Blower Motor Relays and Dash Switch

Hi Everyone,

I replaced both my blower fan relays today on my 72 S1 XJ6. Mostly successful.
Before I had no fans, now I have the following…

When I turn on the A/C, both fans come on low (dash switch off) All good. With the A/C off, when I turn the dash switch to low, I have no fans (no good). When I turn the switch to high, both fans come on high (all good). Then when I turn the switch back to low, the fans stay on high. Switching to off, both fans go off.

I’m thinking the dash switch is bad? Thoughts.

Second question…how do you get the dash switch out for replacement?

Thanks!
Jeff H.

Hi Jeff,

It sounds more like that the relays get somewhat confused, maybe re-check your connections?

You just can pry the switch out, but safer to dismantle the panel and push them from behind.

There are no relay indicated on the S1 fans diagrams, Jeff. Do you have aftermarket AC fitted?

Frank
xj6 85 Sov Europe

Hi Frank,

As far as I know the A/C is factory. Attached is the schematics I have for my S1
Interestingly I don’t have two G/Y wires at W1, so the two wires must meet inside the wire loom somewhere.

Jeff H

Hi Aristides,

I have rechecked, nothing looks out of place. If the new switch I’m expecting to arrive in a day or two doesn’t fix it, then more trouble shooting is in the works. Arrgg. Thanks for the tip on pushing the switch out from the back!

Jeff H.

Test the relays on the bench to be sure they work as they should.

Was indeed for late S1s, Jeff - but the AC specifics are not included in my wiring diagrams.
Fans must run with AC ‘on’, for system protection - ‘good’, as you say. As shown; fan speeds are operated by two discreet switches - the white/yellow goes through a resistor, and the green/slate bypasses it for ‘high’ speed. So for ‘low’ speed, the ‘high’ switch must be turned ‘off’, of course.

Which switch is eventually at fault is sort of guesswork, but there are no relays involved…

Frank
xj6 85 Sov Europe (UK/NZ)

Hi Frank,

There is only one dash fan switch. The low speed leg goes to the relay on the left which is shared with the A/C thermo switch. The high speed leg goes through the relay on the right.

Both relays are working correctly.

I have yet to test the low speed wire from the dash switch to the relay to make sure there is no break somewhere.

I’m still waiting on my new switch. I hope the USPS hasn’t lost it.

Jeff H

The high speed relay may hang occationally, Jeff maintaining ‘high’ speed regardless of switch selection…?

However, since the ‘low’ speed, (relay), activates with AC ‘on’, but not with fan ‘low’ - the fan switch is indeed suspect. You can of course check by swapping over the green/yellow and green/slate wires - to see if the fault moves. And of course verify the verifying light/green is connected to the correct terminal…:slight_smile:

But there should be two wires connected to the ‘low’ relay; one from AC and one from fan switch - are there? And if there is power on green/yellow with switch in ‘low’ to back up a continuity check. Continuity test on a specific wire requires the wire to be disconnected at one end…

That the ‘high’ relay stays ‘on’ in ‘low’ implies a stuck relay - or a relay still powered.

You may have two faults - and even with a simple fault; with several components involved it’s a lot of variants involved.

I trust the symptoms are the same every time you try - an intermittent fault complicates matters no end…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

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@jahmiata any luck with the new switch? Also have a '72 XJ6 with factory AC and just went through the blower motor circuit. The prior owner had blown the resistor so the low speed circuit was left open.

When testing a few heat-resistant upgraded resistors in the 2-4ohm range, I realized these Smiths motors have a really significant inrush/stall current. If the switch didn’t solve the issue, I’d be curious if the resistor is at fault. You mentioned the low fan stays on when switching from high back to low, so you could be bypassing the inrush phase by first getting the motors spinning in the resistor-less high circuit.

Also, if you get a chance, what resistance reading do you get from the OEM resistor?

The original resistors were 1,3 (low speed) and 0,75 ohms (medium speed), Harry - and, given the relative high start-up current, somewhere around 20W (at a guess). High speed, directly to motors - from that relay rated at 21A…

You can of course vary speed at will by using different resistances…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

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Did you manage to get the issue fixed? I have a 73 series 1 and I’m having the same problem that the high-speed blower has stopped working. The low speed works fine for the AC and when I push to the high-speed, the whole system shuts off

I assume only the fans stop, Minder…?

Do you have a three or two-speed set-up? Resistors are used to slow fans, the high speed have no resistor - so it is either the high speed switch or the relay failing. Locate relays and check (likely) black/white for power from switch - and green/slate to discriminate…

Frank
xj6 85 Sov Europe (UK/NZ)

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Thanks Frank.
Yes. Just the High speed fan stopped.
2 speed setup.
Is the relay by the driver side knee pad?
I’ll check the switch

On S2 and 3 the relays are indeed behind the ‘left’ side consol cover, Minder. Both had 3, later 4 relays (and fan speeds) in a single unit.

Don’t really know on earlier models without or without AC - but with only two speeds they likely omitted the relay. connecting the switch through a green/slate wire and a resistor to motors. And a green/yellow without resistor for high speed - but a thermal fuse is also involved there …somewhere…

Likely the switch itself faulty?

Frank
xj6 85 Sov Europe (UK/NZ)

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appreciate it. I’ll get it booked in with my mechanic.

Hi All

Sorry to no post a follow-up…no the new dash switch did not fix the issue. Same results as before. I just haven’t had the time to continue testing.

According to my schematics the low speed from the dash switch and the air condition dash switch run through the same relay. Since the fans come on low when the A/C is turned on I know the relay is good. My last avenue of hope so to speak is the wire running from the low speed side of the dash switch and that relay. Hope to test soon. I’ll let you know.

Jeff H.

The ‘low’ speed is automatically switched ‘on’ with the AC - the AC should not run without fans running.

The ‘relay’ is stated as a thermal breaker switch (? - diagram a bit bewildering) - an add-on with the AC. The ‘high/low’ switch is independently fed by light green wire; is it power on that wire?

Frank
xj6 85 Sov Europe (UK/NZ)