Fuel and Temp Gauges (1 Viewer)

[cruiseroutfit]

I don't see why these gauges would need regulated power other than the chassis power that is already regulated. If there is a regulator, it isn't indicated in any of the schematics.

From what you can see in the picture, I can't see how this "switch" device would function as a VR. It seems more likely to be some way of adjusting the full scale swing of the meter.

What side of the "switch" is the center post connected to? Can't really see this well in the pictures.

When the switch is closed, it sends the power to the top-middle post, which in turn powers both the fuel guage coil and the temp guage coil, I don't see how it could act as an adjustment at all. Either the two guages have power (via the switch) or they do not, nothing in between that I can see??

Here is a better pic of the inside:

And a pic with my awesome details:

 

[cruiseroutfit]

Update:

The switch does act as a voltage regulator of sorts. As pointed out, these guages do not run at a full 12V, if they do, they immediately "peg out", run the voltage back through the "regulator switch" and you have guages working just as normal. I tried to determine the voltage through the switch, but it bounces between 0 & 12V, it must give the guages an average voltage, fast enough that the guages don't have time to react to the alternating voltage. Interesting to say the least. Assumable one could knock the voltage down to say 7V (hear that number somewhere) and be good to go. I cleaned my the contacts on my switch with a small torch tip cleaner and it is working 100% now (20+ trials with no failure). That explains why me "knocking" on the cluster fired them back to life. In hindsite I would run a different cluster, just to eliminate the issue... but its worked for almost 40 years, a little cleaning was well deserved

One item I didn't point out above was the ground on the back of the guage, the small copper/brass tab touches the instrument cluster housing. If it is NOT working, the guages immediately peg out with the key (they are getting a full 12V as the switch isn't cycling). Neato.

I'd still love to have someone else verify this...

 

[Pin_Head]

I agree.

Since the coil around the switch arm is grounded directly, I can see how this could function as a voltage regulator. It isn't indicated in the schematic, but then again, some other complicated things like the hazards are only indicated by a box.

 

[Rocky_LC]

On my '74 (and in My Hanes Manual) There is a description of how to check the Combination Meter. The checks are described in Section 11 (Electrical System), Section 17 (Combination Meter Testing).

The way things work is there is Power coming into all the meters on the Violet / Red Wire in the circular plug on the back of the instrument cluster (Haynes Labeled it "From Ignitions Switch" in Figure 11-49) - if this power is not there, all my Oil Pressure, Fuel , Temp read "0" (To Left).

The Fuel guage reads resistance - More resistance = less fuel. If the sensing curcuit sees a short - the guage reads way over "Full" (Pegged to right of guage.

Here's the Haynes Combination Meter Check:

NOTE: You need a Haynes Manual to find Pins A & B... Sorry

1. Check Battery Connection to Combination Meter by measuring Pin "A" to Ground. you should see the voltage at Pin "A" fluctuationg between 2 & 7 Volts. (** Kurt - this is the "regulated voltage supply" you identified **)

2. If you don't see the 2-7 Volts fluctuating, check the resistance Pin B to Ground (should be 25 Ohms or less). This is the fuel sender resistance (25 Ohms is full).

Good Luck

 

[sparkplug]

I have had the same problem and it was on the plug going into the cluster. It was not just the connection going into the cluster but the wires going into the (male-female? can't remember)plug. Check for continuity on the pins on both sides. Good luck.

 

[cruiseroutfit]

On my '74 (and in My Hanes Manual) There is a description of how to check the Combination Meter. The checks are described in Section 11 (Electrical System), Section 17 (Combination Meter Testing).

The way things work is there is Power coming into all the meters on the Violet / Red Wire in the circular plug on the back of the instrument cluster (Haynes Labeled it "From Ignitions Switch" in Figure 11-49) - if this power is not there, all my Oil Pressure, Fuel , Temp read "0" (To Left).

The Fuel guage reads resistance - More resistance = less fuel. If the sensing curcuit sees a short - the guage reads way over "Full" (Pegged to right of guage.

Here's the Haynes Combination Meter Check:

NOTE: You need a Haynes Manual to find Pins A & B... Sorry

1. Check Battery Connection to Combination Meter by measuring Pin "A" to Ground. you should see the voltage at Pin "A" fluctuationg between 2 & 7 Volts. (** Kurt - this is the "regulated voltage supply" you identified **)

2. If you don't see the 2-7 Volts fluctuating, check the resistance Pin B to Ground (should be 25 Ohms or less). This is the fuel sender resistance (25 Ohms is full).

Good Luck

Very good, that answers that... My cluster is not the uni-pin connection (non-circuit board type) that started in 9/73' I believe, so I didn't really look to much in the later FSM's, but that helps alot. Thanks!

 

[cruiseroutfit]

I agree.

Since the coil around the switch arm is grounded directly, I can see how this could function as a voltage regulator. It isn't indicated in the schematic, but then again, some other complicated things like the hazards are only indicated by a box.

The schematics are pretty vague sometimes arnt they

I guess they are correct as to the letter of the law... you do supply them with 12V. Where they fail is in that they do not show the kicked down voltage from the fuel guage powering the temp guage. Could easily confuse anyone

 

[dfmorse]

The voltage regulator schematic is shown in FSM 98154, pg 12-26, fig 12-53.

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[cruiseroutfit]

The voltage regulator schematic is shown in FSM 98154, pg 12-26, fig 12-53.

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Any chance you can post a pic?

 

[dfmorse]

Sorry, no pic capable here.

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[Spike Strip]

Just to cross-post this in this thread, since it's referenced in the 60 section. Fuel and Temp gauges are similarly powered. Insertion of a solid-state voltage regulator to replace the mechanical one.

Starting around post #27 or so...

https://forum.ih8mud.com/60-series-wagons/27578-temp-sending-unit-2.html

And to add:

 

[Spike Strip]

https://forum.ih8mud.com/40-55-series-tech/481728-gas-gauge-temp-gauge-suddenly-dead.html

 

[cruiseroutfit]

Thanks for the update Spike. Since I cleaned my setup I've not had any further issues and have since helped a few customers diagnose similar issues.