Lights dim when 2nd fan comes in

[Paul Glasson]

My cars light dim a fair bit when my cars second fan comes in. The fan obviously draws a fair amount of current and makes the car sound like a hovercraft, and certainly blows a lot of air. Is this normal?I can live with it as it does not affect me on highway driving as there is sufficient cooling for fan not to come in then. Just wondered if fan was drawing more than normal current?

[adrian jaye]

if its only started doing this I'd check the usual suspects, yours lights should not DIM so not in any order

1> battery, leads, grounds
2> engine ground cables
3> relevant fuses and relays
4> fuse board

and spray liberally with WD40

HTH

holla back if still no joy

Ade

[IceShark]

The fan might be drawing more than normal current when it kicks on but the real problem is probably your main wiring cables, especially grounds.

You have an '84 944 and I can guarantee if you have original cables the ground is crap. I just got done building and selling a new build of battery cables. The complete package is all sold out but I could sell you the upgraded main negative cables (in the later style rather than the crap style you have) and military/marine battery clamp for $49 USD and an additional supplemental ground from the front of the engine block to frame rail for $20. That will probably take care of the problem.

I just shipped the above over to the United Arab Emirates for around 30 bucks for under 1 week delivery. Shipping and packaging cost would probably be similar to Durban.

[Paul Glasson]

Well it looks like I must get under the car and have a look at the grounds. Have never had cause to do it up to now as this car has spent its whole life garaged when not in use so have never had a similar problem. Just have to search for grounds using Haynes and a search on this forum. If I need new cables I will contact you Ice Shark.
Battery was replaced about 1 year ago and alternator repaired so should not have problems with charging or battery capacity which could also cause this problem.Just another question. Do you silicone/grease coat the ground connections once cleaned and bolted back. Thanks guys.

[adrian jaye]

the engine ground , which there should only be one,
is at the back of the engine by the bulkhead accesisble from the top

and of course the battery ground

[IceShark]

adrain is right regarding the main grounds and you don't need to crawl under the car. But how exactly it is set up depends on the year of the car and if it is a left ot right hand drive since the RHD cars have the battery in the rear.

I think you probably have a RHD car as you are in South Africa, which I didn't consider first when I told you about my battery cables - they are for LHD cars.

This probably makes your grounds even worse, unfortunately. I've never seen a pre 85.5 LHD car in person but can guess how it is set up. You probably have a bare copper strap that runs from the battery to the sheet metal in the rear cubby hole and then another bare strap that goes from firewall to the bellhousing/engine block.

There are two problems that always come up: first is the terminals on the cables were just bare copper and mechanically crimped on, no solder or tinning applied. What happens is corrosion walks up the interface between the terminal and wire core resulting in resistance going through the roof. Second, there is something about these cars and the body. I believe it has to do with the galvanizing and the way the body was put together. The result is the body is not a very good electrical conductor after all these years.

One test you can do to see if this is a problem is take a pair of jumper cables, clamp one end of the two to a solid spot on the engine block and the other ends to the frame of the car. One good spot is the ground point on the forware frame rail under the headlight buckets (you will see several brown grounds bolted here). See if that makes a difference when your fans kick on. If it does you know exactly what the problem is.

It is probably impractical to run a new ground from the battery up to the engine block. I'd replace the ground cable from battery to sheet metal, firewall to engine block and then add a supplemental ground from the front of the motor to the forward frame rails.

That should be enough to take care of the grounding problems.

But if you have a RHD car you may also have a problem with your positives and need a supplemental cable. Since I have never seen your car I don't know how that wiring is set up, specifically how power flows from the alternator to the battery and off to the fuse/relay distribution. They have to be long cable runs which is not good for trying to transmit electrical current.

And yes, use silicone dielectric grease on the mating surfaces of the electrical terminals to prevent corrosion. Just a thin film applied with your finger is enough. Don't slop it on real thick as the excess will collect dirt and grime over time.