5.7 Temperature Sender

Good Evening,

I have a 1994 Mercruiser 5.7 (serial # 0f0......) with a 4 barrel webber and an alpha 1 (gen 2). I just replaced the thermostat housing to a design #1. When I got the boat started, i noticed that my temperature gauge wasn't working. I grounded the connection to the gauge and the gauge pegged hot. I tested the resistance of the sender and it came back 0. I tested the resistance in the audible alarm sender and that appeared to be working. Be jumping that sender to the gauge wiring, it appeared to work. My question is, which sender do i use. I'm not sure if it's a 3/8 or 1/2 and am not sure about the dual part that I see for sender options. Also, do both senders work on the same resistance to show temperature. Thanks in advance!

Marc

Re: 5.7 Temperature Sender

One of the sensors is a switch (for the alarm) and is just on and off. The other is the sender for the gauge and runs between 33 ohms and 240 ohms for driving the gauge. When you put the new thermostat housing in, did you use the genuine gaskets? If you didn't, then that could well be your problem. The genuine gaskets have a couple of brass eyelets in them for continuity... Specifically for the gauge...

Chris........

Re: 5.7 Temperature Sender

Thanks Chris. I did use the gaskets provided. I checked the resistance in the alarm sender and i got proper OHM's and when jumped to the gauge connector, the gauge then worked. I did use teflon tape on both senders and wonder if that has something to do with it.

Thanks
Marc

Re: 5.7 Temperature Sender

The book says you shouldn't use teflon tape on the senders. I've never had a problem. There is enough metal to metal contact in the threads as it bites through the tape to complete the circuit.... But we are 'by the book' here, so I have to tell you that you should remove the senders and put a liquid thread sealer, like Loctite 567, on them and re-install them....

Chris.......

Re: 5.7 Temperature Sender

Thanks for the help Chris. Makes sense to me!

achris said:

Re: 5.7 Temperature Sender

One of the sensors is a switch (for the alarm) and is just on and off. The other is the sender for the gauge and runs between 33 ohms and 240 ohms for driving the gauge. When you put the new thermostat housing in, did you use the genuine gaskets? If you didn't, then that could well be your problem. The genuine gaskets have a couple of brass eyelets in them for continuity... Specifically for the gauge...

Chris........

Click to expand...

Chris.
Question on the senders. can bot be the same type (806490T) asking because i notice that one has a black piece on the top of it while the other with the 2 wires does not.