New project 89

[rufrob]

I had a shop clean and test the cluster.
All the gauges pass the bench test. Upon reinstalling it only the temp gauge doesn’t move or work. All the other gauge work perfectly and rise with the ignition on. Only the temperature gauge doesn’t move at all which suggests the issue may be in the ignition circuit.
Ignition switch to relay, relay to cluster.
Any suggestions?
I also resealed the oil cooler, replaced windows scrapers, new wiper transmission link, used wiper motor because the old one only worked on 2 speeds. Next AC compressor and temp gauge.


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[Jfrahm]

Originally Posted by rufrob

All the other gauge work perfectly and rise with the ignition on. Only the temperature gauge doesn’t move at all which suggests the issue may be in the ignition circuit.
Ignition switch to relay, relay to cluster.

Why do you think that? I would think there would be one ignition-switch-to-cluster circuit and not a specific one for the temp gauge. I would check the circuit at the cardedge connector, if the cluster is OK then it has to be the connector or the circuit.

[rufrob]

I verified there its accessories power at connector A on the instrument cluster and power at connector 8 at the connector for the engine harness. Still the gauge is dead. What next?

Also the wiper goes down a bit when activated. It parks properly but I had the move the arms further up to stop them from going off the glass. What would cause the wiper park properly then move
a 1/4 inch down before moving up?


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[Jfrahm]

"I would check the circuit at the cardedge connector, if the cluster is OK then it has to be the connector or the circuit."

Backprobe the connection for the temp gauge at the cardedge connector and see if there is any continuity, try grounding it, ground through a resistor, etc.

Also ohm the circuit back towards the sensor with the connector disconnected.

[Monkey Wrench]

pul off your wiper arms, turn them a notch and reinstall.. If you want to look at the thing that makes them park int he right position its part of the wiper motor gearbox, open it up..
you can lube it and how it works is pretty self explanitory.. if you find bushings on the wiper arms maybe give them some lube.

If you take the motor apart check the magnets, they are bonded to the motor case, I've found them in a state where the motor ran but the magnets had come loose and were stuck to the armature, miraculously it ran slowly but there should be an air gap. the magnets dint go anywhere , they couldn't turn with the armature but the armature was all polished from them being stuck to it.. I cleaned and glued them back with JB weld and that fixed it..

i've had issues with the serrations wearing out then the wiper arm won't lock down properly and stay where it should, then the woper arms get out of position.. . I stuck it back with some JB weld, now a few years later, I'm trying to figure out how to get them off because I want to check the seal for my heater motor so I want to remove the grill which means removing them, and realized JB weld is good up to 600 dregrees so I' m not sure if I can unstick them by heating.. better to replace but I needed it for work,, maybe locktite is easier to break with heat. you can look if its been slipping about and if so, well that's another issue you may see..

I think what can happen is the wipers freeze in place then when switched on there is quite a bit of torque there and the blades can' t move , then the wiper arms can strip, especially if they are a bit loose to begin with.

i read the symptom again, if they go down before going up Id have a look at the gearbox near the motor. there is a micro switch there maybe its loose or similar. sometimes the whole mechanism can develop some slop too.

you can check with others to see if its hard to remove all that as an assembly , it muight be a but buried int he dash but otherwise its usually mainly just the wiper arms and maybe a couple bolts.. maybe its possible to change bushings and such to remove the slop if that is an issue.. I think there may be some bronze bushings in there that dry up and never get any more lube due to the location, on some cars you can access them from under the dash and pull out the whole contraption. The bushings may not be hard to replace if their holes go all egg shaped.

[rufrob]

Originally Posted by Monkey Wrench

pul off your wiper arms, turn them a notch and reinstall.. If you want to look at the thing that makes them park int he right position its part of the wiper motor gearbox, open it up..
you can lube it and how it works is pretty self explanitory.. if you find bushings on the wiper arms maybe give them some lube.

If you take the motor apart check the magnets, they are bonded to the motor case, I've found them in a state where the motor ran but the magnets had come loose and were stuck to the armature, miraculously it ran slowly but there should be an air gap. the magnets dint go anywhere , they couldn't turn with the armature but the armature was all polished from them being stuck to it.. I cleaned and glued them back with JB weld and that fixed it..

i've had issues with the serrations wearing out then the wiper arm won't lock down properly and stay where it should, then the woper arms get out of position.. . I stuck it back with some JB weld, now a few years later, I'm trying to figure out how to get them off because I want to check the seal for my heater motor so I want to remove the grill which means removing them, and realized JB weld is good up to 600 dregrees so I' m not sure if I can unstick them by heating.. better to replace but I needed it for work,, maybe locktite is easier to break with heat. you can look if its been slipping about and if so, well that's another issue you may see..

