Dual station temp. guages

I'm not looking for pity so I'll eliminate the heartjerking stories, curses and*wasted time and money*of this week trying to get the same temp reading on my lower and upper helm.*

I know that first, I need a dual station sending unit.* I replaced the old one with a new Sierra dual station sender which is supposed to be compatable with the two new teleflex temp guages. hooked everything up and still get very different readings (both lower than the actual water temp). The signal wire checked out from the sender to the lower helm, and also from the lower helm to the upper helm.* The power supply wire tested good and also the ground to both stations. I installed bus bars to eliminate the daisy chain connections.

Today I bench tested the sender and new gauges using 180 degree water, good leads, good battery, good ground to the sender and gauges--nothing to chance--except the two gauges still read low*and inconsistant (120 and 150 and couldn't get them to go higher by raising the water temp).

The guy where I bought the stuff said only the sender had to be dual station and the gauges only had to be compatable to the sender (which he said they were).* Another guru in this field of wonderment said the gauges also had to be "dual station".* I looked at an assortment of gauges on the internet and couldn't find one that said "for dual station only".

What am I not understanding, or doing wrong?

I really appreciate your expertise, having taken it to heart several times since wading into the new world of trawlers.

Thanks, Geezer

*

*

geezer wrote:What am I not understanding, or doing wrong

Click to expand...

*Hard to say over the net but try this"* [url]http://tinyurl.com/3nr5bac[/url]

i think that the sender is not the right one,if you have atwin screw take one out of the other engine* and see what happens,* try it on one gauge and see if it works but it sure sounds like it the sender to me

RickB wrote:

Click to expand...

*Hard to say over the net but try this"* [url]http://tinyurl.com/3nr5bac[/url]

*Damn good suggestion! **

I just spent fifteen minutes reviewing this link and learned alot.

Thanks Rick, I haven't seen that webpage and it really has a lot of information.

I"m tending to agree with Jerry concerning the sender-the article seems to indicate a sender malfunction causing the gauges to read low.*

I'll let you know*what I find.* Geezer

*

*

My single-station Coot came with sensors for a dual-station boat.* Thus, oil pressure read 25 and water temperature 213.* The replacement*sensors show 50 and 180, respectively.

jleonard wrote:*... that mech gage is the one I have the most faith in.

Click to expand...

The only problem with mechanical temperature indicators mounted on the engine itself is they are very susceptible to vibration damage.

If you can find a capillary type thermometer and mount it off the engine you will get good results. If you mount a bimetal unit on the engine don't expect long life or accuracy.

I found another person with the exact same problem as I'm having- http://www.sailnet.com/forums/gear-maintenance/41670-impossible-trouble-dual-temp-gauges.html In fact, I could have written his inquiry. He is also using Teleflex gauges and a compatable sender. I'm seriously wondering if it's a problem with Teleflex?

Is anyone else using dual station sender and Teleflex gauges?
Geezer

Is it possible to remove the original sender, insert a matching "T", and then use two individual senders?

I'm not sure, but I believe my engine has a seperate sender for each gauge.

did you try using the new sender with one gauge to see how accurate it is??? i tryied using a t fitting one time long ago and it did not work

capt jerry wrote:
did you try using the new sender with one gauge to see how accurate it is??? i tryied using a t fitting one time long ago and it did not work

Click to expand...

*Funny you asked--I bought two new Datcon marine heavy duty matching temp gauges and a guarenteed compatable dual station sender from the electronic specialist in the area.

Took them to the bench, hooked them up correctly and heated the water to 185 F. both gauges registered the exact same--145 F.* I then unhooked the second gauge and presto, 185 F.* Took the sender in and asked them to make sure it was a dual station sender.* The order catalog and the company tech on the phone*confirmed*that it was indeed a dual station and was compatable with the gauges that was purchased.

Tomorrow they*are going in the boat to see how they register--just maybe the sender requires the engine block for a ground instead of a lead from a battery. (?)

I read that the sender had to be in the block with the water running around it. Guess when a tee is used the water is deadheaded and doesn't give an accurate reading. I do have a second water sender tap but it's being used for the high temp alarm--really hate to lose that.

I'll let you know what happens-thanks for all the input.

Geezer

"Guess when a tee is used the water is deadheaded and doesn't give an accurate reading. "

Water is quite a good conductor of heat.

Perhaps for your instant overheat alarm a T might slow down the accuracy.

But on a simple gauge I doubt you could notice any delay.

Here's a pretty good article from Teleflex regarding troubleshooting the system:

http://www.jamestowndistributors.com/userportal/document.do?docId=842&title=Troubleshooting+Teleflex+Water+Temperature+Gauges

Couple of good points:

Use an ohmmeter to test the sender at various water temperatures.

If there's thread sealant on the sender, its grounding may be compromised.

Ideally you should use a separate ground wire directly to the engine from the instrument that doesn't connect to anything else at the panel (except possibly ground for the oil pressure).* Any ground voltage differential between the panel and the engine will result in erroneous readings.

I installed the new Datcon Temp gauges and the new sender in the boat and now both the upper and lower helm read 180 when the engine is warmed. Why it read differently on the bench is a mystery that I may never solve. One problem was the limited space between the block and the expansion tank on the 120 Ford Lehman, where they decided to put the tapping for the sending unit. The new sender has the signal terminal pointing streight up with a threaded stud (unlike the original which was is bent at a 90 with a spade connection).
I made a thick plastic gasket to fit between the block and expansion tank and put a gasket on each side to increase the space, also cut the excess brass stud off the sender and put piece of rubber material between the sender and the expansion tank to eliminate any chance of it shorting out on the tank. I learned enough about guages the last few week to keep me happy for quite a while. Thanks for all the suggestions.
Geezer