Center Gauge Malfunction. Temp Gauge

[1972GT-351]

Hoping there are some electrical pro's that can answer this one for me. I will keep it as short and to the point as I can.

The factory temp gauge has only worked about 5-10% of the time in the last two years. Here is what I have done so far.

- Changed the temp sender

- New wiring harness from the senders to the fire wall.

-Tried a spare set of gauges

-Grounded the temp lead and the gauge will go quickly to full hot. (from what I have read that means that the wiring, instrument voltage   regulator and gauge are good)

- Around 5.5V behind the gauge and 0.5v at the sender.

-I am wondering if my new sender is bad or not grounded correctly. So I purchases two new Motorcraft Senders. One has a green insulator   around the post  SW-2328 and one has a red insulator SW-925. See the picture.

So which one should I put in? This is my Mexican 1972 GT-351 with a factory 351W.

What other tests should I preform?

Any thing else need to be replaced?

Thanks in advance for the advice

Rich

 

[TheRktmn]

Hmmmm...

That F1SZ-10884-A is a 1991 Ford part that is supposed to have replaced the D0ZZ-10884-A (SW-925) and the SW-924 (Ford # D0WY-10884-A) for the 71-73 351 C or W with gauge.

It shouldn't make any difference, but I would install the 1970 P/N D0ZZ-10884-A.

You've verified the gauge and circuit to the sender, I can't think of anything else BUT the sender.

 

[midlife]

Are you using Teflon tape by any chance? That can kill the grounding scheme at the sending unit itself. Slightly crimp he 90* slip-on connector so it is tight.

Now then...here's the tricky part. Sometimes connectors and wires will show good voltage but won't work as the wire is internally broken and won't pass current. Have you replaced the engine gauge harness? They usually go bad due to the exposure to engine heat and the elements.

Finally, grab each molded connector for the temp sending line and tug moderately hard on the wire away from the molded connector. Sometimes that re-sets the wire crimp inside the molded connector and allows for a better signal. You should have 5.5-6.5 V at the sending unit line. You say it is only 0.5V. That tells me that there is some internal resistance from the gauge out to the sending unit itself.

 

[1972GT-351]

Hmmmm...

That F1SZ-10884-A is a 1991 Ford part that is supposed to have replaced the D0ZZ-10884-A (SW-925) and the SW-924 (Ford # D0WY-10884-A)  for the 71-73  351 C or W with gauge.

It shouldn't make any difference, but I would install the 1970 P/N D0ZZ-10884-A.

You've verified the gauge and circuit to the sender, I can't think of anything else BUT the sender.

Thank you Bob.  I will start with that and hope for the best.

 

[1972GT-351]

Midlife.

Great suggestions. I will look into the connectors. No Teflon tape. Just the red stuff that's on the sender. Does the red stuff mess up the grounding of the sender at times?

 

[midlife]

I have no idea.

 

[secluff]

Rich, There was so much confusion in the catalogs on these temp senders no one had any ideal what to use. The DOZZ (SW-925) and the DOWY (SW-924) were both for temp gauge applications depending on engine size. Problem is from the mid 70's until recently these two numbers  stayed in the system by constantly replacing each other. One year the DOZZ would be replaced by the DOWY, next year the DOWY would be reinstated and the DOZZ discontinued. The latest info from Ford shows both  DOZZ and DOWY discontinued and replaced by the F1SZ-10884-A (SW-2328). But the D0ZZ-B (SW-925) is still available and is in stock in large numbers at the Ford parts depots. SW-925 is the part# I've used on my cars with temp gauges which included 351C and W and a 429CJ. The sealant on the threads is Ford spec and will not hurt the grounding of the sender.

 

[will e]

When you say it only worked 5% to 10% of the time can you describe what not working is?

Any issues with the oil or gas gauge?

At the sender, are you using the factory push on connector?

 

[1972GT-351]

When you say it only worked 5% to 10% of the time can you describe what not working is?

Any issues with the oil or gas gauge?

At the sender, are you using the factory push on connector?

So the gauge stays at the full cold power off indication consistently. Then once in a blue moon it will come to life and give a good reading then go back to the off/full cold position. This is with both the original gauge and under the hood wiring and my spare gauge and reproduction under the hood wiring. All factory connectors. 

Both the oil and gas gauges work fine.

Thanks Will E

Secluff

That is a blizzard of inconsistency from Ford for sure. I will start with the SW-925 and see what happens

Thanks

 

[will e]

My guess is the factory gauge fitting and repro wiring isn't getting a good connection on the sensor. You don't have the issue when you 'ground' it since you know it is grounded. Does the connection feel a little loose? With the car warm and the ignition on try squeezing or pressing the connection sideways to ensure a good connection. Have someone watch the gauge while you do this (or video with your phone, or set up a mirror...)

 

[1972GT-351]

My guess is the factory gauge fitting and repro wiring isn't getting a good connection on the sensor.   You don't have the issue when you 'ground' it since you know it is grounded. Does the connection feel a little loose?    With the car warm and the ignition on try squeezing or pressing the connection sideways to ensure a good connection.  Have someone watch the gauge while you do this (or video with your phone, or set up a mirror...)

Thanks.

Sounds like I may get this figured out this weekend.

 

[1972GT-351]

Well now for the rest of the story, after a new underhood wiring harness, pulled the dash apart, swapping center  gauges , ground checks and tests, I went ahead and threw in a second new temp sender. Success!!

Now to put the interior back together again......

Once again I think I was bit by the cheep Chinese parts from CJ's. Last time was the condenser from there tune up kit that left me stranded after the second day it was in. Only Mototcraft or US made parts for me from now on.

Thanks again for all the help folks

TheRKTMN

Midlife

Secluff

Will e.....