Removing and testing a relay
#1
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Simple question this time. ![Smile](https://www.gmforum.com/gm/images/smilies/icon_smile.gif)
In response to Danthurs' excellent write-up on how to change a blower motor, he recommends checking the maxifuse and relay first. The former was not an issue, but for the life of me, I can't figure out how to remove a relay, much less test one.
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In response to Danthurs' excellent write-up on how to change a blower motor, he recommends checking the maxifuse and relay first. The former was not an issue, but for the life of me, I can't figure out how to remove a relay, much less test one.
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Here'* how to test. https://www.gmforum.com/t279561/
Getting them out is a bit of a pain. You need to pull it out. The relay is inside a box that slides on a rail on the bottom of that box.
Getting them out is a bit of a pain. You need to pull it out. The relay is inside a box that slides on a rail on the bottom of that box.
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Thanks, Dan; I must have missed that.
Last edited by SignOfZeta; 11-09-2009 at 12:31 AM. Reason: Got bored. Tested anyway.
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Duplicate post; keep reading.
Last edited by SignOfZeta; 11-09-2009 at 12:30 AM. Reason: Posted twice. My bad.
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I tested the relay for the blower motor (the one you're holding in the writeup). This one, unlike in the aforementioned relay test write-up, is a four-pin relay that is normally open. It'* also in a little plastic case to make installation easy, deinstallation tricky (there'* a tab on the top), and testing a bit of a pain, unless you have four hands. (I do not.)
Attachment 1616
First, if you peer inside, there are numbers next to the pins. Now take a look at the schematic on the top of the relay. It will look like the one in Danthurs' writeup, but different. You can see the control circuit on pins 85 and 86, diodeless, and the current flows through pins 30 and 87:
Attachment 1615
Guess I'm replacing the blower motor. I know I'm not going another New England winter without a defroster. Scraping ice off of the inside of my windshield is not how I'd like to spend the next four months.
Attachment 1616
First, if you peer inside, there are numbers next to the pins. Now take a look at the schematic on the top of the relay. It will look like the one in Danthurs' writeup, but different. You can see the control circuit on pins 85 and 86, diodeless, and the current flows through pins 30 and 87:
Attachment 1615
- Set your voltmeter to 200Ω, and touch pins 30 and 87. This relay should show infinity, as it is open when the control circuit is low.
- Take a fresh 9V battery, and wire it up to pins 85 and 86. (As it'* diodeless, you can hook it up in either direction. I did, just to make sure.) You should hear a click. Now, if pins 30 and 87 read close to 0Ω, your relay is good. Put it back in the car.
Guess I'm replacing the blower motor. I know I'm not going another New England winter without a defroster. Scraping ice off of the inside of my windshield is not how I'd like to spend the next four months.
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Colin... that diagnosis sounds familiar.
When we tested your blower motor connector and saw 12V+ on all blower speeds, that was essentially the same test. The only one we didn't do was check for the correct amperage at the connector.
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I've found that can be a misleading test in some cases. If you use say a battery charger, you can end up putting more amps to it and getting the motor to work. Yet in the car it fails to work.
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