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Installed sensor module in Thunderbolt IV distributor

T

torbau

Member
I ordered a new sensor module for 1988 260 Mercruiser 5.7L. The replacement unit doesn't look anything like the original. It has wires instead of terminals. How is this unit installed? No instructions were received with the new unit. Has anyone replaced this module and if so how was it done?
 
what part number did you order?

The OEM replacement usually has the pigtail adapters to complete the installation...
 
the pigtails only fit the wires from the new sensor one way due to the bullet connectors. make those connections. Then slide the sleeves over the ring terminals on the ends of the pigtails... match the wires up (WHT-GRN to WHT-GRN, etc) to the old harness and use the short nut and screw to connect a pair. Slide the sleeves over the nuts and screw to insulate them...I cant remember if the sleeves are heat shrinkable or not - its been a while...and then connect the black wire to a good engine ground.
 
If the sensor is the original type, it has two phillips head screws which are loosened from the inside and thread into housing.
 
the blue wire if the sensor was a OEM Mercruiser part would be BLACK.
That wire should have a ring terminal and it gets connected to a ground stud on back of engine.
 
kghost said:
the blue wire if the sensor was a OEM Mercruiser part would be BLACK.
That wire should have a ring terminal and it gets connected to a ground stud on back of engine.
Click to expand...
There is a black wire from the sensor I know this is a ground wire. This blue wire is from the engine and was on one of the original terminals on the sensor . I don't know if it should connect to the wht/red or wht grn
 
That wire is not original,

Can you follow it and report back where it goes?

It may be the shift interuptor wire and may have been replaced with blue at some point in the past
 
kghost said:
That wire is not original,

Can you follow it and report back where it goes?

It may be the shift interuptor wire and may have been replaced with blue at some point in the past
Click to expand...
It actually runs to a ground on the exhaust manifold where the Thunderbolt module sits
 
torbau said:
It actually runs to a ground on the exhaust manifold where the Thunderbolt module sits
Click to expand...
I now think it may have come off of the bottom of the distributor when I removed the screw that held down the original sensor. Probably a ground to the sensor.
 
Remove that wire.

They may have used it as a ground for the sensor in the past.... use the black wire and connect to STUD on back of block. There should be one on each side and the Neg battery cable will be attached to the stud closest to battery. If No stud find the threaded hole if no bolt/stud in it and get a bolt 3/8-16 x 1" and use that.
 
kghost said:
Remove that wire.

They may have used it as a ground for the sensor in the past.... use the black wire and connect to STUD on back of block. There should be one on each side and the Neg battery cable will be attached to the stud closest to battery. If No stud find the threaded hole if no bolt/stud in it and get a bolt 3/8-16 x 1" and use that.
Click to expand...
It works now. Guess that ground fell off the distributor and I didn't notice it.
 
They may have added it to an older aensor assembly that did NOT have the black gdound wire, which they did not have for many years. There may have been a tech bulliten saying to do this.

There were many issues with the older sensors and I believe grounding the sensors grounds with a dedicated ground wire vs depending on the distributor housing as possible ground didnt work so well.

Thus the dedicated ground wire.
 
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