multiple questions: temp gauge, Anti-lock light and picture identify

[randomtask37]

I've got a few problems and I haven't had much luck trouble shooting so far. I have done plenty of searching and have not found my solution yet and I'm hoping for ideas of what to check next.

1. Cluster water temperature gauge not functioning.

It has not worked since I bought the car. It never budged (even a flicker) out of the 'off' position in the blue. The rest of the cluster worked fine. I have an aftermarket gauge in the ashtray location to make sure I am not overheating. I recently replaced my timing belt, water pump and thermostat. This did not solve the problem.

Ill take you through the steps I've taken.

First I removed the cluster and checked the ground nuts on the back of the gauge cluster. They were tight, but I went ahead and removed them, cleaned and re-installed. Reinstalled the cluster, didn't fix the the problem
Second, I checked the thermostat sensor/sender and connectors. The connector wires are not frayed and look fine. The connectors are holding tight, the plastic seams to be strong and the pins don't look eroded. So I replaced the sensor and sending unit with brand new ones from pelican parts just incase they had gone bad. Didn't fix the problem
Third, I replaced the cluster and double checked the ground nuts on the back of the cluster. When I first cranked up the car, the temp gauge immediately bounced around (appeared to me to be malfunctioning.) I wasn't sure, so I took the car out for a drive to heat it up. While i was out, the gauge quit bouncing around and shot into the red (topped out). My aftermarket gauge displayed a normal operating temperature, so this is clearly a malfunction. But at that point I'm thinking, well at least its moving. So the next day, while Im driving to work, its pegged to the red and out of nowhere it dies and drops back to the blue bottom.
Ever since then its been stuck at the bottom. It doesn't bounce around malfunctioning like it did when I first cranked up the car with the new cluster. But i did notice when is started the car this morning is just barely bounced off the bottom for a split second. Everything else in the cluster works fine, so I do not believe my SI board is dying.

What should I check now? I am kinda at a loss.


2. Anti-Lock light permanently on once key hits on position

When I installed the 'new' gauge cluster (mentioned in #1) I noticed my Anti-Lock light was staying on permanently once the key hits the on position. I think, well thats new. So i go and check my old cluster and see the bulb had been pulled from the anti-lock spot. (thanks PO for mentioning that when i bought the car... dick)

First, after researching, I find the most common cause of this symptom is a failed ABS relay. So like an idiot, i ordered a new ABS relay without checking to make sure the old one failed. I replaced the ABS relay with a new one from pelican parts. After replacing, i opened up the old one to find there was nothing wrong with it. that 'fuse' wire was not broken. Solid waste of 40$. Now I'm not sure what to check. I guess I need to check wiring and the other relays, but I don't know where they are or how to check them. Are they paired with the ECU or in the engine bay near the ABS unit? I took some picture and hoping you guys can help me identify what im looking at.

are these the other ABS relays? if not, what are they? this is located above the abs unit and next to the coolant tank


I followed some wires coming through drivers side front wheel well hole and traced them to this connector. What is this.... and should there be something attached to it? It was hiding under my fuse box.

zoom


zoomed out


what is this thing im holding. should there be additional fuses in it? When i opened it the fuse wasnt sitting firmly in the connection. (after re-seating the fuse restarting the car i saw no changes in anything)

[Gregs///M]

#1 The temp gauge can be tested as follows. With the ignition on, car off, disconnect the temp sender from its connector. The gauge should read full cold.

Then ground the pin (brown/violet) wire to ground, the gauge should read full hot. If you experience different behavior, then you can assume there is a short or open circuit in the wiring or something wrong with the cluster.

Also, be sure you have a cluster that is verified working from another car or has an SI board with new batteries. I know the rest of your cluster gauges work but with dead batteries, anything can happen. The cluster can act weird in many ways with dead batteries, sometimes only tach fails, sometimes only MPG fails, sometimes all of them fail. If you're using an SI board with the original 20+ year old batteries, that could be your problem right there.

To get more in depth, you can measure the resistance at the sender. It should be near 1000 ohms at room temp. You should also be able to see around 1000 ohms at the gauge input (same brown/violet wire on the blue connector.)

Since your gauge has been intermittently peaking to hot, when the engine temp is verified at normal, one can assume there is a short to ground in the wiring. Inspect the wiring too.

#2. I'm not too much of an ABS expert so maybe someone else can chime in. But I would first check to make sure all your ABS components are plugged in. A fault in the ABS system can simply and easily be something the PO disconnected.

Download the electronic troubleshooting manual and bentley repair manual from this site so you can see the diagrams of the ABS system. It will help a lot.

The extra connectors at the fuse box is for auxiliary fusing. Its normal to find nothing connected to it.

[randomtask37]

Thanks for the help. Ill try that stuff in the morning. Im much more mechanical minded, so electrical stuff like this is more challenging for me.

