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Been trying to fix an issue with my coolant temp-gauge in the dash. It doesn't read the sensor anymore.
What it does, when engine is hot :
- gauge goes full max upon ignition-position, but goes back down all the way when engine runs.
- gauge goes full max upon accesories-position.
What I tried already :
- Ohmed the sensor ( cold around 300, hot around 20 ), so this is working as it should
- Jump-wired the lead to the gauge : gauge went up to full max
- Replaced the dash constant voltage regulator
I did this with the dash taken out and the speedo-cable off.
What am I doing wrong ? The only thing I can imagine is a faulty printed dash circuit. Is there any way to trouble shout that ?
Thanks guys.... ( plan B will be to install a separate gauge/sender, loose fro dashboard shenanigans...)
Martin
Checked the ground from battery to block and although it wat attached, the bolt seems to be the wrong size, so a bit wobbly. Will find a fitting bolt and will redo it. Also, the ground from block to firewall has seen better days. So will look into that as well. Found no ground ( yet ) from cab to frame and from bed to frame, so I'm going to install those as well.
Unless a PO (Previous Owner) installed the additional grounds, you won't find them. I extended the headlight ground & added a ground to the rad support. The inner fenders were rusty, so I ran a ground from the exterior firewall to the starter solnoide Using larger cables helps too, notice the 3 ground wires. Ground from battery to the frame (next to the vin) one to the alt. mount and one over to the driver side inner fender.
I have another ground from the driver's side inner fender to the firewall, so the frame, engine, fenders, and cab are all linked. I'll do the bed to the frame this year. Now we all agree that I went overboard with the size of cables. A 10 ga stranded wire would be more than large enough. Just clean the mounting area very well. I used stainless steel nuts, bolts,and washers; because I don't want to do this again.
Thanks for all the info guys, I'll dive into it and hope things get solved !
Bye,
Martin
So, new coolant temp gauge/sensor installed and working, yes ! Ground issues from battery to block solved and from block to firewall as well.
Next question : when I short my oil pressure gauge, it comes up all the way on the dash. But, no readings while engine is running.
Checked my printed circuitboard behind the dash and it gets 12V.
Can I test the constant voltage regulator which is behind the dash ?? Can I Ohm it in some way ? And what kind of readings should I get ?
You may have a oil pressure sender that has a broken membrane and the sender is full of oil. Disconnect the wire and connect an ohm meter to it to ground then start the engine and see if the value changes, if it does not then the sender is the problem.
The value changes indeed, when I start the engine and idle it, there is hardly any ohm reading ( multimeter set at 200M ). When I stop the engine it goes to about 150.
Have no clue if this is right or wrong to be fully honest....
Could be the wrong sender? Maybe for a light and not a gauge.
By shorting the wire to ground it is showing the wire back to the gauge is good and sender could be bad.
You say the temp gauge is not working as it should?
If so you might be able to use jumper wire and use the temp sender to test the oil gauge and the temp gauge the oil sender.
I know we can on the 80 - 86 trucks as the ICVR powers the temp, oil & fuel gauges and they change the face of the gauge to read what it is wired to.
Dave ----
Hi Dave,
The oil pressure worked before, so it's the correct one. But, the original problem was that it moved in sync with RPM's. So, hardly any pressure on idle and mega-pressure at 60mph.
So, now I have two questions outstanding :
- Can you test the correct working of a Instrument Voltage Regulator ?
- Does the dashboard need to be grounded for the gauges to work ( if that is so, I guess it would be through the speedo-cable ? )
Thanks again guys, it's good to have all your support !
Martin
Hi Dave,
The oil pressure worked before, so it's the correct one. But, the original problem was that it moved in sync with RPM's. So, hardly any pressure on idle and mega-pressure at 60mph. This could have been almost normal. Now with any factory gauge be it temp / oil or fuel they are just a gauge as to temp / psi / level and not 100% on the money. That is why it is best to run temp & oil aftermarket gauges as they do a better job. Also oil psi will go up & down based on RPM. low RPM the oil pump is not spinning fast so low psi. Higher RPM oil pump spins faster higher psi. You hardly see this with todays factory gauges.
So, now I have two questions outstanding :
- Can you test the correct working of a Instrument Voltage Cluster ?
- Does the dashboard need to be grounded for the gauges to work ( if that is so, I guess it would be through the speedo-cable ? ) I know there is on the 80-86 trucks to check the ICVR. You should have 12 volts in and think 4 to 5 volts out. This then goes to the temp / oil / fuel gauges then out thru the wires to the senders that change the resistance based on temp / psi / fuel level. Again on the later trucks there is a ground wire thru the cluster plug but I don't know on your year if so or not? If you been testing the gauges and the cluster is not screwed to the dash, how it would be grounded also if no wire thru plug, you can run a jumper wire from cluster to the body of the truck to test. I would not trust the speedo cable to be a ground. You have an outer & inner cable in 1. Inner not a good ground cable and the outer not much better as it is going to the trany mounted on rubber mounts. You say but it is bolted to the motor also in rubber mounts. But it does have the battery cable to it but that is a long way for the cluster ground to go. Run a jumper wire to ground and test again.
Thanks again guys, it's good to have all your support !
Martin
Thanks for your time ! Will run a separate oil-pressure-unit soon, as I don't want to take any chances. But, before that, I'll remount the dash completely and will run a ground from dash to frame to see if this solves the problem.
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