I think what can happen is the wipers freeze in place then when switched on there is quite a bit of torque there and the blades can' t move , then the wiper arms can strip, especially if they are a bit loose to begin with.

i read the symptom again, if they go down before going up Id have a look at the gearbox near the motor. there is a micro switch there maybe its loose or similar. sometimes the whole mechanism can develop some slop too.

you can check with others to see if its hard to remove all that as an assembly , it muight be a but buried int he dash but otherwise its usually mainly just the wiper arms and maybe a couple bolts.. maybe its possible to change bushings and such to remove the slop if that is an issue.. I think there may be some bronze bushings in there that dry up and never get any more lube due to the location, on some cars you can access them from under the dash and pull out the whole contraption. The bushings may not be hard to replace if their holes go all egg shaped.

Thank you so much for this detailed response. I pulled the original motor to find corroded brushes and I cracked the circuit board. I’ll have to be more careful this time when opening the transmission.


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[rufrob]

Originally Posted by Jfrahm

"I would check the circuit at the cardedge connector, if the cluster is OK then it has to be the connector or the circuit."

Backprobe the connection for the temp gauge at the cardedge connector and see if there is any continuity, try grounding it, ground through a resistor, etc.

Also ohm the circuit back towards the sensor with the connector disconnected.

Thanks. I will try that. But there is so little space to work back there.


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[Monkey Wrench]

Im kind of assuming but the temp sensor either changes resistance between its wires or maybe it changes resistance to ground. if its not too hard to remove you can put it in a pan of water, hook it to an ohm meter and watch the resistance change.. that way you should be able to see it changes as you heat a pan of water up.

if you know what the resistance range is and weather you have two wires with resistance between or one with resistance to ground , then you can always sub in some resistors and see what happens at the guage , maybe make sure the block is grounded, you can verify that with a jumper cable from the negative post to engine block. if the jumper cable changes anything with respect to the guage not working, you have a bad engine ground.

at home I have a little piece of kit called a resistance substitution box, you can make one up or there are commercially made ones, all it is, is a variety of resistors hooked to a multi position switch and all it does is makes switching between different resistors faster and easier.. you dont really need one but if you have a few resistors that are about within range you could sub the in to see if the problem is whith the gauge, if you do see the gauge react, then you might not need to go into the speedo unit's wiring.

if you had a spare sender in hand you can probably connect it to the wiring if you think you can access the wires and don' t want to remove it then just check it out of the cars engine block.. take a thermos of hot water to the car so you can immerse the thing in water of different temps while connected and not part of the engine.

it sounds like you found the wires as you are fiddling with the ribbon cable. you can check between there and the end of the wire for a break with both ends unhooked, measure resistance and check its not grounded by rubbing somewhere.

sometimes if I want to check continuity or check that I have the right wire in a bundle I just feed it 9V from a 9V battery at one end you could use a 1.5 volt too..

then go looking for the wire with 9V , no other wire will have 9V .. I just find it saves confusion.. then once you know you are on the right wire, you can check resistance and continuity and to see if it's either hot or grounded.. if both ends are disconnected then its not confused by some other current path.

sometimes I work on old antique electronics, modern resistors are pretty stable but old ones tend to drift up in value to higher resistance but they can go open too.. If they are all solderd to a circuit board then just placing a meter across it can be inaccurate because the board may provide some alternate current path, lowering resistance.. so its easy to know that is not the case if you un-solder one leg.. it is however impossible or some other alternate current path to RAISE the resistance..

If I put probes across a resistor that is in place and measure it and find more resistance than expected , in that case I know its a bad resistor.. because no alternate current path can raise the resistance.

If I measure the resistor and find it has less resistance than expected, that can be caused by an alternate path so unsoldering one end takes that ( alternate path ) scenario out of the equation.

most digital multimeters ( DMM"S ) do provide power via their internal 9V battery in order to read resistance in ohms. so if the circuit is sensitive electronics they may run on lower voltages so you can be a bit careful as to not provide ( 9V) power to any sensitive ( likely 5V) electronics inadvertently, when testing..

