78 Bird gauges stuck

[78birdquestions]

hello. It's great to be here.

Today, I test drove a one owner 78 with a 351. Excellent garage kept condition. Took it on a nice test drive and she moved very well. A couple of things stood out, though.

The gas and temp gauges didn't mover from E or C respectively. In talking to the owner, I found out that it was his dad's car, and had not really been driven regularly in about ten years. It would come out about 4 times a year. I'm wondering if maybe these gauges are stuck due to lack of driving, and more regular use would help. Everything else works fine (AC seems to be seized up). Even the 8 track.

What are your thoughts here? Are they easy fixes? Thanks.

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[Milepost202]

I had a similar issue with the first 79 T-Bird I had. At the time I was working in a Ford dealership. I pulled the sending unit from the tank and found the float had corroded. I replaced the entire sending unit, although realistically, I probably could have just replaced the float and it would have fixed it. U might want to look at replacing the sending unit for the temp gauge. Both parts should be able to be had at any parts store.

 

[Don Holton]

hello. It's great to be here.

Today, I test drove a one owner 78 with a 351. Excellent garage kept condition. Took it on a nice test drive and she moved very well. A couple of things stood out, though.

The gas and temp gauges didn't mover from E or C respectively. In talking to the owner, I found out that it was his dad's car, and had not really been driven regularly in about ten years. It would come out about 4 times a year. I'm wondering if maybe these gauges are stuck due to lack of driving, and more regular use would help. Everything else works fine (AC seems to be seized up). Even the 8 track.

What are your thoughts here? Are they easy fixes? Thanks.

I concur with milepost 202 that the fixes recommended for those items are more than likely the issues at hand. The temp sending unit is an easy fix just replacing the engine based temp sending unit should bring back the Temperature gauge issue. The fuel tank sending unit would be a bit more of a job but if at all possible I would replace the entire gas tank sending unit as these are common failed components on these cars!

 

[daytonthunderbird]

Where is the temperature sending unit on the 351M (400) engine? I've been told it is located on the back of the engine on the intake manifold but didn't find anything back there except for the oil sending unit. I saw what looked like one on the front of the engine behind the alternator which had a double connector on it. There are also two other things with vacuum fittings in the intake near the front of the engine. My temperature gauge will not move off C and I would like to get this working.

 

[captrick]

The temperature sending unit should be around the top radiator hose or thermostat housing. Before you start going crazy trying to find the problem check all the electrical connections. Being the car hasn't been used that often it could be just a dirty connect. Start with the easiest repair and work to the hardest. It is never simple to find the problem you have to make the fix simple. Good Luck Rick

 

[daytonthunderbird]

The temperature sending unit should be around the top radiator hose or thermostat housing. Before you start going crazy trying to find the problem check all the electrical connections. Being the car hasn't been used that often it could be just a dirty connect. Start with the easiest repair and work to the hardest. It is never simple to find the problem you have to make the fix simple. Good Luck Rick

I found the temperature sending unit in the front of the engine behind the alternator bracket. It is hard to reach with normal wrenches. I was able to remove the alternator, which made it easier to see and remove. I bought a new unit, installed it, then connected it back up, and the gauge still stays on C. I thought maybe the gauge was faulty, so I found a good one, replaced it, but still can't get the gauge to move. Anyone got any other thoughts on what I need to look for? I am thinking I may have to buy an aftermarket gauge and mount it under the dash if I can't find out the problem here. Any ideas would be appreciated.

 

[captrick]

Try taking a wire and connect it to the temperature sender and run it into the car and connect it to the gauge on the none power side or ground. Make sure that the sender does not have anything on the threads it needs to have a good connection to the engine. The sensor measures the temperature thru a resistance to ground. With the wire hooked up to the gauge turn the key to run, it should read cold. Now start the engine and see if the gauge starts to read temperature. If it does then you have a bad wire or connection to the gauge from the sensor. Good luck Rick

 

[DEVIL DOG 62]

Where is the temperature sending unit on the 351M (400) engine? I've been told it is located on the back of the engine on the intake manifold but didn't find anything back there except for the oil sending unit. I saw what looked like one on the front of the engine behind the alternator which had a double connector on it. There are also two other things with vacuum fittings in the intake near the front of the engine. My temperature gauge will not move off C and I would like to get this working.

on my 390 it's right down on the front of the intake close to where the top radiator hose attach's to the thermostat housing. It has 1 wire on it

 

[Canon_Man]

Got a similar issue with the temp sensor in my Dad's '78 ...

Works until the coolant begins to reach operating temperature then drops to cold. Diagnostics tell me it's getting 5V and all the other gauges work so it's not the constant voltage regulator.

Thought the two prong connector might have been put on the wrong way, but it only goes on one way. The temp sensor controls when the AC comes on and only allows it to come on when the coolant reaches 115 F. There is a similar temp sensor available for the '76 T-bird with 460 V-8 but it doesn't have the vacuum connections.

I need to source one somewhere. Classiccars has one, but it doesn't look like the right one either. RockAuto - no got.

Wondering where the OP found a replacement. Anyone?