Brake warning light help.

[derotoreut]

I am trying to figure out why my brake warning light won't work. I understand it should come on when the truck is in the "On" or "Start" position, and go off when running (as long as there are no leaks or differential pressure in the system). When I turn the key it won't come on at all.

I have a new Painless wiring harness installed. I tested the warning light by putting a 12V power source to the wire at the proportioning (combination) valve and it does light up on the dash.

Sounds like the problem might be the switch at the prop valve. Does this sound right or should I be looking at something else?

[VetteVet]

You are a lucky guy because the wire on the prop valve is a ground wire and the light comes on when this wire grounds due to low brake fluid or pedal pressure letting the prop switch complete to ground. You can test the light by grounding this wire and turning the key on.

Normally the light will light up when the key is turned to the start position and go off when released unless the wire to the prop valve is grounded. There should be a ground wire going to the key switch for this purpose. I think the temperature light works the same way. Check and see if you have a black wire going to the key switch. If not then the key switch may ground internally for those two wires. They are light brown (brake ) and dark green (temp).

[derotoreut]

Too funny. OK I grounded the brake warning light and it does come on when the key is in the "On" position. Right now I can't test it in the "Start" position because I'm in the middle of a carb overhaul. When hooked up to the prop valve switch, the warning light does NOT come on in the "On" position. Are the Temp & Brake lights supposed to come on in only the "Start" position, or in the "On" and "Start" positions, and then go off when running?

I checked for a black (ground) wire at the ignition switch. I do not have one. The GM type ignition switch connection was prewired by Painless. This all started as a result of replacing my harness with the Painless harness. I am not able to get the Temp light or Brake light working. With this kit there is a Temp Gauge wire (Green #921). There is also a separate Temp light wire (Green #983). Both wires come out in the engine compartment. I tested the temp gauge by putting the Green #921 wire to ground and turning on the key. The needle pegged hot, which is what I would expect. I tested the temp light by putting the Green wire #983 to ground and turning key to "On". The light worked. I also tested the Brake light by putting the wire (Tan #975) to ground and turning the key to "On". This also worked.

I called Painless today to see how the two temp wires were supposed to be hooked up. They told me they are both intended to be connected to the temp sender. However when I connect them together and put them on the sender, the light does not come on in the "On" position. The same goes for the brake light; once connected to the prop valve switch it does not light in the "On" position (again unless they are supposed to only light during "Start", which I can't check right now). According to Painless they told me that their harness is not designed to go through the test light mode during cranking. The only way to make these lights work would be to connect them separately to a 12v source that only comes on during cranking, which would be starter solenoid wire (purple #919) at the ign switch. It seems that if I did this these lights would only serve a function of lighting during cranking and would not provide any protection indication as they were designed.

I'm confused on this because the Temp light wire (Green #983) and Brake light wire (Tan #975) go into the ignition switch as well as the instrument panel. Wouldn't you think if they went into the switch it would be to provide a momentary ground path for them to light during cranking? The other wire for the Temp Gauge (Green #921) does not go through the ign switch, but I would expect that it wouldn't; just like the stock wiring diagram shows.

I was thinking that maybe my prop valve was shot and not working, but that might not be the case if the Painless harness is not designed to test the lights during start up. What can I do to check this out? Any help is greatly appreciated.

[fixit-p]

The temp and Brake warning lights are only supposed to come on during cranking as a bulb check function (and of course during over heat and brake fault) the fact that painless does not incorporate a bulb check feature in their wiring IMO is crap and could possibly open them up to liability, because the only way you could possibly know that the bulb is burned out is with the bulb check feature and without it you could loose your brake system and never know because the bulb is burned out. The ignition switch would also have to support this function they are typically grounded through the housing. If you wanted to you could also install a relay to mimic this function with the following hook up.
#30 to ground
#85 to ground
#86 tap into purple wire from ignition switch at NSS
#87 to tan and green wires to cluster (brake and temp)
That will ground out the green and tan wires during cranking.

