Ignition relay keeps blowing
Ignition relay keeps blowing My ignition relay keeps blowing. Has anyone else had this problem? What is the best way to troubleshoot for this type of problem. I replaced it this morning got two starts out of it and it blew again.
Fuses blow. Relay do NOT. What did the relay do when it "blew"? How could you tell it "blew"? Do you understand how relays work and why they are used? There are 2 circuits in a relay: control and load. Which one "blew" and why? The control circuit is LOW current(or should be). The load circuit is high current. If you OVERLOAD the load circuit you can damage the contacts, but not usually after the second time applying a load unless the load is extremely high. The relay is rated for the job it does. Are you using the correct rated relay. Are you using a 10 amp relay in a 30 amp circuit? Is the load pulling more current than it should? Did you examine the relay contacts after it "blew" to see if they are pitted? You can jump out the relay load contacts using a jumper with some terminals on it and measure the current when the load is applied using a clamp on amprobe. See if the current draw matches the rating of your relay. Is the load pulling too much current? That's an overload and will damage the contacts. The contacts then cause high resistance and become a load themselves. The pitted contact will drop voltage and rob the load of some of the voltage it needs to do its' job.
It's definately the relay that is blowing and not the fuse the fuses are fine. I understand how a relay works, it acts as a switch when power is applied it closes or opens a current and allows power to continue on. I have the GM digital manuals now so I will just have to use that for a good diagnosis, thanks for the help though. And yes relays do go bad, maybe I just didn't use the right term when I said "Blew" maybe I should have said fried
OK, enough with the semantics. You haven't said which side of the relay "blew" or "fried". Is it the control or load side. Have you removed the relay from the socket and put a jumper in its' place and used a clamp on probe to measure the current being drawn? An ingnition is not a high current circuit like a motor circuit. It does have high voltage on the secondary side, but not high current which would kill a relay. Have you done voltage drops and continuity tests? You have to do some point to point troubleshooting to find this problem and you have to know what you're looking for when you check test points. If you don't know what voltage or current you should see you don't know if it is correct or not. You're just wasting time making tests at that point which lead no where unless you know what to look for. If you knew what to look for you probably wouldn't be asking this question.
Last edited by eallanboggs; Sep 30, 2009 at 08:26 AM.
Thanks for your agreement that really help the situation!
ellanboggs, I wasn't trying to be a smart ***, and I completely understand what you are saying and that was why I said that I have the GM manuals so I can correctly troubleshoot the problem with knowing what the volts and resistance is supposed to be for the particular circuit. I was just asking the question for a quick fix if someone else had a similar problem but I guess no one else has. When I get it figured out I will let you know what the problem was. Thanks ellanboggs!
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How about some general rules about electrical components in cars/trucks?
Relays are highly reliable(not just in cars, but other places too). That's not to say they don't fail, but if they do it's probably because a under rated realy was used.
Ignition circuits are low current compared to motor circuits. Motor circuits use relays for this reason. I guess you could overdesign a vehicle and put a relay it it for everysingle function, but what would the point in that be.
Relays don't fry or blow(usually) unless something has been wired wrong or there is a wiring problem(short to ground or power) or the wrong relay has been used. Short to power usually means a fuse blows(not a relay) and short to ground usually means something won't work as expected. Don't forget in these days of PCM and ECM the driver circuit can supply EITHER power or ground unlike in the old school days when ground was already there and you were looking for 12Vdc.
You still haven't said if it is the control or load circuit that is at fault. Do you know which one it is? I'd unplug everything on the load side and see if the relay still dies. Actually, I wouldn't do it that way since that can get expensive. I would find the problem, fix it, plug in a new relay and drive away.
Relays are highly reliable(not just in cars, but other places too). That's not to say they don't fail, but if they do it's probably because a under rated realy was used.
Ignition circuits are low current compared to motor circuits. Motor circuits use relays for this reason. I guess you could overdesign a vehicle and put a relay it it for everysingle function, but what would the point in that be.
Relays don't fry or blow(usually) unless something has been wired wrong or there is a wiring problem(short to ground or power) or the wrong relay has been used. Short to power usually means a fuse blows(not a relay) and short to ground usually means something won't work as expected. Don't forget in these days of PCM and ECM the driver circuit can supply EITHER power or ground unlike in the old school days when ground was already there and you were looking for 12Vdc.
You still haven't said if it is the control or load circuit that is at fault. Do you know which one it is? I'd unplug everything on the load side and see if the relay still dies. Actually, I wouldn't do it that way since that can get expensive. I would find the problem, fix it, plug in a new relay and drive away.
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Verdad Gallardo agreed, its something in the wiring I just have not found it yet and I believe it is the control side but not sure. That is what is throwing me off is the fact that none of the fuses are bad it is just overheating the relay and burning them out so its definately something in my wireing. Gotta love gremlins
This is not that complicated. It's either the control circuit or the load side. Let's scrap the relay for now. Throw it in the garbage can. Make a jumper that you can plug into the relay socket(LOAD side). You'll need two terminal and a section of wire long enough to wrap a clamp on amp probe around. Plug in your jumper. Do the device(Ign circuit) work. Move on to control side. When the enable signal(12Vdc) should be present at relay control circuit socket terminal measure it with your DVOM to make sure the correct voltage is present. Did you open up the failed relays for inspection? I sure would have. I'd want to know what was going on after the first failure not after 2 or 3. Does the relay coil chatter, hum or buzz? Is the enable signal(be it power or ground) stable or is it intermitten? This ain't rocket science.
Pull the cover off the relay and take a few pictures of the insides. Does it fail only as you start or while you are driving? that relay powers ALOT of things.
Last edited by 99RTA; Sep 30, 2009 at 04:24 PM.
Well it fails after I drive for a little while.
I went through all of GM's trouble shooting for the ignition relay. With a jumper wire all the mini fuses for INJ-1 INJ-2 ENG CNTRL AC and one other all get power. The ground side is good, The power lead side is good and the load side of the circuit is good as far as GM's manuals are concerned. I am at a loss. Maybe I just got a bad relay and I opened it and saw nothing wrong with it besides the smell of burnt electronics like when you fry an amp
I went through all of GM's trouble shooting for the ignition relay. With a jumper wire all the mini fuses for INJ-1 INJ-2 ENG CNTRL AC and one other all get power. The ground side is good, The power lead side is good and the load side of the circuit is good as far as GM's manuals are concerned. I am at a loss. Maybe I just got a bad relay and I opened it and saw nothing wrong with it besides the smell of burnt electronics like when you fry an amp
