Kinda Silly Electrical Question

[Don L.]

From an electrical novice, is it possible to have a weak relay, meaning that the power goes through it, but too weak to fully power the object its set to power? Example: can a horn relay be opening/closing, but not well enough to get a strong signal to the horn? I know that if the ground is poor, the horn might not blow, but I'm not sure if the power going through the relay could be hampered by age, conditon, etc. Thanks guys.

[Joel T.]

Re: Kinda Silly Electrical Question

Don;

In general, the relay operation is binary... meaning it either engages and the horn blows or it does not... You might get some sort of horn pulsation if the relay coil is weak, the voltage is low or you have a poor ground.

It is possible that the relay coil works but the contacts are pitted/burnt to the point where current will not flow to the horns.

Get your voltmeter out and check relay output voltage when the horn button is pushed..

Hope this is of some help....

Joel

[Tom L.]

Re: Kinda Silly Electrical Question

The only "silly" question is the one not asked. Joel is correct, I had the same problem with my power window relay. It's switch operated properly and put the windows up for judging and when it was time to leave they wouldn't go down. 35 miles, 90 degrees and no air. A miserable ride home.

The scenario Joel described was exactly what happened to my relay, 8.5 volts on the load (output) side of the relay. Good Luck!

[Don L.]

Re: Kinda Silly Electrical Question

Thanks guys. My situation is that the alarm horn will not blow, but mearly "clicks" when called for by any of the switches. I replaced the horn with another correct horn and got the same result. I installed an aftermarket horn from the local parts store and voila! Cheap horn blows perfectly, correct horn(s) only click(s). Wanna get it right but running out of ideas.

Based on your feedback, I may have a situation where the relay is functioning but weak. Strong enough for the aftermarket unit, but not enough for the correct unit. Think?

[Kenny C.]

Re: Kinda Silly Electrical Question

When checking for proper voltage be sure to have a load attached (the horn must be connected). It is possible that if the contact points are corroded or pitted that with no load you can see a full 12 volts on closing but the connection be so poor that they break down under load and not be capable of carrying the load of the horn or window motor or whatever. Basically you must test under the same conditions that the relay would see during typical operation.

[William C.]

Re: Kinda Silly Electrical Question

The alarm horn is a long way from the relay, and depends on the frame for a ground. If the alarm horn works when activated outside of the car, I'd start by checking the voltage across the relay contacts for excess drop (bad points in the relay) and if that is ok, begin with the ground to the frame and clean/check every connection between the horn and the relay. That should solve the problem.

[Don L.]

Re: Kinda Silly Electrical Question

WOW! I'm so glad I posted what I thought was a silly question.

Bill, the correct horn does sound when powered directly - outside of the car. The car is a "body-off" restoration, so the frame is clean. I've tried my best to make sure I have a solid ground. I opened the relay and cleaned the points too. I have not checked the output with a voltage meter, but can and will (with a load on it - thanks Kenny) and see what I get.

I'm trying to understand what is needed for my upcoming Carlisle hunt.

[Terry M.]

Re: Kinda Silly Electrical Question

WOW! I'm so glad I posted what I thought was a silly question.

Bill, the correct horn does sound when powered directly - outside of the car. The car is a "body-off" restoration, so the frame is clean. I've tried my best to make sure I have a solid ground. I opened the relay and cleaned the points too. I have not checked the output with a voltage meter, but can and will (with a load on it - thanks Kenny) and see what I get.

I'm trying to understand what is needed for my upcoming Carlisle hunt.

Be sure you have not coated the frame so well that the paint/coating acts as an insulator from ground. The ground connection needs a good solid connection to carry the amps of the horn. You might be surprised how many amps it takes to make noise from our old-school horns. Modern horns (especially aftermarket units from your FLAPS) are electronic and take far less amps than the electro-mechanical horns that are OEM in our Corvettes.

[Don L.]

Re: Kinda Silly Electrical Question

Be sure you have not coated the frame so well that the paint/coating acts as an insulator from ground. The ground connection needs a good solid connection to carry the amps of the horn. You might be surprised how many amps it takes to make noise from our old-school horns. Modern horns (especially aftermarket units from your FLAPS) are electronic and take far less amps than the electro-mechanical horns that are OEM in our Corvettes.

