Factory temp guage markings/sending units?

[88 K30]

I am wondering what the numeric markings on everyone else's stock guage in a mid-80's truck read? I kept thinking my truck was running hot because of an aftermarket standard flow 190° t-stat. The stock guage is marked at 100, 200 and 240 and would consistently read between 200 and the next line (220), so it was about 205-210° while just cruising down the road at 35 or 65mph. The radiator was not that old, so I didn't think that was the problem.

While installing the Banks kit, I installed a RS 180° high-flow t-stat. At this point the guage started reading right on 200 under the same conditions. Given the fact that it was now consistently 10° lower than before and I had coincidentally put a 10° cooler t-stat in the truck, I was really questioning the stock reading.

I bought an aftermarket electric guage and installed it's sending unit in place of the stocker and wired the guage up. Took it out for a drive and it reads a rock-solid 180. Pulling a 2750lb trailer on a HARD pull (pedal down until I got to 65mph in a 50 zone and about 1000° EGT) up a long gradual hill, the guage got to about 190. Granted, this was only a 72° day, but I was fairly happy.

Aside from what markings are on everyone elses guages, what would cause the guage to read too high? I can see a typical increase in resistance causing low readings, but I am not sure about high readings.

From what I could find, gas an diesel sending units both have the same part number. Since I think it has always read high, I guess it could have had the wrong sending unit in it, but I'm not sure what it would be from? I'll have to check the number of the old unit and see if maybe it wasn't for this application?

Any thoughts are appreciated!

[Robyn]

Howdy

The Guages on most vehicles are more for adornment of the dash than for accurate measurements.

The fuel gauges are generally fairly close when the rigs are new as are the speedo
The oil pressure gauge is generally close BUTTTTTTTTT can vary depending on the time on the clock.

The temp gauge however seems to always be a bone of contention.
I have seen factory gauges read all over the sky.

The volt meters can be all over the map depending on where their feed comes from. :eek:

Your after market gauge is most likely accurate within a few degrees.
You can probably swap out the sender of the factory setup and see some changes.

Here is my take on it

Most people dont watch gauges and the factories know this. As long as the scenery is going by and there are no issues, all is well.
The average motorist probably never even looks at the gauges unless the rig starts running bad and by then if its a serious issue and the engine is toast anyway.
I have seen 3 different rigs of the same make and model with gauges that read totally different.

Now the diesel heads we have here at TDP are more apt to be watching their gauges and taking notice of whats going on under the hood than most.

You will find that few if any women ever look at the gauges other than the speedo and fuel gauge (I wont comment any on the later) :rolleyes:

Being a female I am an Island in the crowd of women as I was raised to do things with the boys and learned things a whole different way so I am a gauge hound and have raised my daughter to be one too.

In closing, just take stock in what the factory gauge says when the little creature is happy and then dont worry unless things venture from what it calls normal. :)

Or you can install a complete xtra set of gauges to keep your worries to a minimum.

Good luck and best to ya

Robyn

[88 K30]

Robyn,
Thanks for the reply. I am a diligent guage watcher as well, so this has always bothered me. I think I will just try to get the aftermarket guage to fit in the stock location and call it good. If it won't fit, it'll stay right where it is now under the dash. I just hate to have to look left and right to see all my guages, but if I have to, I will.

The last time I had the dash out, it looked like an aftermarket guage might fit in place of the stocker, but I didn't try it. This guage is 2 1/16, but I'm afraid it might be to deep. Anyone ever do a guage swap? What guage did you use?

Thanks again!

[Robyn]

The cluster will not allow any fitting of the aftermarket gauges.
Try another sending unit either factory or parts store replacement and see if your factory gauge works any better.
I do have some of the older style unit clusters and I could send you a gauge from one of the ones I have.
Post a pix of what your gauge looks like and I will see if I have one.
There were several different styles in the 80's

If the connections on the mylar circuit panel are dirty or loose it can really mess them up too.
Also where the plug goes in, if the copper tabs are oxidized your toast as well.

Remove the entire cluster and clean all the copper strips on the mylar as well as the matching prongs on the plug with contact cleaner on a Q tip

Robyn

[88 K30]

Robyn,
I'll have to take a look at my guage and verify the layout, but I know it has 200 in the middle position (straight up) and 240 on the hottest mark, with an orange section at about 230. Based on what I saw, if the guage said 180 in the middle position, it would be accurate. Have you ever seen any that are different?

Wouldn't poor connections at these points act like a higher resistance, causing the guage to read lower than it really should? That is what was so perplexing to me about this particular problem.

To be honest, I might just live with the current situation if the guage won't fit. It's a real pain to drain the entire system and swap sending units back to be able to use the stock guage again. Especially if it just going to be wrong with a new sending unit, too... :(

Thanks again!