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75 2.0 - just started driving it to work daily last few weeks, has been running perfect.

yesterday on the way home i got caught in a major downpour but other than a few drips at the window, stayed fairly dry - not a drop in the trunks, engine area dry as well,- but i did try to use the fresh air fan that other than the low speed does not seem to really work at all, even at low, its hard to get it to go, so

- the alternater red lite comes on, tach goes to zero, and volt meter is on not reading anything. - checked all connections to the coil etc , fine, and no fuses popped.
- this is the weird thing, when i slid the fresh air fan controller over to off position the tach jumped back up-kind of, but not fully as i reved the motor it jumped up, but on idle dropped again, i didnt think they were supposed to be on the same circuit, but they must be. -lights all turn on fine, car runs idling fine, - so i dont think its the alternator or coil- has to be some kind of short at the fresh air fan?

anybody else ever have something like this before? one time i remember that fuse blowing, did not ever figure out why, but i just put the new fuse in and everyting went back to normal, but now that was like a year ago, and it leaves me wondering, did i turn that fan on at that time, blow the fuse? i really never use that fan since it doesnt really work anyway, but i was desparate for some air flow with it being 90 degrees, and raining.

i'm going to take a closer look at lunch time, hoping i can figure it out because i have to driving it tonight about 30 miles to a meeting then home 45. i dont want to be stranded on theside of the road somewhere with some wierd electrical issue.

i did check the tach lead on the coil and it seems to have a good connection, also i replaced the FI harness and the igition harness last year (Jeff Bowlsby) and all has been fine since, plus it is running. i would think that if the alternator was going out it probably would not be running, right?

IIRC, all those items share a common thread; relay board in the engine compartment. FYI, it will run w/o an alternator. Until the battery dies.

I replaced that board a few years ago, when i replaced the wiring harnesses, voltage regulator etc. I can place the voltage meter check to see if the alt. is working,charging. it may be that it is, but that the tach is shorted either under the dash or at the tach - but i will check the board connections too.

The tach goes thru the relay board harness' also, doesn't it?

Intermittent problems are hard to diagnose. My dad's '76 2.0 had a similar issue with the tach. It sounds funny, but the only thing we noticed is that the tach quits working when the sun is shining on top of the dash.

cm

O.k. so I went out to recheck fuses and throw a meter on the coil and battery-good solid 13.75v. So next was wires and fuses. The #4 fuse from the right had popped.
Now the thing is if I slide the fresh air fan lever over just past the point of low speed it will short that circuit and this itlst the culprit - the exact how and why alludes me

That is weird, mainly because the 4 th. fuse from the right is fuse #9, which had nothing to do with the fresh air fan. That would be fuse #8.
However, fuse #9 does cover the taillights. Ah ha, rain - taillights, some connection possible there. Leaking taillight cover?
Tom

- well its for sure on the #9 because i made it blow the fuse again by turning on the fan yesterday.
- check the lights, no leaks, i have new seal on that, no issue.

Possibly the fan was connected to the wrong fuse when the wiring harness was changed (?)
In the fan switch both +12V and ground are present so it would be possible to get the fuse blowing when fan speed 2 is on if the switch is not correctely connected.

/Lars

Lars,
thanks for the thoughts. when referring to the fans switch, do you mean the fan controls? if i take the cigarette tray out, i can see where 3 wires attach into the right side of the board. looks like they connect to tabs that become the contact plate that the contacts slide across to make contact and complete the circuit. is that where you are referring to?

Phil

Yes its the fan control switch I mean.

In the diagram linked below (for a 1974 model) you will find the switch E9 in the lower left corner and the fan below (V2) with its internal resistors etc just above.

It ought to be four wires to the switch: one earth (Brown) and three whiteish (one for each fan speed).
Also a red white (+12V) to the blue lamp (K8) and a short brown/white for earth to the lamp.

Try to see if all these are connected in your car as per the diagram.

Link to wiring diagram:
1974 wiring diagram


/Lars S

Picture of the switch (upside down I believe) , the brown earth wire can be seen at the top, the three whiteish wires going to the fan should be connected to the three spades at the upper left in the order white/blue - white/yellow - white from bottom and up.

The single spade to the right of these three is the lamp earth wire and should be connected to one pole of the lamp with a short brown/white wire.
The red/white wire should go directely to the other pole of lamp.

/Lars S

So i finally got the car back from the shop, so i tried to fiddle around a bit with this , but i didnt accomplish much!. But i was able to verify that all 3 white wires are attached with good connections. it also appears that the ground wires are attached properly as well..

- the fan will slowly come on if the contacts are set in the middle speed. but not a full speed, but i was just pushing around on stuff with a screw drive and the fan suddenly went into a much faster mode so i know there is a connection issue and we know the fan works. but it only ran that way for about 30 seconds. then slowed down again. I was able to cause this to happen randomly 3 times, not sure which connection is bad, i think i need to pull this thing out completely to inspect it better -
a
so how do you get this thing out of the dash? and where within the unit could it be shorting out?
Does anyone have a know clean working unit that i could buy or atleast borrow to test?

Thanks!

Phil

If you notice, center back there is a tang for 10mm stud or bolt i forget which, which has to come out/off then pull forward disconnect the control cables and wiring.
Its pretty simple device just sliding contacts that can & do corrode.

Once getting it out you will see the contact paths for the different fan speeds and most likely you can get it functional by cleaning and if neccesary carefully bending the pic up for better contact.

I suspect the red/white wire to be involved in the shorting - check all wires when the thing is out.

/Lars S

Thanks guys, i'm going to take a closer look tonight after work. You might be onto something with that 12v red/white wire, - the contacts dont look bad but i will clean them good first, - i can tell you that the light that shows the fan is on comes and goes, does not stay on sto that connection is bad for sure. ( the little light on the right side)

If the fresh air box drains are clogged water would have gotten into the fan/resistor area and shorted the resistor.
Or, the resistor could have just failed to a dead short. I have a blower that doesn't work on the middle setting, luckily it's not a dead short.

All speeds should be possible to engage but I think you can find a small spot on the control arm movement between every speed setting where the fan goes off on these type of controls...this is to prevent engageing two speeds at the same time...this is how mine seems to work...


/Lars S

My FA fan was blowing fuses, I removed the box and found the fan wheel was jammed by one of the balance tabs that fell off. Now it works fine on low and medium but hte high speed won't work unless I hold the control lever down.

Interesting the different issues with these fans. The fan works fine, was bench tested before installing. I replaced the original fan with this one a couple years ago because of this issue. So its not the fan, I messed with controls last night. Pulled controls out sanddd the contacts, checked ground connections. At this point I still think its the contacts/circuit in the controls. I want to source another set of fresh air controls to try.

That's true, but mines sitting on the floor where I was doing airflow testing for my ac kit <-- shameless plug
Blower resistors fail fairly often. I've done my share as a mechanic.

i may recheck that at some point but right now i want to test a different control unit because ive had 2 fan boxes installed and they both acted the same way - so my thought is to test a different controller/sliders one that tested fine in another vehicle-
btw- i want to be put on the list for that A/C box, i was reading your thread on that and it seems like it might be a bit of work but worth it for those of us in the south!
- there is another member that had put together a mount etc too i think and is using a newer a/c compressor that will draw much less drain on the motor- i just dont know about running the a/c lines etc. -
any way i digress--- i need to test a different controller --