic fate for sure .............

- .that poor little YAZAKI Meter was burned alive before it had a chance to see life and some 12v electricity properly flow through it .....:(


- i have seen this play out more then a few times over the years , so those are the facts




matt







@brian
Great instrument cluster tech writeup Matt.
 

Coolerman

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Now Matt, you know that Toyota is correct labeling the 50A Amp Meter an Amp meter, because that is exactly what the meter does! It indicates AMPS not volts.
It's HOW if does this that leads to the confusion.

Yes the meter itself is technically a volt meter. It measures the voltage drop across the fusible link to determine how much current is flowing through it and displays that as AMPS. It does this very poorly BTW. The OEM fusible link itself is only 4 " long and therefore has a very low resistance, the voltage drop across it is quite small even when 50 amps are pulled through it. That is why the 50A Amp Meter is not very sensitive to small changes in current flow through the fusible link. The meter they chose is simply not sensitive enough to measure the small voltage drop.

Totally off topic: I have set up a 100A shunt (a shunt is a calibrated strip of metal with a known resistance) in place of a fusible link on later harnesses, (or the Amp Meter on early harnesses). Using my Fluke 87 meter to measure the voltage drop across the shunt, I can easily detect current flows below 1 amp something the Toyota Amp Meter cannot do...
 
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At the risk of angering the purists what If I take the barrel plug off the cluster leave it off do you think it would be possible to get the gauges to work temporarily by isolating them from the cluster circuitry and then wire them independently by taking power from somewhere else in the ignition and running it to the gauges and then new wires to the sender's?

Which pole on the fuel gauge, oil pressure gauge and temp gauge are for power input and which would go to the sender? All the guages look fine still.

This would just be a temporary solution obviously until I can buy a new cluster.
 

Coolerman

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You are going to have a bunch of issues here. First the gauge cluster MUST match the sensors. By that I mean if you have a 1971 truck with 1971 sensors for the wtaer temp and oil pressure you MUST use the 1971 gauge cluster. If you want to use the later gauge cluster you have, you MUST use the later sensors or the gauges simply will not read correctly. So first determine which sensors you have then go from there. I personally would highly recommend just sourcing the correct gauge cluster for your 1971. Hopefully the wiring is not too hacked up to enable you to just plug it back up.

Here is the thread where you can read all about the issue with the gauge cluster matching the sensors: Gauge Cluster Thread
 
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Thanks for the help and information guys, I really appreciate it. I will endeavour to get a new cluster and matching sensors before I take this any further. Do it right, do it once.
 

JVZii

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I can't help but to throw in as well. I am guessing that you have updated the transmission as a 71 would have a screw in speedometer cable and smaller gauges Like this one. Note the turn signals are not on the cluster for this year.

IMG_20220212_191220.jpg
IMG_20220212_191242.jpg


If your PO had gotten half way through a retrofit it may be easier to get a 73 cluster. It is a one year only cluster that has the updated gauges and speedometer but no circuit board on the back. This would allow you to make your own harness without working around a circuit board. You still need to figure out the sending units.

IMG_20210326_151433.jpg

IMG_20210326_153744.jpg


Or you can back to original gauges (no sensor work needed)

I have all of this gear if your interested. And I take old clusters as payment.
 
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Thanks for the offers for help with the cluster repairs guys, much appreciated. Unfortunately I am in South Africa so its not practical. I can get a new cluster here, it's just getting the corresponding sensors that will require some more research.
 

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