So, trying to keep a long story short, wanted to upgrade my daughters instrument lights with LEDs, but also wanted to add a tach, so bought a full instrument cluster on ebay with all gauges to include tach and trip meter. Swapped in all the bulbs and pulled the old cluster (all gauges on the old were working with standard temp floating in the middle of the O on NORMAL, just left of center) and replaced with the new cluster.


Plugged in the new cluster (Red circuit board) and everything worked, tach was good, fuel and oil pressure all good, however new cluster temp gauge never really moved over past the left bar (to the left of the N in NORMAL) and never really even close to the N, I was sure the vehicle had hit its standard operating temp (I have the OEM 192 temp thermostat in the truck).


So, I unplugged the "new" cluster and swapped in the temp gauge from the "old" cluster since it worked before. Plugged it in and ran it up to operating temp, it was a little more responsive and actually came up to left of the N but that was about it.


I know most folks are going to say, just run a mechanical gauge and I agree with that, however I'm trying to keep the OEM look on the dash, so unless they make a mechanical that looks OEM, I would like to try repairing/diagnosing this.




1. How can I check to see if the "new" circuit board/gauge is working/reading properly?


2. I do have a mechanical gauge that I can use to verify the temp and will, as on the old cluster I can assume that Middle of the O is 192.


3. Do I just assume that now the new "Mean temp" is now the "N" and that my daughters worry point of overheating is around the "A" or "L"


Thanks in advance for your help

 

Try swapping the little box on the cluster. It's the voltage regulator for the gauges.

 

Franklin are you referring to the circled item??

 

Check the gauge by grounding the temp sender's wire. The gauge should go basically to the peg as 10 ohms is supposed to give full scale. And, if you can find one, use a 72 ohm resistor to simulate the temp sensor and you should have the gauge reading on the bottom mark. In fact, IIRC, 22 ohms should read right in the middle. But, these are not your standard 1/4 watt resistors as there's more like 2 watts of power being dissipated.

Part of the issue may be that you are using a different Instrument Cluster Voltage Regulator - assuming the new cluster came with one. It is the little metal thing a couple of inches long, held on with one screw and plugged into what looks like 9v battery terminals. Swap those and see if that makes a difference. The ICVR is notorious for causing gauge fluctuations so I'll bet you see a difference.

As for "mean temp", neither the N nor the O are as high as I'm used to for 192 degrees. Instead, I usually see R or M as the reading for that temp. And that's using a much more accurate voltage source than the pitiful ICVR to power my gauges. (I have a how-to picture album on making a replacement ICVR if you are interested.) That takes all the vaguery of the ICVR out of the picture, but the sending unit and the gauge itself are still variable. So, it is tough to determine the "correct" reading for these gauges, which is why many of us also run aftermarket gauges.

 

If so I can sure swap that.


Now that I think about it, the "Fasten Seat Belt" light used to light up for about 15-20 seconds, however the on the new cluster, it does not, I put a new (tested in the left blinker) LED bulb in there and tried 2 different ways to see if I could get it to light up after starting, it never worked, not sure if that is associated, and nor is it that important, just another mystery.

 

That's just another mystery. It may be that the seatbelt buzzer uses the current from the bulb to cause the buzzing, and since LED's pull so little current it may not buzz. And, you may have the bulb in backwards, meaning it needs to be turned 180 degrees in order to function.

 

So by grounding the temp sending wire I remove it from the sending unit and ground it to the block? Or while it is on the sending unit, use a jumper wire and ground both the sensor and wire?

 

Yeah tell me about it, the buzzer for seatbelts never worked, nor do I think it has one, I went through a while back and replaced the "Lights on buzzer" and I believe the seat belt buzzer was supposed to be co located with it, but it was AWOL. And I actually tried both ways (about 10 times) and could never get it to come on after ignition. Nonetheless, it was working prior to the swap

 

Either, but the easiest is to pull the wire of the sending unit and ground it.

On the seat belt buzzer, those things are frequently flakey. Rusty's works every once in a while. Dunno. Different problem.

 

Great will try it when I get home, agreed on the seatbelt light, not worth my time now, the temp gauge is the priority.

 

Keep a no contact infrared thermometer in the truck for those times when You want an accurate temperature reading. Just pop the hood, point and shoot the thermostat housing and voila! Accurate reading, no guessing.

Otherwise, after fussing endlessly with a variety of aftermarket stock style ICVR's (which were all crap BTW) I followed Gary's excellent tutorial and built a solid state ICVR with a pig tail just long enough for it to hang down for adjustment without pulling the cluster. But all I really did to calibrate it was fill up the tank, set the fuel gauge at full, and I haven't touched it since.

With the old ICVRs the temp would read A or L and sometimes wander even higher for fun and excitement, but now with the solid state ICVR it runs nice and steady between M and A.

 

Some day if you have the time I'd like to know what voltage your ICVR is set to. I found that 5.4v made the three sets of gauges I have go to full scale, but it would be good to hear of someone else's experience.

 

Ok so the when the temp sensor wire was grounded the gauge pegged all the way to the right (hot), from reading above that was a correct response for a functioning gauge.

Now what? Swap out the instrument voltage regulator? or should I swap, the temp sensor in the block? As noted from previous posts it always seemed to run low before the swap, maybe it is faulty or failing? I could have sworn I put a new one on it when I swapped the intake a while back.

 

Yes, that's the right response. So, swap the ICVR. But, my guess is that won't make a difference and the problem is the temp sensor. Did you use a lot of Teflon tape? The sensor needs to be able to be grounded.

 

probably and it is in an aluminum intake