1990 Chevy Suburban A/C relay only works when I tap it

Tiny
PUSHINGVWS
  • MEMBER
  • 1990 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Hi,

I am having trouble with my a/c fan coming on. If I switch it on in the cabin, then tap the a/c relay under the hood with a screwdriver it turns on. I tried 3 different relays, all with the same result. Any ideas?

Thanks,

Nick Fox


http://www.2carpros.com/forum/automotive_pictures/375939_relay_1.jpg

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Monday, June 29th, 2009 AT 11:28 PM

12 Replies

Tiny
BUDDYCRAIGG
  • EXPERT
Are you trying NEW relays?
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Monday, June 29th, 2009 AT 11:42 PM
Tiny
PUSHINGVWS
  • MEMBER
Yes bought two seperate new ones. All 3 do it.
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Monday, June 29th, 2009 AT 11:51 PM
Tiny
BUDDYCRAIGG
  • EXPERT
Ok.

Then if a relay doesn't "snap" shut hard enough to close the contacts, then it has to be a weak signal driving the magnetic coil.

Either a weak power supply, or a bad ground.
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Monday, June 29th, 2009 AT 11:54 PM
Tiny
PUSHINGVWS
  • MEMBER
Does that relay have a ground wire or are you talking about the fan motor being grounded.
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Tuesday, June 30th, 2009 AT 12:20 PM
Tiny
BUDDYCRAIGG
  • EXPERT
I'm talking about the relay.

I have a question. What does the terminals look like in the socket?
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Tuesday, June 30th, 2009 AT 12:55 PM
Tiny
PUSHINGVWS
  • MEMBER
They are spade terminals 6 of them
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Tuesday, June 30th, 2009 AT 3:53 PM
Tiny
BUDDYCRAIGG
  • EXPERT
No, I meant the condition of them.
Do they look discolored, is the plastic around them melted.

Sorry for the confusion.
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Tuesday, June 30th, 2009 AT 4:00 PM
Tiny
PUSHINGVWS
  • MEMBER
It looked a little nasty, so I took apart the male part of the socket and pulled out the individual wires, the red power wire looks like it may have shorted out at some point because it has burn marks on it and the plastic. Even so, it's still in pretty good shape and has a good connection to the relay. I just now finished up re grounding it hoping that was the cause. I even ran a wire from the original ground location to a better location on the chassis. I guess my next step is to look at that red wire. The volt meter says 13 volts though, yet it still only clicks on with a tap of the screw driver.

Thanks for your help, it's been very informative.
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Tuesday, June 30th, 2009 AT 8:19 PM
Tiny
PUSHINGVWS
  • MEMBER
Could it be the switch inside the vehicle? I turned the truck on, tapped the relay to get it started, then moved the switch from high, to the next one down and it worked, then moved it back to high and it worked, then moved it all the way to the lowest setting, and it wouldn't come back on
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Tuesday, June 30th, 2009 AT 8:26 PM
Tiny
BUDDYCRAIGG
  • EXPERT
I need to take a step back for a moment.

In your first post you said

Are we talking about a fan that cools the AC condenser, or are we talking about the blower motor that makes the air come out of the dash vents?
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Tuesday, June 30th, 2009 AT 10:50 PM
Tiny
PUSHINGVWS
  • MEMBER
Blower motor, sorry for the technical mis understanding. I fixed the issue. It was the control switch inside the dash.

I have to say I know a lot more about how my a/c works now.

Thanks,

Nick
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Wednesday, July 1st, 2009 AT 1:41 PM
Tiny
BUDDYCRAIGG
  • EXPERT
Glad it's fixed.

Even though I thought we were talking about a different circuit until you said how many wires were going to the relay, I hope something I may have said lead you in the right direction.
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Wednesday, July 1st, 2009 AT 3:38 PM

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