[randomtask37]

When I tried your method to ground The temperature sensor plug, the gauge did jump into the red. Does this mean that most likely my batteries in the cluster are dead?

[randomtask37]

accidental double post

[randomtask37]

TEMP GAUGE list - this is gona help me keep track of what ive already done.

#1 The temp gauge can be tested as follows. With the ignition on, car off, disconnect the temp sender from its connector. The gauge should read full cold.

Then ground the pin (brown/violet) wire to ground, the gauge should read full hot. If you experience different behavior, then you can assume there is a short or open circuit in the wiring or something wrong with the cluster.

--- DONE - bottom (blue) when unplugged & top (red) when grounded

Also, be sure you have a cluster that is verified working from another car or has an SI board with new batteries. I know the rest of your cluster gauges work but with dead batteries, anything can happen. The cluster can act weird in many ways with dead batteries, sometimes only tach fails, sometimes only MPG fails, sometimes all of them fail. If you're using an SI board with the original 20+ year old batteries, that could be your problem right there.

--- The second cluster I installed, i was told was working correctly. But, I will install new batteries soon if i cant get this thing working any other way.

To get more in depth, you can measure the resistance at the sender. It should be near 1000 ohms at room temp. You should also be able to see around 1000 ohms at the gauge input (same brown/violet wire on the blue connector.)

--- I have not checked resistances yet. Once i get a few minutes to pull the cluster again i will

Since your gauge has been intermittently peaking to hot, when the engine temp is verified at normal, one can assume there is a short to ground in the wiring. Inspect the wiring too.

--- I have visually inspected the wiring best i can. I havnt found any breaks, but soon ill test resistances to make sure


I followed some of your advice from another thread, but still no luck.
"Here are some tips for you guys with gas gauge and coolant gauge problems. This assumes you have tested the sender's via Bentley manual specs and procedures.

1. I would first pull the cluster out and tighten the 7mm grounded nuts directly behind each gauge. This is the primary ground for each gauge.

--- DONE when i installed the second cluster

2. Above the brake pedal, under the dash, there is a bracket with two 10mm nuts on it. The upper nut is the ground rings for the cluster. The bottom nut is the ground rings for the power windows and illumination circuits. I recommend that you remove these two nuts and clean each ring lug as well as the ground stud with a wire brush. After 20+ years, these can corrode. Don't just look at it and assume it is OK. You must actually remove them and inspect each side of the ring lugs. You might find your cluster gauges become more accurate (if grounds were corroded) and your windows travel faster.


--- DONE. Today i took a wire brush to every ground i could find. 1. Engine ground. 2. The connections attached to the firewall next to where the convertible battery tray sits. 3. the passenger side strut tower 4. the two nuts you referred to in the dash above the pedals. - for each spot, i removed the nut and took a wire brush to the nuts, the wire connectors and the ground plate/wall

3. This applies mostly for the coolant gauge. Check the condition of the Engine to Chassis ground cable. On the M20, this mounts from the oil pan to the frame rail on the drivers side. This cable can be corroded and oily from so many years. Replacing it would help electron flow. The cable can be be cleaned enough to crank the starter over because of the huge current load, however it can cause electrical resistance in the circuit if dirty, causing inaccurate coolant temp feedback. This cable provides the primary ground loop for all engine related electronics.

--- DONE

4. Lastly, if these tips do not work. I would look into cluster inspection. The cluster main board is well known to develop cracked solder joints that are so small you might need a magnifying glass to it them. Also the gauge themselves can develop the same.

--- sort of DONE. Ive looked over the board but dont really know what to look for. i am not seeing any obvious breaks.

5. Measure voltage across SI board batteries. Each battery should be a minimum of 3 volts DC. Each current load should be 300mA minimum. Current load must be tested with the batteries removed from the circuit/SI board.

--- have not done. I have an extra SI board out of the car right now i could test this first, and swap boards if necessary. I took one of the batteries out but it was a real bitch to remove. Im afraid i may have damaged something just trying to get the battery pulled.

6. If all else fails, inspect the physical wiring. Measure resistance across the wire, you should see near 0 ohms and no breaks.

--- visual inspection - not with multimeter yet

[randomtask37]

i checked the volts at my battery just now thinking maybe my alternator is to blame. after my 1700 mile road trip last week i noticed a speed sensitive whine coming from somewhere in the front of the car. I initially thought maybe it was a wheel bearing or something, but alternator also came to mind. the whine doesnt come through the speakers. I can drown out the noise with my stereo

car off: 12.5v
idle: 14.5v
idle, headlights on: 14.3v
1500rpm: 14.3v
1500rpm, headlights on: 14.2v
idle, stereo bumping: 14.3v
idle, stereo bumping, headlights on: 14.18v

does this look normal? operating between 14.1v-14.5v seems high to me. I always heard 13v-13.5v is normal. Is this a problem? Could it be a contributor to my anti-lock light always on?

