I'm confused and would appreciate any advice on coolant sensor locations for my '86, alloy head.

At the front of the inlet manifold we have our 2-pin Thermo Time switch which controls the activation of the 9th cold start injector for 8 seconds AND the 2-pin ECM Coolant Sensor (yellow & black wires). No problem there. We also have the Low Coolant Sensor that plugs into the RHS of the radiator. No Issue.

BUT ... there are, of course, 2 further locations (between cylinders 1 & 3 and between 6 & 8) for coolant / engine temperature sensors. One is dedicated to feed the water temp gauge, the other is a switch which will activate cooling fan(s) at 227 degrees.

My problem is that I am trying to align the correct item in the correct location. And I don't trust the accuracy of the Shop Manual which seems to be a combination of transitions from 1985 to 1986

Also, the Shop Manual and other sources (eg Haymes) use different terminology throughout their pages for these sensors. The shop manual has a diagram at 8A -201-2 (Component location diagrams) which illustrates a sensor on the left side, but fails to label it. Illustrations on the right side, also fail to positively identify the sensor! So, I figured I would go to the circuit diagrams to look for wire colors .. 8A-82-1 has the IP (Instrument Panel) Coolant Temp Sensor color as blue but does not identify location. Cannot find any wire colors for the switch anywhere. Terminology is all over the place too .. I have seen "Engine Temp Sensor, IP Coolant Temp Sensor, Cooling Fan Switch, Water Temp Conn, etc. ALSO 1986+ models MAY have switched sides of the engine for these 2 sensors from 1985 models.

On my car the RHS (dipstick) has a single green wire, the LHS we have a yellow wire which exits a loom near the alternator, then, in the last few inches, splices into 2 - green and blue wires, into a 2-pin plug.. Go figure! I read somewhere that one of then sensors has a single wire and grounds itself on the engine (we must expose some bare thread to do this).

Engine Wiring section -
6D5-4 illustration labels the 'Cooling Fan Temperature SWITCH " on the RHS.
6D5-3 illustrates the "Water Temp Conn" on the LHS.

Hames manual says the "cooling fan SWITCH" is on the dipstick side, cylinders 6 & 8, 2 pin.

Can anyone provide clarity for a 1986 car PLEASE ... Wire colors would be great too.

 

The engine temp sensor (2 wires blk and yellow) in front of the intake next to the cold start switch is used by the ECM to calculate fuel mixture and for the ECM to turn the main fan on (at 226° on my 87)...

The main fan can also be turned on (via the ECM) by the AC pressure switch installed in the AC piping near the dipstick (on my 87 with HD cooling). Some cars with 2 fans are mounted side by side , I am unfamiliar with which condition controls which fan on these.

The temp sensor (grn wire) between cyl 6 & 8 is used to display temperature to the driver on the digital dash.

The HD fan sensor/switch (grn wire with wht stripe on my 87) between cyl 1 & 3 is for HD cooling (on cars with HD cooling such as Z51 Z52 and some other cooling packages) which turns the fan on that is in front of the radiator and / AC condenser. This fan faces the rear of the car and is not controlled by the ECM. It is only controlled by the sensor between cyl 1 & 3.

I test my rear facing HD fan by taking off the connector and grounding it.
Do you have a Z51 Z52 or an RPO code such as B4P ??

Ditch the haines manual and buy a $20 field service manual.
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@Vets-Vet OP has the FSM I'd say, All of his references are FSM notations.

 

Thanks @WVZR-1 ,

@GraemeR The schematic is from an 86 FSM. Keep in mind some owners liked to wire in switches on a second wire so they could turn this second fan on when they wanted. If so you may find an unknown switch somewhere near the driver. The HD fan relay on mine is mounted on the front top left corner of the radiator cover shroud on the drivers side.
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Appreciate those comments, and yes, FSM is at hand and studied thoroughly, hence the quotes to it in my post. Also I have a RPO code B4P ("Radiator cooling boost fan") and V01 (Heavy Duty Radiator"). Not sure if that changes any wiring configuration, but I doubt it. So I need to hook green wire to 6/8 sensor to display temp, and green/white stripe 1/3 for front fan. I think it was later years that saw twin main fans.

 

Are you able to tell whether these 2 sensors have 1 or 2 pin connectors? Seem to be single pin. The circuit routing you supplied will be of help - THANK YOU!

 

Until you prove the FSM incorrect I believe you rely on it. If you use 8A-82-1 & 8A-82-4(component location) in the FSM it states that the gage sender is on the left side(driver). In post#5 I believe you've assumed differently. If you look at 8A-82-1 & 8A-82-4 you'll see that mentioned. I can't verify for you the change of GRN to BLU (C164) but maybe another 1986 owner can verify for you. Trust 'ONLY' an '86 owner for verification.

 

The HD fan sensor is a bullet style round connector, the gage temp sensor is a single blade with spade connector. Both of these sensors go into the water jacket. If the wires were long enough you could put them on whatever side you wanted. Look at the HD fan relay, what color wire goes into it ???
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I'm not an 86 owner, but I understand the confusion the OP has regarding the temp senders and locations. Here's some hints, the way I understand these circuits in the years mentioned.

The B4P boost fan is a stand-alone fan controlled only by the temp switch in the cyl head. It is a green/white wire. In 1985 only this switch is on the Passenger Head between #6-#8. In 1986, the switch moves to the Driver head, between #1-#3. Still a green/wht wire.

In B4P configurations, there is no "over-ride" switch in either head for the main fan.

The Gauge Sender is in the Driver Head in 1985 only. In 1986, it moves to the Passenger head. The FSMs I have for the Atari Dash cars show a dk green wire all the way to the sender. (On LT1 cars, there is a short blue jumper wire from the sender down to a connector by the starter motor where it becomes the dk green wire that remains dk green all the way to the cluster. I have no idea if this 'blue wire' or connection exists on a 1986 L98.)

^^ 100% correct-o-mundo. ^^ (1990-up has twin main fans. No more B4P "pusher".)

 

Thanks Vets- Vet - Yes they would be inter-changable, and its a green/white wire that goes to the Fan Relay. Its that color at the relay, but some fool has changed it at some point on its journey from the sender. I am simply trying to get the right sensor in the correct hole based on the wiring that is in my car currently, (or SHOULD BE) and its B4P. I would gladly re-use the existing sensors, but the new Edelbrock heads have larger hole sizes, so new sensors of a larger thread would avoid me using adaptors. Thanks to you and others I think I have it sorted now. When engine is finally started we can do some tests.

 

Temperature sender for the gage would be a possible buy for the sender, that's a quite common find nearly anywhere. A switch for the B4P would require some research or maybe just the use of the correct bushing works to use OE.

 

On that gauge sender - does anyone have any clues whether it has 2 functions .. to (a) illuminate the red dash temp warning light at a predefined temp, and (b) to continually display the digital temperature reading? I made some enquiries to a well known sensor manufacturer & distributor and they advise that they don't make one that does both. Maybe the warning light is ECM controlled via the ECM temp sensor at the front of the inlet manifold. Also emailed Edelbrock (since its their heads) but no reply.

 

Gauge sender does 'only' the gauge - single purpose!

 

The red tattle-tale warnings are controlled by the cluster electronics based on the digital indication. All 4 of the functions in those two windows have out-of-range warnings annunciated by the Red Square.

An interesting feature is that if the display is on the other function, Ie the switch has Volts selected, but if there's a Coolant Overtemp, the display switches to Coolant Temp, and if dimmed goes to full brightness and illuminates the Red Square. All done by programming within the cluster.