i bought the car today.
2500.00 for a vette was a good deal.
now i have a few problems.
the haynes manual i have says the cooling fan temp sensor is in the right head behind the dipstick.there is no sensor there nor is there a harness for 1.
the sensor i found is in the left head just behind #1 cylinder,again no harness.the cooling fan is not working. what color wire should i be looking for to hook to the fan sensor?
after running a few min the car surges and the ses light comes on.
i cant pull any codes thru the adal .
the tach is inop because its not hooked up.i have a purple looking wire that connects into a kind of tan looking wire,(is this the tach wire?)
the engine runs a little rough,but half of the plug wires are loose on the cap and the timing is off, but engine hold 63psi of oil pressure.
the gauge in the dash shows coolant temp as low,it never said anything else,but i know the engine was getting hot.

 

The Haynes manual can be inaccurate because it rolls all year C4's (except ZR1) into one book. You have to dig and short through the info that does not apply and is sometimes inaccurate on the small little changes from year to year. Get the GM shop manual (Helms) for your specific year instead. The wiring diagrams alone are worth $100 and everything will be specific to your year.

So you have inoperable fans and temp guage hu?

To clarify. There are either one or two "sensors" on your car's heads depending if you got one cooling fan or two. One is a coolant temp guage sender that sends the temp reading to your instrument cluster (it's on the passenger head near dipstick on my '86) that they all have regardless of single or dual fan configuration pictured below. It has a single spade type connector with a single green wire. If you have dual cooling fans, there will also be a cooling fan switch (sensor) with a round type connector with single wire on the other head between two of the spark plugs. If only a single fan car, there is no fan switch on the other head and instead a pipe plug with a square hole in it's place with no wire.

This is the coolant temp guage sender. On my '86 it's on the passenger head.


Yours either only needs to be plugged back in (find the wire), and/or replaced with a new one. Trace the harness and find the wire, plug it in, and see if the guage works propertly now. If not, then replace the sensor with a new one. This is why your cluster temp guage does not work.

Check the cooling fan relay:



Unplug the relay, and connect a wire between the outer left and outer right terminals of the connector with key on and motor off. This gives direct current to the fan bypassing the relay. It simulates the relay in the closed position which happenes at about 230 degrees. If the fan runs, the fan is good. The relay is probably not closing.

Or

Bend a paperclip into a U shape and insert it between the two upper right hand terminals (A and B) of the ALDL connector. Then turn the key on with motor off. The fans should run and stay on untill you remove the clip or switch the key off. At the same time, the engine light will be flashing you your trouble codes.

 

Why not?

http://corvettebuyers.com/c4vettes/ecm.htm

 

Nice post 86PACER. This pretty much answers the original post. I can't really add to this.

 

Except thats not the CTS for the fan, thats for the gauge..

The fan runs off a cts with a plug in style connector, looks kinda like a knock sensor. On my '87 I think it was in the right head, the gauge in the left, and there should be an additional CTS connector also in the front of the intake, with a plug that looks like an IAT that the computer will use as a fail-safe if the original CTS fails the ECM will kick the fan on at like 240.

-- Joe

 

Again that depends if you have one or two fans. Except in 85, single fan cars don't have one. It's plugged off. The cooling fan relay cycles the main fan on and off with no fan switch on the head.

Indeed, the aux fan switch uses the exact same type connector as does the knock sensor.

 

The coolant temp guage sender is between #6 and #8 spark plugs in the passenger side cylinder head. All it does is send signal for temp readings on the dash. Single green wire.

The CTS in the front of the intake manifold sends resistance signal to the ECM (yellow and black wire). From that information the ECM can turn the main fan on and off according to the reading in the chip. The CTS is right next to the CSV temp switch which should not be confused (injector type connector with a purple and tan wire).

The aux fan is grounded when recieved the proper signal from the temp switch between #1 and #3 spark plugs in the drivers side head (~238*). Single green wire.

 

The CTS in the front is just a fail safe though. If you look at the fan enable constants in the chip, they are about 10degrees higher than when the actual fan switch turns the fan on. (at least thats how my '87 is, and all the fbody's I owned before). Right now, I have that fan switch removed, and I'm using the chip to turn on fans.

