faulty temperature senders

[John Mauser]

I have purchased 2 new temperature senders for my Volvo Penta 4.3GL-D from different suppliers and both of them read "no continuity, 0.L" when tested from the terminal to the body (ground) with a digital ohm meter. Even when heated there is no resistance provided. My temp gage manuf says it should be 400 ohm at 100 degF and 99 ohm at 175 degF. Has any one else had problems with faulty new senders (Sierra Part 18-7647)? Or am I doing something wrong in measuring them?

 

[alldodge]

What is the part number your bought?

 

[John Mauser]

What is the part number your bought?

Sierra 18-7647 which is supposed to be a replacement for Volvo Penta Part 872066

 

[Bondo]

I have purchased 2 new temperature senders for my Volvo Penta 4.3GL-D from different suppliers and both of them read "no continuity, 0.L" when tested from the terminal to the body (ground) with a digital ohm meter. Even when heated there is no resistance provided. My temp gage manuf says it should be 400 ohm at 100 degF and 99 ohm at 175 degF. Has any one else had problems with faulty new senders (Sierra Part 18-7647)? Or am I doing something wrong in measuring them?

Ayuh,.... Welcome Aboard,...... Is the t-stat housing properly grounded,..??

 

[John Mauser]

Ayuh,.... Welcome Aboard,...... Is the t-stat housing properly grounded,..??

I believe the Tstat is grounded. But the ohm reading across the sender is the same whether I test it in the Tstat or out of the Tstat. The sender has no resistance no matter what I do to test it. This sender is no longer available at Volvo Penta, so had to buy after-market. The ones I bought are made in Mexico, probably by the same company.
Where can I buy a part that can be expected to work?

 

[alldodge]

Sorry missed you put part number in first post
Looking up Sierra and mallory and unable to find specs

I am unable to verify that the part number is a gauge sender or a temp switch. Put it in a pan of water and get the water up to a boil to see if it goes to zero ohms

 

[John Mauser]

Sorry missed you put part number in first post
Looking up Sierra and mallory and unable to find specs

I am unable to verify that the part number is a gauge sender or a temp switch. Put it in a pan of water and get the water up to a boil to see if it goes to zero ohms

I tried the heating in a pan of water. Resistance still shows 0.L on digital ohm meter indicating it is an open circuit - no continuity.

 

[John Mauser]

I tried the heating in a pan of water. Resistance still shows 0.L on digital ohm meter indicating it is an open circuit - no continuity.

I am wondering if I am testing the temperature switch rather than the temp sensor. By showing "no continuty" at temps below about 250 makes me think it is the switch. However the repair manual says the sensor (sending unit) is usually located in the Tstat housing which is the one I have been testing. Is there a possibility that the switch is actually in the Tstat housing and the sensor is on the exhaust manifold or elsewhere?
Hopefully someone with better knowledge of the 4.3GL-D could answer this question.

 

[alldodge]

Do think its the switch and temps need to get up above 200*
All the switches have a Tan/Black wire
The sender has a Tan wire and looks like it has a stud with a nut connection. On Mers they are both on the thermostat housing. Look on the intake

 

[John Mauser]

Do think its the switch and temps need to get up above 200*
All the switches have a Tan/Black wire
The sender has a Tan wire and looks like it has a stud with a nut connection. On Mers they are both on the thermostat housing. Look on the intake

View attachment 345495

Thanks for the input. I will check it out and let you know.