StuK

1988 L98.

No temp reading from the gauge on the engine. Oil reads normal. I believe the main radiator cooling fan is not coming on due to lack of signal from the CPU telling it that it's time. I am not familiar with American cars (sorry, mostly air cooled German convert to American stuff) so, is the water temp sender on the radiator or the block? If block, is it the lower end on the passenger side? I saw some kind of sending unit lacking a wired connection while I was changing the oil.

If I cannot get the main fan to function, what is the best way to rig the fan? toggle switch direct to battery? Should I use a relay to trip the juice to the fan motor? Is that relay next to the radiator on the drivers side the fan relay or is it the relay fwd of the battery?

I figured out it wasn't working when I got stuck in traffic last week and the oil temp got pretty toasty. I bought the car at the start of winter and had no issues while it was pretty cool outside.

Thanks fellas for input and experience!

rodj

Gauge and temp input to computer are from separate senders.
If engine is running correctly , the coolant temp sender (CTS ) for the computer ( at front of intake manifold ) is working and sending correct temp indication to the computer (ECM )
If it wasn't you would have engine operation problems

Faulty temp gauge is a different problem with the gauge / wiring / gauge sender between # 6 and 8 plugs

By batt
Most likely your problem is with the fan or wiring to it ; hotwire the fan and confirm fan motor works.
Then check for permanent 12V ( thick red or org ) at the relay , fusible link supplying relay may be blown
Bypass the relay and see if fan runs ; confirms wiring from batt to fan intact
Check fan fuse ( control side of relay ) check for 12V ; key on on thin ( blue ? ) wire @ relay
Ground the relay control wire ( green ? ) and see if the relay closes to run fan ; relay may be faulty

Control the relay via a switch
or use a standalone fan sending unit ( no switch required )
http://www.racerpartswholesale.com/p...n_Accessories2
like this of the working range you require

Cliff Harris

The ECM controls the fan based on the coolant temperature. You can test the fan and relay by jumpering pin A to B on the ALDL connector and turning on the ignition (don't start the car). The ALDL (Assembly Line Diagnostic Link) connector is above your right knee when you're sitting in the driver's seat.

The relay for the fan is mounted on the wheelwell below the master cylinder.

Here's a diagram of what the ALDL connector looks like:

StuK

Hey fellas, quick question on hotwiring the fan.

When I unplug the relay by the battery to check the function of the hot wire, I got 12v hot.

Question is: If I jumper the fat red hot wire with the relay unplugged to the fat black ground in the relay connection, should that kick on the fan? If so, it didn't.

Thanks again.

awsum87

The sensor is on the passenger side of the block. Between the sixth and eighth cylinders. If the wire isn't connect to the sensor your temp gauge in the car will just read LO. As for the coolant fan you can just connect the dark blue wire to the black/red. The fan should run when you turn the key to on position. If not the fan is no good

ccrazor

If you jumper a hot wire to ground you should blow a fuse!! If nothing happened you need to check the fuse that feeds the red wire..

StuK

I expected to get a spark so it was a quick tap... tap... No sound, no spark. The two connectors in the plugs for the red and black were both heat discolored. Not the two connectors for the smaller wires. I figured that jumping those might have closed the circuit kicking on the fan or at least sparking if I got it wrong? The red wire "is" hot still going from the "-" post on the battery to the red wire with a test light. Light lights! I was hoping to test the fan without taking a bunch of stuff off to get to the fan connection on the fan motor. Figured I could jump it at the relay plug? No?
Thanks for the reply CC.

ccrazor

Not sure of the wire colors on your relay socket as I have an 84. On mine I have a blk/red wire on the relay that goes to the fan, if you have a similar wire on your relay you should run the fan if you jumper from the large red wire to the blk/red wire. What are the other two wire color on the socket?? could the black wire be dark blue?? If it could be it should have 12v with the key on..

rodj

that would be a blk/red wire
Disconnect the plug out of fan motor and put 12V ( + ground ) there to see if fan actually works

Not exactly recommended to put the 3A relay control supply direct to the fan that draws 20A +

SunCr

f"I expected to get a spark so it was a quick tap... tap... No sound, no spark"

For your own safety, find someone else to work on your Vette, house, etc.

StuK

Well, I just pulled the fan out this evening and hot wired it to a spare battery I have in the garage.

Nada.

So, First things first. A buddy happens to have a fan from his parts car so, I am going to pick that up tomorrow after work.

I picked up a temperature sender which is not in yet. The dash gauge just reads "LO" and never shows a temp so, I am pretty sure I need to sort that as well.

Are the bulbs in the information control center easily replaceable and available at any chain store? I would like to jump the harness to get the codes but, the check engine light is out.

I paid my dough to go play with the Granbury Texas Vette Club at Texas Motorsports Ranch in two weeks so, I am on a tear to get my car where I think she needs to be to do that.

Thanks again for you help!

Stu

ps. No Worries SunCr.

The tapping wasn't to make a solid connection... it was just to listen for anything and check for current. The wire should only melt with current flowing enough to heat up the wire and that would take a solid connection. When I say tap tap it's like accidentally hitting ground with a hot wire. I'm sure we have all done that with no permanent damage except for a quick reaction to remove the offending touching!

Thanks for the concern!