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?
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.
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!
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…
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.
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…
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…
@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…