Thanks Terry. So far, I've cleaned the ring terminal for the ground wire and cleaned (sanded) the frame where the ring terminal attatches. I've also cleaned the male and female terminals on the relay and harness connection.

Is there someplace else that should be addressed?

Hmmm. Maybe the connection between the wire and the ring terminal is corroded/bad. Hadn't thought of that before now...

[Kenneth T.]

Re: Kinda Silly Electrical Question

Isn't there also a flasher involved

[Terry M.]

Re: Kinda Silly Electrical Question

Thanks Terry. So far, I've cleaned the ring terminal for the ground wire and cleaned (sanded) the frame where the ring terminal attatches. I've also cleaned the male and female terminals on the relay and harness connection.

[color=green] this is good, and what I had in mind.[color=/green]

Is there someplace else that should be addressed?

Hmmm. [color=green]Maybe the connection between the wire and the ring terminal is corroded/bad. Hadn't thought of that before now...[color=/green]

The wire can corrode under the insulation, and this can be hard to detect and harder to correct. The wire can also break under the insulation and this can be harder to detect. A likely suspect for this kind of issue is where the wire passes through the bulkhead. The best method of detecting these kinds of issues is to measure voltage drop on the span of wire while the wire is under load.

A voltmeter connected to each end of the wire while trying to blow the horn will show the voltage drop on the wire. It should show zero volts when the horn is silent and less than a volt when the horn is blowing. A digital voltmeter works best for this task, but if one is checking the alarm horn (which has a pulsing signal) it might be easier to jumper the contacts on the turn signal can so the horn doesn't pulse.

[Don L.]

Re: Kinda Silly Electrical Question

The wire can corrode under the insulation, and this can be hard to detect and harder to correct. The wire can also break under the insulation and this can be harder to detect. A likely suspect for this kind of issue is where the wire passes through the bulkhead. The best method of detecting these kinds of issues is to measure voltage drop on the span of wire while the wire is under load.

A voltmeter connected to each end of the wire while trying to blow the horn will show the voltage drop on the wire. It should show zero volts when the horn is silent and less than a volt when the horn is blowing. A digital voltmeter works best for this task, but if one is checking the alarm horn (which has a pulsing signal) it might be easier to jumper the contacts on the turn signal can so the horn doesn't pulse.

I understand and will do it just as you explain. Thanks much.

Keneth, there is indeed a flasher involved. It's right next to the relay, under the storage tray. I swapped it out with an aftermarket unit to test it, but no-go - still no luck.

I believe the original/correct horn is somewhat fragile, in that it heats to activate and therefore, has a limited life where this is concerned, so I was thinking I'd use the cheapy horn for the load when testing, unless this team thinks I should use the correct horn. Yes/ No?

[Terry M.]

Re: Kinda Silly Electrical Question

I believe the original/correct horn is somewhat fragile, in that it heats to activate and therefore, has a limited life where this is concerned, so I was thinking I'd use the cheapy horn for the load when testing, unless this team thinks I should use the correct horn. Yes/ No?

In the OEM horn there is a set of contacts, and those can function poorly. The only way to them is to take the horn apart. On the other hand, one would expect those contacts to show poor function when bench testing the horn. Don't ignore the connector that brings power to the horn.

[Les G.]

Re: Kinda Silly Electrical Question

You have to be careful in cleaning the contacts on the horn relay. Check if they are pitted or burnt before cleaning. When you clean use a very fine sandpaper or a contact file if using sandpaper fold it in half place it between the points and close the contacts gently move the sandpaper back and forth. Does your key alarm work? If it does that says the coil in the horn relay is good. That coil makes the buzzing sound for the key. I have extra horn relays both original and Delco replacements that are not good for judging. It all depends on the year.

[William C.]

Re: Kinda Silly Electrical Question

The horn may indeed be an issue, as the bench test will usually be performed at a higher voltage than the horn will see in the car due to voltage losses in the wiring to get to the rear location of the horn, as well as the connections to get to it. If you have access to a variable voltage power supply I'd test it at lower voltages and see how much voltage tolerance it really has.