[Gregs///M]

i checked the volts at my battery just now thinking maybe my alternator is to blame. after my 1700 mile road trip last week i noticed a speed sensitive whine coming from somewhere in the front of the car. I initially thought maybe it was a wheel bearing or something, but alternator also came to mind. the whine doesnt come through the speakers. I can drown out the noise with my stereo

car off: 12.5v
idle: 14.5v
idle, headlights on: 14.3v
1500rpm: 14.3v
1500rpm, headlights on: 14.2v
idle, stereo bumping: 14.3v
idle, stereo bumping, headlights on: 14.18v

does this look normal? operating between 14.1v-14.5v seems high to me. I always heard 13v-13.5v is normal. Is this a problem? Could it be a contributor to my anti-lock light always on?

Your alternator looks normal. Anything over 14v is a good sign. My car has the OEM alternator and the most volts I can get is about 13.5. Im in dire need of a rebuild. I would move away from the alternator as the suspect.

From what I've seen from your troubleshooting, I would suspect the SI board batteries as the culprit.

Do not trust anyone who say's their 22+ year old cluster "works perfect" unless the Si board batteries have been replaced with new. The SI board batteries were not designed to last two decades.

I would discontinue any additional troubleshooting until you replace those batteries.

[randomtask37]

multiple questions: temp gauge, Anti-lock light and picture identify

Well I got the new battery si board back from you yesterday and installed. However this did not solve my core problem of the temp gauge not working. My gas gauge works like it should now though

I did notice the main board in the cluster had 2 lines that looked ...burned. Not bad, but it got me thinking

[Gregs///M]

Yes, the cluster main board commonly has burnt traces. Often those are broken or "open" traces also. Be sure yours temperature gauge sender is within spec. Should read around 1000 ohms at room temperature.

Also make sure the 7mm nut behind the gauge is tight.

[randomtask37]

The sender as in the unit attached to the thermostat? If so I will measure it but it is brand new so it should be fine. I'm back to thinking I've got a short or break somewhere. Can I run new wires for this thing? Do you know what wires at the... I guess cluster blue plug I'd need to use?

[Gregs///M]

The wire is brown/violet in the blue plug.

I would say it is much more likely you have cracked solder joints or broken traces on the cluster main board.

You can send me your cluster if you need testing and a quote for repair. Most electrical repairs are under $100.

[randomtask37]

I have the original cluster that came with the car. This weekend i will swap SI boards cluster to cluster and see if that fixes the problem. If not ill probably send you 1 of the clusters

[randomtask37]

1 problem down. I FIXED the ABS issue. Turns out the fault was in the ABS unit relays (the 2 relays attached the the ABS pump itself). I took the 2 relays from a junk yard 91 vert and swapped them in. I really didnt expect this to fix the problem, but BAM no more light. I test drove and slammed the brakes and felt the kick. Thank god, 1 down.

Now, for the temp gauge. Greg, I used the fixed up SI board you took care of, in 2 different clusters. (2 different main boards). #1, gauge stuck at full blue. #2, first install i forgot to install the ground nuts on the gas & temp gauge. When i turned the key, the temp gauge jumped to full red and stayed there. I remembered I hadnt put the ground nuts on, so i uninstalled, put them on and reinstalled. With the nuts on, the gauge was again stuck at full blue.

Sounds like you believe the main boards are to blame. What are the chances both main boards are crap? I have the cluster i want to use boxed up ready to send to you if you believe this will fix my issue. I guess if nothing else, after you fix the main board, the whole cluster will have been repaired and i can eliminate the cluster from my troubleshooting.

[Gregs///M]

1 problem down. I FIXED the ABS issue. Turns out the fault was in the ABS unit relays (the 2 relays attached the the ABS pump itself). I took the 2 relays from a junk yard 91 vert and swapped them in. I really didnt expect this to fix the problem, but BAM no more light. I test drove and slammed the brakes and felt the kick. Thank god, 1 down.

Now, for the temp gauge. Greg, I used the fixed up SI board you took care of, in 2 different clusters. (2 different main boards). #1, gauge stuck at full blue. #2, first install i forgot to install the ground nuts on the gas & temp gauge. When i turned the key, the temp gauge jumped to full red and stayed there. I remembered I hadnt put the ground nuts on, so i uninstalled, put them on and reinstalled. With the nuts on, the gauge was again stuck at full blue.

Sounds like you believe the main boards are to blame. What are the chances both main boards are crap? I have the cluster i want to use boxed up ready to send to you if you believe this will fix my issue. I guess if nothing else, after you fix the main board, the whole cluster will have been repaired and i can eliminate the cluster from my troubleshooting.

Cluster main boards have solder cracks and breaks all the time. You can send to me to test if the problem lies in your clusters or your car wiring.