Brake Proportioning Valve Wiring

[coop34]

Does the wire from the proportioning valve go straight to the ignition switch and then to the dash cluster, or vice versa? I've seen forum posts describing both ways.

Also, i have TBI and would like to use the open #5 slot in the dash cluster for a SES check engine light. Would this need to be wired through the ignition switch as well? Or would I just go straight from the computer to the dash cluster?

Thanks for your help. Wiring is not my specialty.

[coop34]

No wiring gurus on today?

[coop34]

Maybe the Tuesday crowd can help me out with this?

[Stocker]

From the Electrical forum, maybe this will help: http://67-72chevytrucks.com/vboard/s...d.php?t=185856

Look at post #2 and click the "largest version" link. Brake warning lamp is at bottom center.

[VetteVet]

Originally Posted by coop34

Does the wire from the proportioning valve go straight to the ignition switch and then to the dash cluster, or vice versa? I've seen forum posts describing both ways.

Also, i have TBI and would like to use the open #5 slot in the dash cluster for a SES check engine light. Would this need to be wired through the ignition switch as well? Or would I just go straight from the computer to the dash cluster?

Thanks for your help. Wiring is not my specialty.

Well well no replies yet except for Stocker. I have been following your thread since you posted it and I think I know why no one has replied.
You haven't given any information that anyone can use to help answer your questions. We're not telepathic so you have to tell us what we are dealing with. You need to make a signature with this information in it as a minimum.
Year of truck, engine, transmission, special stuff like TBI, fuel injection etc.
You don't have to list everything just the main stuff. See some of the other posters to view examples.

Here is what your thread should have said.

" Hello my name is Coop34 and I have a 1970 Chevy pickup with a 5.7 liter engine out of a 1990 suburban. It has TBI with a 4l60 automatic transmission. It has a three hole dash with a temperature light. and a brake warning light. My question is."

How am I doing?

If you had this stuff in your signature you wouldn't have to write it all out in every post you make. Not only that but I wouldn't have had to spend 30 minutes searching your posts to find out all the information that I posted above.

Now here are the answers you are looking for.

On 67 to 72 trucks the brake warning light and the temperature light are wired to the ignition switch and to the lights. It does not matter if the wires go to the key switch first or to the lights first as long as they go to both. The best way to do it is to run a wire from the sender to the key switch and then run another wire from the key switch to the bulb. That way you don't have two wires on the cluster connector.

The key switch has a special terminal in it that grounds the two wires for the lights while the key switch is in the start position. The reason for this is just to check the light bulb by grounding the sending wire. Brown for the warning light and green for the temp light.

The key switch is on top of the diagram. The right edge of it shows the two green and two brown wires. They may be tan not brown.




The second question leads me to believe that you have changed to a seven hole gauge dash, because of the desire to use no. 5 on the cluster plug for the SES light. You could have the gauge cluster without the temp light and if so you would't have the green wire to the key switch.The no.5 terminal is used on the idiot light cluster and not on the seven hole cluster.

I did some searching and the SES light is turned on by the PCM or ECM whenever it gets a code signal from one of the sensors. It does that by just sending a grounding circuit to the light. The hot wire for the light can be any key on power source, but the temperature light socket is ideal for this as the diagram below shows. I can not say which wire from the PCM is the grounding wire for the light. If I had a schematic I might be able to figure it out. What year is the PCM from? The 90 burb?



The purple wire is the power wire and the no. 5 terminal will provide the grounding side from the PCM. I don't guarantee any of this so do it at your own risk. VV

[coop34]

Thanks Vette. When you started mentioning that I had a 5.7L out of a 1990 Chevy, etc., I thought you might be telepathic! Thanks for taking the time to research the answer for me. Sorry, I didn't give enough information. I thought that since I posted the question in the 67-72 section of the forum, that folks would know that my truck was from this era. I assumed it was a general question I was asking. My bad.

I actually have the 7 gauge dash. I should be able to finish up the wiring for the brake warning light now thanks to your suggestions. Thank you!

As far as the SES goes, the PCM comes from the 1990 Chevy donor truck, and I have a new harness from fuelinjectionconnection.com. There is a wire labeled SES, that I was going to wire to the green wire on the ignition switch, and then from the switch to the No. 5 slot on the dash harness (No. 5 is currently empty, but will add contacts and wire). Does this sound correct to you?

P.S. How do you like my signature now?

[VetteVet]

Yes that is much better.
I figured you had a 67/72 but when you mentioned TBI and PCM it clouded the issue along with the SES light. I got the idea that you had a three hole dash from the part about the green wire to the key switch because with the seven hole there would be no green wire to the key switch cause you wouldn't have a temp light. The tan wire would still be there because the brake warning is in both clusters. When you said the 5 slot was empty, that was another clue that you had a seven hole since it is the wire for the temp light and the temp sender is moved to no.6.

The SES light should come on if you have the green wire on the switch and run it to the light anytime you go to the start position. The only concern I have is that once you wire the PCM wire to the key you might get a positive voltage backfeed into the PCM. Putting a small diode in the PCM wire would prevent that. There is probably a safeguard in the PCM for that possibility but unless you are sure of that it wouldn't hurt to be safe.

You'd have the same situation even if you just wired the PCM to slot 5, that's why I think the PCM may have this precaution.

Don't forget to post back when you get done so we know how it worked.
Happy Turkey day. VV

[coop34]

Got it all wired up. Thanks VetteVet! Now I just need to figure out how to change the temp light to say "Check Engine"