[Longhorn Man]

did you post and delete a similar question yesterday?
As mentioned, the lights are only tested in the crank or start position, not in the run position.
The reason you didn't mess anything up when you put power to that wire is becouse the positive wire turns to a ground when there is no power to it. So you powered the ground wire, and it grounded through the power wire. Funny how that works.
If you want to get this sorted out while the carb is off, disconnect the purple wire on the starter, or even unplug the neutral safety switch and turn the as much as you want (assuming mechanical fuel pump).
One other note, if you have a guage instermant panel (as opposed to a dummy ligh unit) then the temp light isn't supposed to come on at all... as wired by GM.

[VetteVet]

---

Originally Posted by derotoreut

Too funny. OK I grounded the brake warning light and it does come on when the key is in the "On" position. Right now I can't test it in the "Start" position because I'm in the middle of a carb overhaul. When hooked up to the prop valve switch, the warning light does NOT come on in the "On" position. Are the Temp & Brake lights supposed to come on in only the "Start" position, or in the "On" and "Start" positions, and then go off when running? Yes if you think about it if they came on in the run position they'd be on anytime the engine was running and we only want them on when there's a problem.

I checked for a black (ground) wire at the ignition switch. I do not have one. The key switch must be internally configured to ground these two wires when the start position is selected I mentioned that in the first post and Fixit-p also mentioned it in his post.



The GM type ignition switch connection was prewired by Painless. This all started as a result of replacing my harness with the Painless harness. I am not able to get the Temp light or Brake light working. With this kit there is a Temp Gauge wire (Green #921). There is also a separate Temp light wire (Green #983). Both wires come out in the engine compartment. I tested the temp gauge by putting the Green #921 wire to ground and turning on the key. The needle pegged hot, which is what I would expect. I tested the temp light by putting the Green wire #983 to ground and turning key to "On". The light worked. I also tested the Brake light by putting the wire (Tan #975) to ground and turning the key to "On". This also worked.

This is a test that simulates the sender going bad and is not the vehicle test, which grounds the wires internally when the key is set to start.

I called Painless today to see how the two temp wires were supposed to be hooked up. They told me they are both intended to be connected to the temp sender. However when I connect them together and put them on the sender, the light does not come on in the "On" position. Yes you removed the ground for the lights and unless the sender was bad, or a malfunction occurs in the sender to ground the wires, then the light will not come on until the key is selected to start.

The same goes for the brake light; once connected to the prop valve switch it does not light in the "On" position (again unless they are supposed to only light during "Start", which I can't check right now). It would be on all the time while you were running if that were the case.

According to Painless they told me that their harness is not designed to go through the test light mode during cranking. If the sender wires for the lights and were run to the ignition switch, and I think they are, and if the key switch was configured to ground internally as I believe it is, then it will test the lights automatically.

The only way to make these lights work would be to connect them separately to a 12v source that only comes on during cranking, (Not so, the lights are already connected to a separate 12 volt source in the dash circuit.) which would be starter solenoid wire (purple #919) at the ign switch.
It seems that if I did this these lights would only serve a function of lighting during cranking and would not provide any protection indication as they were designed. You are correct that's why you cannot wire them this way. When you get the harness all in, then you can test the lights easily by just leaving the shift lever in drive and turning the key to start. The lights should come on but the engine won't crank because the NSS is open. I'm thinking that Painless is FOS on the test not wired in, or else they misconstrued your question. I agree with Fixit on the liability issue , and like I said, if the key switch is correct the test will happen automatically. .

I'm confused on this because the Temp light wire (Green #983) and Brake light wire (Tan #975) go into the ignition switch as well as the instrument panel. Wouldn't you think if they went into the switch it would be to provide a momentary ground path for them to light during cranking? As I said above.

The other wire for the Temp Gauge (Green #921) does not go through the ign switch, but I would expect that it wouldn't; just like the stock wiring diagram shows. True

I was thinking that maybe my prop valve was shot and not working, but that might not be the case if the Painless harness is not designed to test the lights during start up.

If the painless harness routes the wires to the key switch and then to the instrument panel plug, When you turn the key to start the lights should come on. What can I do to check this out? Get a voltmeter and do a continuity check on the two wires from the prop valve and the temp light, to the key switch body, and turn the key to start and see if you get zero ohms.

Any help is greatly appreciated.

[derotoreut]

Thanks guys. All your responses are well taken and understood. I appreciate them all.

Longhorn Man: No I did not post and delete a similar question.

