Temperature Gauges

[Dragonten]

I just installed two new Stewart Warner temperature gauges on the upper and lower helm with new dual station sender on the engine. Both gauges are reading about 30 degrees too high. I know this because I checked with a temperature gun. I put high temp thread sealer on the sender threads. Could this be causing the inaccurate reading? I read older threads that said one should not use thread sealer on the sender. Just wanted to double check if this is correct and if others have had this same problem.

Thanks,

 

[SKYCHENEY]

Try to put an ohm meter from metal on the gauge to the engine block and see if there is any resistance. That should tell you if that thread sealant is inhibiting a good ground, but I doubt that's the problem.

 

[SEVEN]

You mentioned 30 degrees. What temperature did it used to show and what is it showing now?

 

[Captain Ralph]

New temp low or high?
Do you still have your old senders?
May have to work backwards on this issue.
I don't think the sealant is an issue.

There is still so much confusion about multi gauge senders.
VDO/SW specs further will test the best of minds..

 

[Dragonten]

The old senders were AC Delco and the gauges did work so can't really do any swapping. My other temp gauge in the engine room is electric (different brand as well) reads 160 degrees which is the correct temperature. My only other thought is they sold me the wrong sender.

 

[Dragonten]

Meant to say the old gauges did not work.

 

[Captain Ralph]

The old senders were AC Delco and the gauges did work so can't really do any swapping. My other temp gauge in the engine room is electric (different brand as well) reads 160 degrees which is the correct temperature. My only other thought is they sold me the wrong sender.

So, do you still have the old senders? Or part number read off of them?
I found your original comment, "reads to high."
In true SW mode, this means not enough resistance on the signal wire // sender..

 

[Dragonten]

I have the old sender but it is AC Delco not a Stewart Warner as the new gauges are. Also not sure if the old sender works or not. What would be the cause of resitance problem?Thanks,

 

[jim rosenthal]

It sounds like what you might call a resistance mismatch between the gauges and sender. Isspro Inc make a lot of senders, you might look it up with them.

 

[Lmcruiser]

You have to have senders designed for dual station. If you use the sender for a single station the gauges read high. I had this happen with a boat I bought and went to a lot of effort to fix until I tried a mechanical gauge in one engine and temp was normal. Called instrument company and got an engineer to explain. Bought two dual station senders and problem was fixed.

 

[Captain Ralph]

I have the old sender but it is AC Delco not a Stewart Warner as the new gauges are. Also not sure if the old sender works or not. What would be the cause of resitance problem?Thanks,

There are two ways for electric gauges to work. SW compatibility or VDO compatibility.
Gauge scales move based on low to high resistance (SW) or high to low resistance (VDO).
Now for dual gauges, since the meter/gauges them selves are just reading the resistance on the signal wire AND each meter/gauge on that wire affects the resistance on that wire, things can change the display quickly.
Proper part matching is important.

AC Delco and SW work the same. You could easily experiment starting here.


Funny thing, VDO makes SW cap equipment.

 

[Dragonten]

So sounds like I might have the wrong sender. I was led to believe SW gauges required SW senders and would not work with AC Delco senders. Or I could have been sold a single station sender by mistake. In any case, the first thing I will try is the old sender and see what happens.

Thanks,

 

[jim rosenthal]

Ralph summed it up. The gauges don't know the brand name of the sender, but they DO know the resistance and how much current they are seeing.

 

[SKYCHENEY]

I doubt the AC senders will work. When I changed out my oil pressure gauges, the AC senders did not work but the dual station SW senders worked fine.

 

[Dragonten]

It seems I had the wrong sender. I replaced it and appears to be working correctly.Mark

 

[jim rosenthal]

Good to know.

 

[Captain Ralph]

It seems I had the wrong sender. I replaced it and appears to be working correctly.Mark

Replaced it with a new or your original. If you can, post all working part numbers for us. I'm sure it will test us again, again, ,,..