A coworker has an 84. The other day he shut it off and the fan for the AC and Heat kept running. He's determined it's one of the two blower relays. Problem is, he can't find the relay physical locations.

Any help would be appreciated.

I think they are behind the DIC... but I would check the big resister thingy on the air box under the hood.

When the fan stays on that is a prime cause.

I just double checked the 1984 service manual, and yes, that is their suggestion. If it runs only in high, then that's the place to look.

The relay is under the fan, on the airbox, under the hood.

Thanks Andy.
We are talking the fan for the cabin air, not the radiator fan, correct? If anyone has pictures, it would help.

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I know of only one Blower Relay on the '84. It's labeled A/C High Speed Blower Relay in this drawing and is located under the Blower Motor:

If stuck closed, it will cause the Blower to run at all times.

when I reviewed the 84 manual, it was clear that if the resistor failed, the fan will run.

Check both, but I would bet the resistor is toast. They don't last forever!

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Not so clear to me.

The Relay has two states, energized and de-energized.

In the de-energized state, the current flows through the resistor pack. Based on the Blower Switch position, the current goes through one, two or all three resistors, through the NC contacts of the Relay and on to the Blower Motor. This current is only there when the A/C is not in the OFF position and only with the ignition in RUN. So if a resistor were to open you'd lose that speed. If all the resistors opened, you'd lose all speeds except HI. If all the resistors shorted, you'd get HI speed from the Blower in all speed positions, but only with Ignition in RUN and the A/C set to anything but OFF. The Blower won't run at all times (Ignition or A/C OFF) with a Resistor Pack fault.

In the energized state, the Blower gets current directly from the Battery through a Fusible Link. The Relay is energized by current through the A/C switch and the Blower Switch. Again current is only there when the Ignition is in RUN and the A/C is in an other than OFF mode. But if the Relay were to have its NO contacts stick closed, current would flow from the Battery through the fusible link, through the Relay's stuck closed NO contacts and on to the Blower Motor at all times. You'd have to disconnect something (Battery or Relay) to get it to stop.

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Sure check both, but with no moving parts the Resistor Pack doesn't fail anywhere near as often as the Relay and when it does, it almost always results in lost non-HI speeds. I'd be very surprised if the Resistor Pack or any resistor within the pack is bad, given the original problem. Now once the Relay is replaced and the Blower Motor is not running at high speed all the time, he may find that one or more low speeds are not working. Then the Resistor Pack needs looking at.

Here's the schematic from the '84 manual:

Just as a follow up. He found and changed the relay under the blower itself. It's fixed.

Thanks!

sweet. Keep an eye on that resistor, tho... it's prone to age failure.

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He did that first. I think he's all set.

cool.

the resistor will last a LONG TIME. mostly because it is climate controlled inside the airbox... but it isn't a perminent thing.

They do last a long time depending on where you live. I bought the car from a guy who lived at the beach. The resistors were toast after only 8 years from the salt air. However, the last one has lasted me 16 years now. Since I'm about due I bought a spare while they are still under $15.
I learned my lesson the hard way when my interior timer failed ...all the NOS are gone and its only being reproduced at the exorbitant price of $120!