I was very surprised when the guy at Painless said their harness was not wired to test the lights. I will get my multimeter and check the resistance of the brake warning light wire to switch and temp light wire to switch with key in start position.

Thanks again, I will keep you posted on my progress.

[Longhorn Man]

i coulda sworn i had just answered the same Q. Oh well, just becouse I remember something doesn't make it true.

[derotoreut]

OK here's the latest on my brake light and temp light. I finished my carb overhaul this weekend and now able to start the truck. I found out that the brake warning light and temp light DO NOT come on when ignition is in Start position.

Both lights tested fine as mentioned before. I did not use my multimeter to check the resistance across each of these wires back to the ignition switch because I got everything done this weekend and was able to actually start the truck. I thought for sure these lights would come on when cranking. Maybe the guy at Painless is right, that this harness really is not wired that way.

Another thing I noticed was that with both the temp wires (gauge wire and light wire) connected to the sender, the temp light will come on as the truck warms up. I watched the temp light and it would slowly start to light up and would be dim. The more the truck warmed up, the brighter that light got until the temperature reached the normal operating temperature. Once warmed up the temp light is on full bright.

I know these lights work, but they just don't come on when cranking. Any more suggestions?

[VetteVet]

---

Originally Posted by derotoreut

OK here's the latest on my brake light and temp light. I finished my carb overhaul this weekend and now able to start the truck. I found out that the brake warning light and temp light DO NOT come on when ignition is in Start position. Do you have the ignition switch mounted so that it is grounded to the frame and back to the battery negative

Both lights tested fine as mentioned before. I did not use my multimeter to check the resistance across each of these wires back to the ignition switch because I got everything done this weekend and was able to actually start the truck. I thought for sure these lights would come on when cranking. Maybe the guy at Painless is right, that this harness really is not wired that way. You have got to check the continuity between the key switch body and the terminals where the brake light and the temp light connect to the key switch when the key is turned to start. Otherwise you won't know if the two lights are grounding. It wouldn't make any sense to run the wires to the key and then to the console if the key switch wasn't supposed to ground the wires. They would have run them directly to the console.

Another thing I noticed was that with both the temp wires (gauge wire and light wire) connected to the sender, the temp light will come on as the truck warms up. I watched the temp light and it would slowly start to light up and would be dim. The more the truck warmed up, the brighter that light got until the temperature reached the normal operating temperature. Once warmed up the temp light is on full bright. That is exactly how the sender would work. It is a variable resistance to ground. IOW as the engine warms up the resistance to ground to complete the circuit for the light or gauge, gets less and less and the light comes on dim and the needle on the gauge moves toward hot. Now here is the problem, you need a different sender for the gauge than you do for the light. The light sender has a lot more resistance than the gauge sender and won't let the light begin to come on until the engine temp gets up to the critical range and then full on at the overheat temperature. We're talking two different senders here. My question is just like Longhorn Man said " if you have a gauge dash why do you have a temp light?". You can have both but you have to have two senders and the pins in the console plug have to be rewired.

I know these lights work, but they just don't come on when cranking. Any more suggestions?

[derotoreut]

Still working on this problem with no luck yet. Thanks for all your help.

Do you have the ignition switch mounted so that it is grounded to the frame and back to the battery negative As I mentioned before the ignition switch was prewired by Painless and I just plugged it into my ignition switch. I did however install a new switch. Is there something I should do differently to ensure it is grounded to the frame and back to battery? If it helps I did install several ground straps throughout the truck. One from engine to frame; one from frame to inner passenger fender; one from frame to bed; one from cab to frame. The only one I haven't completed is engine to firewall.

You have got to check the continuity between the key switch body and the terminals where the brake light and the temp light connect to the key switch when the key is turned to start. Otherwise you won't know if the two lights are grounding. It wouldn't make any sense to run the wires to the key and then to the console if the key switch wasn't supposed to ground the wires. They would have run them directly to the console. Yes I will do this. I thought I did it today, but I didn't check it right. Sorry, I'm not really electrically savvy. I will try again tomorrow.

My question is just like Longhorn Man said " if you have a gauge dash why do you have a temp light?". You can have both but you have to have two senders and the pins in the console plug have to be rewired. I'm not sure! I attached pictures of my gauge panel with the brake light and temp light grounded so you could see it. I have the seven gauge panel. It also has brake light and temp light at the fuel gauge. I thought this was how this panel was configured. My pins in the console plug have both gauge and light going to it. Let me know.

