i have an 87 442 all factory stock, I remove the stock 307 and installing a 350 Olds. I'm not using the factory carb or distrubutor. How can I bypass the computer to run my cruise and A\C??
computer by pass
- Thread starter tmaj1865
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The cruise control shouldn't be a problem. It doesn't talk to the computer. It DOES require the vehicle speed sensor input, which is on the back of the speedo. The VSS gets power from the computer fuse (ECM/DEC fuse), so if you've pulled that one, the cruise won't work.
The A/C is a little more of a problem. There is a green wire from the A/C switch to the computer, but this simply tells the computer that the A/C is turned on and to increase the idle speed. There is also a brown wire from the A/C compressor relay that is controlled by the computer. The computer disconnects the ground on this relay to turn off the compressor if it senses low freon pressure. This brown wire is in position 19 on computer connector C1. There is also a black wire in the same connector in position 15. This is the wire that tells the computer there is low freon pressure. By connecting the black wire (which is switched ground) to the brown wire, the compressor will work and the relay will automatically cut out when the freon pressure drops too low. Why you needed a computer in the middle of this is a mystery to me.
The A/C is a little more of a problem. There is a green wire from the A/C switch to the computer, but this simply tells the computer that the A/C is turned on and to increase the idle speed. There is also a brown wire from the A/C compressor relay that is controlled by the computer. The computer disconnects the ground on this relay to turn off the compressor if it senses low freon pressure. This brown wire is in position 19 on computer connector C1. There is also a black wire in the same connector in position 15. This is the wire that tells the computer there is low freon pressure. By connecting the black wire (which is switched ground) to the brown wire, the compressor will work and the relay will automatically cut out when the freon pressure drops too low. Why you needed a computer in the middle of this is a mystery to me.
What does the distributer have to do with it? The reason I ask is I replace the distributer about a month ago, and after that he A\C did not work. I put the old one back it and it worked. I did notice that the old distributer had an extra four wire plug. Whats up with that?
Thanks
Thanks
The computer uses the tach feed from the distributor to sense engine RPM. If you disconnect it, the computer assumes the engine is idling too slowly and shuts off the A/C to prevent the car from stalling.
You'll also need a non computer throttle kicker solenoid for your carb to bump the idle up when the A/C compressor is on. Simply connect the non computer solenoid positive wire to the positive wire of the A/C clutch to get it to function. On computerized carbs, the kicker solenoid is controlled by the computer.
-Mark-
-Mark-
Uncletruck said:
Actually, it depends on how the 350 is set up. 60s cars didn't need a throttle kicker solenoid. It wasn't until emissions controls came into effect in the 70s (no vac advance at idle, for example) that this was necessary.
I always thought the throttle kicker solenoid was to give the engine a little idle speed boost when the load from the A/C compressor is on. (I think it performed some other things on the CCC engines.) Couldn't this still be beneficial even if one were to use a 1960's engine, or did the added HP of those old engines without a lot of emissions equipment make it unnecessary?
-Mark-
-Mark-
Uncletruck said:
That's exactly right. Current engines are designed to bare minimums and so the added idle speed boost is necessary to prevent stalling. 60s vintage cars had excess performance (even at idle where emissions and economy were not a concern) and could absorb the drag of the compressor without the throttle kicker. As an aside, small motors (like my wife's Honda and my son's Corolla) actually adjust the idle speed to compensate for the added drag of the alternator when you step on the brakes or run the heater motor!
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