Temp Sending Unit? (5 Viewers)

[Spike Strip]

I'm not an electronics guy - in fact, I hate just about anything where I have to think about what the electronics are doing. I'd rather watch Nancy Pelosi put on makeup than figure out a schematic.

A lot of people experiencing perceived over-heating are really just seeing an inaccurate gauge because of that goofy VR setup....

I solved my gauge issue with an in-line resister (15 ohm, IIRC), in the single lead to the temp sensor in the head (stock gauge always reads low, though), and an aftermarket temp gauge, but I'd sure be interested in a drop-in (or relatively simple) fix for the VR thingy in the cockpit. I think others would be, too.

 

[Spook50]

I'm not an electronics guy - in fact, I hate just about anything where I have to think about what the electronics are doing. I'd rather watch Nancy Pelosi put on makeup than figure out a schematic.

A lot of people experiencing perceived over-heating are really just seeing an inaccurate gauge because of that goofy VR setup....

I solved my gauge issue with an in-line resister (15 ohm, IIRC), in the single lead to the temp sensor in the head (stock gauge always reads low, though), and an aftermarket temp gauge, but I'd sure be interested in a drop-in (or relatively simple) fix for the VR thingy in the cockpit. I think others would be, too.

You're dead-on right about the inaccurate readings. First time I saw it I was cruising along on the freeway with no exit in sight and saw the temp gauge suddenly max out. Fortunately before I actually soiled myself I saw the fuel gauge spike too and put 2 and 2 together. Then I was just irritated

My new regulator will work to completely eliminate the spiking and bypass the breaker points style regulator. I'm designing my third prototype right now, which should be a drastic departure from my first two attempts. I'm still trying to find the best balance of space saving, tolerance for extreme temps under the dash, secure mounting setup and end cost of the assembly. This is good experience for my electronics engineering degree that I'm taking a course for right now too

Once I'm close to having a final version I'll post up a thread about the design process for anyone who's interested to read. Hopefully by then I'll have an idea when I'll have units to actually sell too.

 

[Spike Strip]

Sounds great! Keeps us posted. If you need a gauge to experiment on, lemme know. I prolly got a spare around.

 

[Spook50]

I've been experimenting on my own while I've been able to drive the Avalon and afford downtime for the Cruiser. Problem is that the resistance that the FSM shows for the senders is no where near the resistance I'm encountering with the stuff in my own truck. My senders have way higher resistance. I could see if one was going out and off from what's spec'd in the FSM (or even a small percentage of error tolerance for a brand new sender), but with both I'm going off the assumption that mine are working as they should. When I had my gauge cluster out of the truck and hooked up in the lab to test, it was responding spot-on to 3.5V. Obviously that wasn't the case when I tested my first prototype in my truck.

Once I have the right voltage for my truck's gauges, I'll make an identical prototype for someone else to test on their gauges and make sure they're responding correctly.

 

[Spike Strip]

I remember when I was trying to troubleshoot this my resistance values were all over the place, too.

Well, keep us posted on the fruits of your endeavor and take pix!

 

[lugueto]

You have a loose contact my friend.

Check the wires that run from the fuel and temp gauges to see where theyre damaged or disconnected, a loose contact or ground on these wires will cause the gauge to act this way.

 

[Spook50]

You have a loose contact my friend.

Check the wires that run from the fuel and temp gauges to see where theyre damaged or disconnected, a loose contact or ground on these wires will cause the gauge to act this way.

That would be the likely cause if the gauges were dropping and then recovering. The fuel and temp gauges are grounded through their senders, so losing contact in that path = no current = needles drop. The spiking is caused by the contacts sticking and allowing full voltage to go through the gauges until the force on the thermal spring (which controls the contacts) is strong enough to pull them apart again. Worst case scenario is this could fry one of the gauges and end up calling for a replacement. I'm trying to develop a fairly easy to install permanent fix for it that completely eliminates the mechanical regulator. It's slow going because of our tight budget, but I am making progress.

 

[langsen]

...

Anyhoo, that black cylinder is actually a small inductor. I've seen other small DC inductors that look exactly like that so I hooked it up to a function generator in our lab and hooked up the oscilloscope in parallel and sure enough, it tested out as a 91uH inductor. Here's a similar one without the shrink wrap cover that's rated for 95uH: http://www.digikey.com/product-detail/en/682AE-014=P3/TKS1200-ND/260059

I'm curious what the manufactured spec and tolerance were. That and I wonder why they bothered putting an inductor on a mechanically switching DC regulator when a capacitor would've made a lot more sense in this application to "smooth out" the voltage fluctuations.

As I understand it, the capacitor smooths out voltage fluctuation and the inductor smooths out current fluctuation to control ripple current.

 

[Spook50]

As I understand it, the capacitor smooths out voltage fluctuation and the inductor smooths out current fluctuation to control ripple current.

I'm thinking you're right, since it's the current, not the voltage that actually heats up the element wire to move the needles. In that case, now the use of an inductor makes sense. There is a capacitor in that gauge assembly, but it's only connected to the voltmeter so that one's not even relevant to the fuel & temp gauges.

Update on the voltage regulator project: Next batch of components I need for the next series of prototypes will be ordered hopefully this week. I got an idea that'll solve one problem I've been having and help make for a cleaner end product (and easier installation).

After this I'm buying replacement dash plastic for my 62 because DAMN mine's annihilated!

 

[Spike Strip]

There were some important pix in post #46 that are now missing -- If I can find them, I'll repost. However, the do-dad that Spook is working on will replace any of the above tinkering.

 

[MicahMan]

I love do dads that fix tinkering!

 

[Spike Strip]

Spook, how's the do-dad coming ?

 

[ward93]

whats the best mechanical temp gauge to get that a college student with no money can afford. i don't want auto zone crap but i can't afford the 200$ ones the people on youtube suggest.

 

[ward93]

whats the best mechanical temp gauge and place to install it on a 62

 

[gregnash]

Really depends on what you want... plenty of different brands out there from house brands at JEGS and Summit to the cheapo Sunpro. I recently bought a BOSCH vacuum gauge and it seems to be very quality built. They offer a Temp Gauge as well as others.

For mounting, well that is up to you and your imagination.

 

[ward93]

thanks!!

 

[Komanche]

IT WORKS!!! On my 24V HJ60, it is working like a charm. Thanks for great info.

My partslist:
STM L7805CV-DG
Assmann V5338
Assmann V7236C cooler, but it seems it is little bit overheating...
so I added one more cooler

 

[Komanche]

It is not nice, but it works

 

[Spike Strip]

Nice. Is that the same Volvo Voltage Stabilizer chip that @VTCDN used, but in a heat sink?

( Volvo Voltage Stabilizer 240 260 760 or OEM 1362674)

 

[Komanche]

it is STM L7805CV-DG