Now that I think about it, you are correct, gauge is on the right and sender on left in the y-body, cuz when I installed my engine I had the sensors setup f-body style (gauge left, sender right) and had to switch them after the motor was in the car..

-- Joe

 

Lots of info here already, so I'll add some reading material.
http://members.shaw.ca/corvette86/Co...0View%2086.pdf
http://members.shaw.ca/corvette86/Co...%20Control.pdf
http://members.shaw.ca/corvette86/No...it%20Check.pdf

 

That just isn't correct. The engine coolant temperature (ECT) sensor, in the front of the intake manifold is the only source of coolant temp information for the ECM. The ECM adjusts the fuel mixture, sets the idle speed, and makes other decisions based on the engine temp as reported by that sensor. Also, with that sensor input, the ECM controls the main fan.

The cylinder heads are the same, left and right. The threaded holes in the water jacket is the same for either the left and right heads. When a head is on the right side of the engine the hole is between, and slightly above, the #6 and #8 spark plugs. For both the 1986 and '87 C4s, that is the location of the IP (instrument panel) temp gauge sending unit. On the left side that hole is falls between the #1 and #3 plugs, and again, for 1986 and '87 (it DID vary in some years) that was the location of the auxiliary fan SWITCH, if the car has the B4P option.

Great job, 86PACER. That is a super write up and pictures. Too bad, the unknowing had to pipe up and cast doubt on it.

 

No kidding, my point was, it doesn't control the fan temp unless the other sender dies, making it a FAIL SAFE.. For the application of the fan, that sensor is not primary but a FAIL SAFE.

IF you look at the wiring diagram, and the fan constants in the bin, you'll see that its SECONDARY to what the sender enables the relay at.

-- Joe

 

I can't comment on '85, Only the one I have. '87. Though '85 appears to be wired way differently than mine.

-- Joe

 

ses light does not come on with the key on.
i have tried jumping a&b.nothing happens.
there is no sensor in the right head.
the only green wires are going to the a/c system and the sensor in the radiator.
the charts agent 86 posted tell me to see chart a1.
can someone show me chart a1.
i will post pics when i find out how.

 

And as I said, that is not correct. The ONLY signal to run the main fan comes from the ECM. The ECM can activate the fan, based on engine temperature (from the sensor in the front of the manifold) or A/C system pressure. There is no "other sender". The fan temps programed into the ECM are a back up to nothing. The manifold mounted sensor and the ECM are the only temperature activation for the main fan. The main fan has no connection with the aux fan switch, at any time. In the 1985, ONLY, without an auxiliary fan, ONLY, there is a fan SWITCH, that backs up the ECM/ECT sensor team.



What sender??? There is no sender that enables the relay for the main fan. Post your wiring diagram. And explain it. I'm sorry, but you are incorrect.

 

It sounds like you have one heck of a mess, there. You are going to need the Factory Service Manual (FSM) that is published by Helm Inc. Sometimes you can find them for sale in the forum C4 Parts/Wanted section or on eBay. Or go direct to purchase your own, new, manual at www.helminc.com.

 

Take the DIC out of the dash and check the bulb for the SES light. It could be out or someone took it out because it was on all the time and they didn't know why and got tired of seeing it. There should be a coolant temp sender for the dash gauge between #6 and #8 spark plugs, or at least there was stock.

I know nothing of the coolant temp sender between #6 and #8 doing anything except sending dash information. If it's a bad connection, bad sender, or bad wiring the dash gauge will read LOW all the time.

 

Where abouts does it say see chart A1, it will help me find it if I knew.

 

I totally agree

 

http://store.summitracing.com/partde...view=32&N=700+

^^ this sender

I'll scan the schematic tomorrow, my books are at the shop.

-- Joe

 

If you were to use that switch, it would replace the aux fan switch and could be tied into the main fan relay also. From factory, only the ECM controls the MAIN fan. http://members.shaw.ca/corvette86/Co...%20Control.pdf