DMM's can load a circuit that is very sensitive to voltage, a scope or a vacuum tube voltmeter can usually test without loading the circuit.. most general car wiring is not very sensitive to things like that. I'd just be a bit careful if you go probing PCB boards, static shock can blow microchips too..

ribbon cables are notorious for having bad connections, they are generally ok if left alone but repeatedly plugging and unplugging may damage the microscopically thin copper traces on the mylar strip.. might not hurt to look with a magnifier or take a cell pic and expand it to see up close. a scratch across a trace can break continuity.
sometimes a DMM can come up with odd ( erroneous) readings, because it is so sensitive it can for example measure some odd voltage and display it, but that voltage may not have any appreciable current..

sometimes you can avoid that confusion by instead using an analog meter ( one with a needle) or even a battery or one of those cheapo car wiring probe testers that contains a battery. they are harder to be confused by.


Jfrahm is leading you on a good path, and he understands the particulars of 944 circuitry much better than I do. I hope my post didn't confuse things.

[rufrob]

Update. It got a new starter and I sent the gauge cluster out to a professional shop who said its fine so the coolant temp issue is somewhere in the harness.
Also just thinking of welding the springs on the static clutch to stop the rattle at spin down. Any ideas to solve the rattle?

[Monkey Wrench]

mine is an early 85 this car is I believe an 89 so I'm not sure if you may have a newer style clutch.

since I read about the rubber center clutches failing due to the rubber aging out. and also seeing pretty extreme pricing even just for the clutch friction plate itself. I have been wondering if there is an aftermarket alternative, especially one with springs instead of this rubber idea. I did find some friction material and it is possible to rebuild a clutch by riveting on new friction material , but that does nothing to help the rubber rot problems. I delt with a great shop that I had reline some brake shoes, and they could do clutch plates too, but I think they closed, probably because of asbestos issues.

I saw some time back where someone posted a pic of a clutch plate that looked like it was modified to use springs but I'm unsure which clutch it was. maybe it would be possible to re-use the center hub with the splines and marry that to a normal clutch?

it seemed to me that there are more alternative sources for the 16V cars than the older ones.

I tried a few vendors but did not find a good alternative . I spoke to a guy that had been installing V8's in Porsches, he said he does not ever use rubber centered clutches.

it would not surprise me if there is some other car with the same splines and a more normal clutch that would fit, but how to locate that info? I'm not sure how.. maybe if someone had access to a bunch of other clutches they could start to make such side by side comparisons.
Please let us know if you learn more.

[rufrob]

Thread revival.
Update. Turns out the used clutch disk I got was bad and the cause of the rattle. Interestingly Mazda FC RX7 uses the same clutch disk. Last Saturday it took 5 hours to get it all apart and I got the clutch assembly back in by evening. Sunday is when it all went to ***** when the reference sensor holder cracked and the transmission slipped off the floor jack and broke the ATF reservoir. Faaaaaaaaak. So today after work I got it all back together. I used JB Weld on the reference sensor holder and plastic weld on the reservoir. So I will let them set overnight and see if they work tomorrow. Even though the disks were the exact same size, I seated the TT in the pilot bearing and I torqued the PP to spec, the TT turned without the same level of resistance of turning the engine. I used a prybar on the torque converter. Really dont want to do this job again.
Also I replaced the fuel hoses in the engine bay with steel braided hoses including the damper jumper, and the section from the fuel filter over the torsion bar to the steel fuel pipe due to corrosion.

The coolant guage still doesnt move even though i have 12v at the sensor and connection at the near the fuse box. Gonna swap DMEs and ignition switchs to see if that fixes it.
Another thought is if mayby one of the relays in the FB is incorrect.

[Monkey Wrench]

I think if you look at the temperature guage basiacally as a volt meter that basically what it is.

as an example if you pick up an older analog meter, it uses the same needle ( gauge) for checking resistance, voltage and current. the difference is in the switching inside the meter . it applies different resistors (shunt resistors) so when you change the voltage scale you are employing different internal resistors.

would it be possible to separate the rest of the wiring and see if applying a small voltage to the gauge, lets say just power it off one or two DC flashlight batteries, see if the needle moves?

if you connect it backwards maybe youd see the needle move backwards so Id confirm polarity before sending it any appreciable voltage.

I think what is happening is the guage is provided power , it goes through the gauge and then to the temp sensor, the tempsensor is a variable resistor, the variable resistor is such that it is temperature dependant.

you could also check through the temp sender to ground and measure resistance through it and I would think that as the temp rises the resistance would be either greater or less. Point is you shoud see some reaction in terms of its resistance to ground, and that resistance changes with temperature.


when the resistance is increased , it is in series with the 12V battery so you have two voltage drops, ont through the guage itself one through the resistor then back to the battery. the sum of those two voltage drops is 12 V

because the temp resistor varies it's resistance by way of heat acting upon it ,thus changing its resistenace, well, since the two are in a series circut lower resistance means the resistor ( temp sender) takes a larger share of the 12 V and if it is no resistence the guage would see full 12 V any resistance that the sender presents shares the series load , leaving less , or more power for the gauge so the gauge reacts upon the voltage it sees.

