temp gauge pegged (1 Viewer)

[island45]

After my rewire all gauges worked but the temp rises slowly and always pegs on hot. I know it isnt hot because i can hold my hand on the radiator and it pegs so quickly. I tried another sender from an '83 block and it acted the same. There are 2 senders about 6" apart, so it's a bit confusing. It's a '76 2f. I switched the sender at the rear of the block because it seems thats the one that goes to the gauge. What do I try next? Thanks

 

[rsbcruiser]

If you take the temp sender wire and ground it, bet the temp goes to full. Maybe you are getting a partial ground on that circuit. Hey Island, hear about the tall ship that grounded on your island? can,t believe they didn't sink it, not too many places there friendly to ship groundings. One other thought. If there is air trapped in the head then that would cause the temp to look high. Maybe vent the head by disconnecting the heater hose.

Richard

 

[island45]

Thanks. After work I will try to vent any air from the system. One other clue is that when these gauges were in the '76 donor vehicle, the temp and fuel gauge both stopped working at some point while I owned it. After filling the gas tank in the 45 last night for the first time, it registers just a bit over 1/2 and I know it's full. So the the fuel gauge AND the temp gauge are operating,but wrong... Maybe a common grounding problem. They both worked fine in the '76 when I bought it last January. Also I am using the original tank and sender from the 45 and connected to the later model gauge. And the sailing ship thing. I gotta agree. It's not like it would hit a sand bar.... more like a rock bar. We all refer to our island as 'the rock'.....

 

[spotcruiser]

Hi Gary,

IIRC, one of the two temp sensors in the head is a sender for the gauge and the other is a switch for emissions control. One should be red and the other green (plastic potting around terminal) and I believe the emissions control switch is red. You want the gauge hooked up to the sender, of course. You can pull both of them and test them in boiling water. I think the switch is open above ~130 F. The sender resistance will vary from 90 ohms at 140F to 27 ohms at 212F, per the FSM.

For the fuel gauge issue, the old senders are not compatible with the newer gauges. IIRC, their functions are reversed, resistance-wise. You need to install the later style fuel sender to match the 76 gauge.

Todd.

 

[radioridge]

fj62s have a common problem of the temp gauge and fuel gauge both peging . i dont know if its the same problem but you may gain some insight from a search in the 60 section

 

[rutbeer]

Hey, old thread, but I am experiencing issues with my fuel and temp gauge at the same time. I put a new CCoT tank and sender in and it was fine when only 2 gallons was in there. When I filled the tank to about 3/4" the temp and fuel gauges quit working all together. The oil and amp gauge still work, and looking at the Haynes wiring diagram, the oil, gas, and temp gauge all share the same power lead. I have not pulled the cluster just yet, but will probably do that tomorrow to test everything out. Of course, if it's a common ground issue, that would be WAY easier to fix.

 

[rutbeer]

Figured it out. Early clusters have a wire that jumpers between each gauge to power it. Later clusters have a circuit board of sorts that link them. On the fuel gauge back, there are three posts. The third, center, post is the one that pushes power to the temp gauge. There was no power on that post, so I pulled the cluster apart. There is a hair spring of sorts that makes that connection internally....it just needed adjusting and cleaning. PRESTO! I have fuel gauge and temp gauge again.

 

[MuskieFJ]

Rutbeer, did you happen to get a picture of the guages? My temp guage pegs when I idle and have lost all movement in the Fuel guage.

 

[rutbeer]

Nope. What year do you have? On my 78, the gauges are powered on one side, then connected to "ground" on the other. The ground just happens to be interrupted via the sensors, which give a variable resistance depending on the measure. A gauge pegging at idle might suggest that either you really are getting hot, or there is a voltage supply issue to the cluster. Changing the input voltage to the gauge would probably alter it's behavior relative to it's "ground". Just guessing here.

As a general rule of thumb, I ALWAYS check and clean all the grounds in a circuit before troubleshooting anything else. About 8 times out of 10, that's what it is. To check that, I run a simple ground with two clamps on it to bypass the normal ground. If that fixes it, then there you go.