Brocksdad1

Hi name is Bryce
I just finished a install of a 89 vetted engine into my 83 k10. All Chevy harness. Everything is working great with exception to the single cooling fan is coming on and staying on as soon as I start the truck
Has new coolant temp switch and sender.
Solus pro says fan isn't being called. But the AC is on.

Im not using the AC at the moment but will in the future.

I won't be using the vetted harness ill be using the truck harness.

Could it be that the comp is turning on the fan because the AC is sensed to be on?

How can this be dealt with. Any and all help is appreciated

Cliff Harris

There is a switch in the high pressure A/C line that tells the ECM that the A/C is on. If that switch connector is unplugged the ECM will think that the A/C is running and the ECM will turn on the fan. You can put a jumper in the connector to fix this.

Brocksdad1

I have found two switches on the high side line that I saved off the car. One is a smaller round Grey pin type connector the other is larger black rubber ad type.

The Grey one when plunges in seems to cause me engine to ramp up a few rpm. But the fan stays on.

No change with the other

Thanks again for all input

WVZR-1

You've used the '89 cooling fan relay and it's wired "as intended" originally? An '89 would have possibly had an AUX fan also that would have been controlled by a different switch, relay etc. Did your donor have that option?

Perhaps it's an issue unrelated to the AC at all.

If you're using the '89 ECM as a "engine control" unit ONLY and have none of the '89 AC components in the truck it seems you've only a need to sort just the run components.

An ECM wiring scheme should be readily available I'd think in many places and you just choose the one you feel more reliable when comparing to an '89 wiring diagram.

Do you have reliable '89 wiring diagrams?

WHERE ARE YOU LOCATED?

Brocksdad1

The car did not have the aux fan I am sure of that.

The weird thing about this car is the wiring .Possibly a split year? I'm sorry if I get something wrong here I'm out of town.
The injection wires are prpl and blk and the other color .
I'm thinking that 89 is different .
The color on the coolant temperature switch on the intake is yellow and black .
When I completed the wiring on the truck I had a dealer service manual for a 87 and all wiring matches .
The car said 08/88 so would that not be a 89?
Anyway I'm stuck and appreciative of all help .
I don't have a 89 diagram .

I'm in Evansville Indiana .
I'm just down from Tabor Touch corvette parts .

WVZR-1

In this link there's ECM wiring for '87 - '89 and I believe they're very similar as implied in these diagrams but you could sort it through and use it as guide I believe. Just above the '87 - '89 there's a link to these in a .pdf that you could save/print or what ever with.

https://wiki.bentleypublishers.com/p...ageId=17989640

These should help you immensely and it might make it much easier to ask questions later based on what you find. Only be concerned with the "make run" aspects of the ECM and however you elect to control the other aspects of the build should have no bearing on what's done here.

I haven't ever verified what's mentioned here but a couple quick comparisons of what's mentioned seems pretty much correct. No guarantees!!

Good luck.

Brocksdad1

Thank you for the schematics

I'm in Cincinnati for work .I'll check out a few things and post my finds

Thanks again .