Electrical Dash VOODOO!

[Wayne Waldrep]

View: https://youtu.be/6T8Bg3YnaCw


Took this vid today of my temp gauge. It's only 15 seconds long. In real time you can see the gauge almost bottom out then shoot back up to whatever temp that is. What you don't see is that it does this the whole time back and forth randomly. Normally my temp runs on the tick mark right beside the "A". In the vid when it goes up suddenly that's just a touch higher than normal running temp as shown on the lovely factory gauge. Over the last few months I've been trying to get some things worked out on my car. One of the things I hoped to fix was crazy gauge readings. I put a brand new braided steel ground strap from the back of the drivers head to the firewall. I went over all the other grounds in one big "ground wire" project. They are all good. The only thing that I did accomplish is the temp gauge no longer goes to the top when I turn the car off. It does still rise every single time I turn the headlights on. The headlights on are worth one whole tick mark higher...ridiculous I know. Most know from my other posts but just in case, every single piece of the cooling system is new over the last couple years. The car is not running hot. I always put my thermostats on the stove in water and check them before install even if they are new.
I'm not trying to figure out if my car is running at a certain temp. I'm totally fine with the cooling of the engine. But nobody wants to see gauges flopping around all the time. No matter how well prepared I have myself, seeing a gauge move drastically all of a sudden makes me cringe every time.
My thoughts:
-bad temp sender
-bad temp sender connector (Google these two numbers Standard S635 or Dorman 85845)
I really think it's in the instrument cluster because the oil gauge does similar theatrics at times just not as often. That gauge scared me to death a few years ago flopping around just like the temp gauge. I went to a friend's shop and screwed in a mechanical oil gauge and it was rock solid.
What do y'all think? If it is the instrument cluster what are my options. I can't just go buy Autometer gauges as much as I'd like to.

 

[DSB88GT]

Thought I may have read on here at some point that it could be a bad ground causing the erratic temp gauge. But, I could be mistaken.

 

[Wayne Waldrep]

Thought I may have read on here at some point that it could be a bad ground causing the erratic temp gauge. But, I could be mistaken.

Lol...you read it in my post above!

 

[General karthief]

Have you wiggled the connection at the sender while someone watches the gauge?

 

[Wayne Waldrep]

Have you wiggled the connection at the sender while someone watches the gauge?

I have no friends.





But....I'll definitely try it....lol. I also thought about something else. I've had my car apart an embarrassingly lot of times. I'm thinking I may pull the cluster and clean both large connectors and put some dielectric grease on em. Maybe I've just got a bad connection on one of those. Good idea or no?

 

[General karthief]

Good idea

 

[Wayne Waldrep]

Ok, I just spent quite a while searching old threads. I found them from 15 years ago or more. Lots of questions about erratic temp gauges (and for that matter oil and volts...whatever they technically are on these cars). I read lots of suggestions. Also read quite a few people that got them to act some better. Why with all the info and tech that we have do I not find a single time when an actual solution was found? Did I just miss all the ones that were solved? Lots of people "checked ground wires" but that sentence is not a solution. I know this because every single time this is posted we get the "check your grounds" advice. I've given it...lol. But my car has had a ground wire makeover if such a thing exists. It can't be grounded any better.
So you electrical whizzes and info junkies give me some details....Please.

 

[Olivethefet]

I have no friends.

If you have no friends you could tie a string to the connector get in the car and pull on it. It probably would get caught on something and wouldn't work. The things you have to do...

 

[Wayne Waldrep]

If you have no friends you could tie a string to the connector get in the car and pull on it. It probably would get caught on something and wouldn't work. The things you have to do...

LOL....excellent idea.

 

[EBW83]

I had similar issues in my '83 many years ago but my experience might not directly translate to your '88. My temp, oil, and fuel would slowly peg on the high side and this seemed to correlate to the AC blowing very cold. I could turn off AC and use vent and the gauges would slowly come back down. Internet searches pointed to the IVR or instrument voltage regulator. In my '83 the IVR was a mechanical "Reed" type regulator and if I remember correctly it could act erratically. At that time, I also found someone who had replaced the IVR with an electronic regulator and that fixed his issues. I basically did the same thing using a TI evaluation board for a 5V switching regulator. No more worries.

There can be contact issues as well especially when removing the cluster many times (like you and I have). The printed copper at the snap in connector can pull away from the flex circuit. Or, the connector spring contacts can oxidize making a bad connection. You can clean those contacts using your favorite method. You can also bend the connector contacts out a bit so they press harder on the flex circuit copper terminals. Here is a pic of my "kludge". New "IVR" at the bottom.

 

[Wayne Waldrep]

Nice post. Thanks for the reply. I'm definitely going to pull the cluster and clean up the two connectors and the film they touch. If I see where I can tweak the connector contacts a bits that's a good suggestion.
And.....as Bill O'Reilly used to say, Word of the Day...kludge! Nice

 

[jrichker]

Instrument cluster repair tip: The common super glue is a good tool to use to stick the copper foil back to the plastic sheeting when they peel apart. Super glue is also fairly heat resistant, so if you have to solder the copper foil, super glue is the thing to use to hold it in place.

The engine to block ground that goes between the intake manifold and the firewall is the alternator power ground for the gauges and everything else besides the starter. You may have a ground cable with a broken wire under the insulation or a bad crimp joint for the terminal ends.

 

[Wayne Waldrep]

Instrument cluster repair tip: The common super glue is a good tool to use to stick the copper foil back to the plastic sheeting when they peel apart. Super glue is also fairly heat resistant, so if you have to solder the copper foil, super glue is the thing to use to hold it in place.

The engine to block ground that goes between the intake manifold and the firewall is the alternator power ground for the gauges and everything else besides the starter. You may have a ground cable with a broken wire under the insulation or a bad crimp joint for the terminal ends.

Thanks! Remember the old ground thread that I found the error on to help you update it.....that ground is to the back of the head.
Anyway, the new one I just put on is one of those exposed braided straps. No insulation. Good to know on the super glue.