[derotoreut]

Hey guys I'm still working on this light issue. I talked to someone different at Painless today and he said the opposite. He told me the key switch is wired to do a bulb check when in start position. This makes more sense because both the temp light and brake warning light wires go into the switch.

As VetteVet suggested, I did go back and check to see if there was a ground between the switch body and wire terminal on back of switch when cranking. It did not ground. Does this now sound like it would be the switch? You mentioned that the switch has to be internally configured to ground during cranking. By the way I replaced my old switch and key cylinder with a new switch. Is it possible that some are not configured to internally ground that way? BTW the switch is installed and mounted into the dash and not hanging, so it should be grounded.

Also please take a look at my previous thread where I included pictures. My 7-gauge panel has temp gauge, battery and oil (besides speedometer and fuel). It also has the temp light and brake warning light in with the fuel gauge. Isn't this the standard configuration for this style instrument panel?

[fixit-p]

Yes all switches are not created equal some do not ground when cranking. Below is a screen shot of the Cole Hersey ignition switch listings the far right column shows the functions for each position or the switch could be bad.

[derotoreut]

This may be my problem. I bought a reproduction switch and not an OEM. I probably should have spent a little more on the original replacement. I tried to look up the switches that you show but had no luck. Where do you suggest I get it from?

Also any comment on the instrument cluster? What is the standard configuration for a panel with gauges? I was being questioned why I would have a temp light if I had a temp gauge. I thought my instrument panel was typical, but maybe not!

[fixit-p]

Have you tried O'Reilly's http://www.oreillyauto.com/site/c/de...2018&ppt=C0039

If you have a gauge cluster the temp light while it is still there physically it is inoperable, you could use it but as mentioned you'll need to use a different sending unit to keep the two systems isolated from one another also the sending units are different for light and gauge. As mentioned the cluster plug is pinned differently for the 2 systems.

[derotoreut]

Originally Posted by fixit-p

Have you tried O'Reilly's http://www.oreillyauto.com/site/c/de...2018&ppt=C0039

I'll check it out thanks.

Originally Posted by fixit-p

If you have a gauge cluster the temp light while it is still there physically it is inoperable, you could use it but as mentioned you'll need to use a different sending unit to keep the two systems isolated from one another also the sending units are different for light and gauge. As mentioned the cluster plug is pinned differently for the 2 systems.

My real question is what is standard with a gauge panel? Does the 7-gauge panel normally have the temp light too? My pin connector is wired for temp gauge and temp light. It seems kind of crazy that they would put the temp light in a gauge panel if it was not to be operable. I understand the need to have a separate sending unit. Is this what was done when there was a temp gauge and temp light? I'm just trying to understand what a normal 7-gauge panel looks like as well as figure out what to do for my configuration. Thanks.

[fixit-p]

....

Originally Posted by derotoreut

I'll check it out thanks.



My real question is what is standard with a gauge panel? Does the 7-gauge panel normally have the temp light too?No light but some of the components are there. My pin connector is wired for temp gauge and temp light. It seems kind of crazy that they would put the temp light in a gauge panel if it was not to be operable.Not if you consider doing so cuts down on inventory, allot of manufactures make parts that can be used in various configurations I understand the need to have a separate sending unit. Is this what was done when there was a temp gauge and temp light? I'm just trying to understand what a normal 7-gauge panel looks like as well as figure out what to do for my configuration. A normal seven gauge panel has the circuit for the temp light on the printed circuit board, no light installed even though the lens is there and the wire is omitted from the cluster plug Thanks.

[Longhorn Man]

...

Originally Posted by Longhorn Man

...if you have a guage instermant panel (as opposed to a dummy light unit) then the temp light isn't supposed to come on at all... as wired by GM.

[derotoreut]

Holy Switch!!! What a lesson. You guys are right that all switches are not created equal. My problem has been solved and determined to be the aftermarket switch that I bought. Once I replaced this reproduction ignition switch with an original AC Delco switch, my problems were solved. My temp and brake warning lights now work when the switch is in the start position. Thanks for all your help and patience. You guys are awesome.