it is labled as a "temp sensor" but I think t it is actually just a volt meter, with a painted dial representing the temperature, rather than "volts"

I think if you sub in a meter for the guage youd see some voltage differential which is dependant upon the temparture of the sender unit

so in theory of you were to re-paint the dial of a voltmeter so it represnted temperature it would then dispay engine temperature, where those marking s fall, thats callibration.


also try this, when the engine is warm, give the dash near the guage a "thwack" with your finger to shock it. sometimes the needle can be rubbing.so then the guage is itself mechanically stuck.


my volvo fuel guage does that, it will read Im empty, i fill up, no movement, then I give the dash a little thwack and the meter responds to half tank or full or what it is. the needle is definitely mechanically binding. I just live with it.

the fuel guage isnt; any different really except that the variable resitor is in the fuel tank.

when you have two loads in series, they share the voltage, they each have a voltage drop and the two voltage drops add up to 12 V

the sender is varying the resitance and the guage displays its share of the 12 V . you may say whats left of the 12V is what the guage sees.

the callibration is merely how the face of the guage is painted. I think if you just think of it as a voltmeter, it may simplify things.

there is some chance I am off on some of this so to all readers, do feel free to correct me if you do not agree with the explanation above.

I think you said you have 12 V at the guage, god, then the other side should have a variable resistance. a poor connection or wire break or wire rubbing through to ground may mess wiht the result. I bet if you ground that wire to the sender it will peg the meter, it is seeing no voltage drop then and the gauge would then see full 12 V and so the needle reacts by going to it's maximum scale.

usually with meters it is best not to try to make the meter needle go backwards or to force the meter to peg.

same will happen on an analog voltmeter if you are taking a measurement but you are on the wrong voltage scale or connect it backwards, this action can possibly damage a meter..

back in the early days of electrical bench work, a bench tech did likely not have fancy DMM's or multimeters . they took years to develop and he may only afford the one meter.

so insteead he would just use one meter and he would know how to use shunts to take various other measurements.

he'd be appying resistors and things , the modern analog meter just takes the hard thinking away, it still works the same way. its easier to set the switch to a certain voltage scale than to think about what resistor to apply.

digital meters or DMMs they will still show voltage but they use "magic electronics" some are "autoranging" so then you don't even have a switch to change the scale, the meter does it for you.

DMMs can sometimes present you with erroneus readings. it may for example measure voltage although the amperage is miniscule, so then you can get irrellivant readings,

for this Id use a basic analog meter. easier to watch the needle swing than read a bunch of flickering and changing numbers.. some DMM's do have a bar graph function thing to give a more analog representation.


nothing about the gauge is AC, frget anything about AC power here. it is just a DC voltmeter painted and callibrated as a temperature guage.

a user of a DMM may put his probes on something and there can be a DV voltage and as well some AC component. that can sometimes cause confusion.

as an example a 12V DC power supply for example or a battery charger makes DC but the power is probably not very well "filtered" by capacitors , then there may be DC but with a AC component, referred to as "dirty power" - you need clean power to for example run a radio but the power does not really need to be "clean" to charge up a car battery.

the car battery produces clean DC, the alternator may create dirty AC and the battery helps smooth out the AC ripple. when the car is not started the battery is providing clean DC.

i do not think the problems of the temp guage have anything to do with AC ripple. its just good to be aware you can sometimes see DC and and AC component from the same source. - just to avoid confusion for when you measure where both exist..

sometimes people get confused when using a DMM. and then realize they havent chosen the correc scale or swtitched the meter to the appropriate choice of AC or to DC

to confirm maybe just measure a 1.5V flashlight battery or a 9V then you can see the meter react, it just verifies it is working properly and as expected.

when working on home plant electrical work
Ill do that before I go trusting a meter to prove ther is or is not any power before touchign a wire.

Ill walk ot an outlet , and confirm yes theis meteer is able to measure 110. then I know the meter works and I am then more confident that I am not making a dangerous mistake. you can walk to the car battery and check the meter yes it is near 12 V so yes, the meter itself is functional. some cheap ones have intermittents loose batteries, cracked circuit boards, etc. you get what you pay for , Fluke is usually a good brand so I will not use on higher power like 600 V measurements, it doesnt; have high enough internal resistance protection.

a radio shack cheapo is fine for car use , usually.

it could be possible you have the wires to the guage swapped? that may try to drive the gauge backwards. same as if you had hyour meter probes reversed.