Headlight pod retraction issues 1994 S4 in Australia

[Rob Hayden]

G'day from Australia readers,

I have a lovely S4 which I've owned for a few years now and slowly working through it's issues. Finally a fully operational fuel gauge last week and now moving on to the one serious bug in this car that appears at this stage to be beating me.

For about three years now my left headlight pod (passenger side) is always staying up. Doesn't matter if the headlights have been turned on at the switch, or if highway flash has been used. Old lefty just stays up.

Dead cold in the morning you may get one or two complete actions from it, but after that, she's done for the day and wont lay down to sleep.

So after reading post after post after post on the three main Lotus discussion forums, I decided to attack the problem with some gusto. Two days later, it's Rob 0 / Lotus 1!

First I checked the operation of the green relay for the pod delay. All contacts cleaned, sprayed electrical contact cleaner down into the relay mount block, and also gave the block pins a decent clean with small probes. Then I did some testing here relating to voltage on Pin's 6 and 4 when switch activated or de-activated and also checked a solid earth at pin 8. Following down the loom to the actual pod control module, I can see that I'm getting suitable 12v signals on the two wires from the relay that signal pods up and pods down to the control module.

So then I removed the control module and opened it up to check for the standard issue of scorched transistors. The internals of the unit look like brand new, with no evidence anywhere of water ingress or heat related damage.

Five wires going into the unit and four wires coming out, two to each pod lift motor. Of the five going in, two are fused power inputs. One quite heavy black earth, and two control wires for up and down signals from the timer relay. That part was pretty straightforward.

The pod control is an earth switching unit which is able to reverse polarity on the two motor wires depending on the up or down signal received from the timer relay. It also has sensitivity built in to ensure that when the motors start to draw amps from pushing against either the up stops or down stops, that it stops the negative feed instantly so the motors don't burn out.

I removed the four pins from the plug to be able to have a play with the four wires going to the two motors. First thing I did was swap wires 1 and 2 over to positions 4 and 3 and vice versa. By rights this should have flipped my problem from the left staying up, to the right staying up. But the S4 had other ideas. Even though the right motor was being controlled by the left feed and vice versa, the left pod stayed up and the right behaved perfectly. So that was quite strange to say the least.

So next step was to remove the left motor which when opened looked brand new with zero damage to the gears. Irrespective, they got cleaned and re-greased then put back together. Then the rod was removed and I can easily articulate the headlight pod by hand. There is no detritus laying in the bottom, the car is really clean and the headlight moves really freely.

If I apply an external battery supply directly to the left motor wires the unit operates perfectly, both up and down when you flip the feed wires around. There's no bouncing, just a lovely fluid and fast movement of the pod in both directions.

So just to see what happened, I went to a Lotus supplier locally to me and purchased a new set of transistors and heat sinks for the controller board and fitted them in. Put it all back together and it made no difference. Lefty still stays up.

Then to really confuse matters, I flipped wires 3 and 4 from the controller to the left motor. Then operated both highway flash and headlights on/off. Sure enough one went up as the other went down as expected, but good old Lefty behaved perfectly in both up and down movements, although out of sync with the right side.

At the hair pulling stage now. Nothing is really making any sense. Signals appear to be coming from the timer relay just fine. Signals are also going to the lift motors and there is no binding of the motor or the left light. With wires reversed, it works perfectly. Put the wires back to stock and up she goes and thats where she stays.

Looking through the forums there isn't too much info on these pod control modules. There's workarounds for the timer relay but nothing to defeat a control box if one is failing apart from trying to track down a Fiero one form 30 years ago but that's not going to happen in Australia anytime soon.

Can anybody help, point me in the direction of some data or thread that I may have missed before I go completely spare?

Pic below of my old girl for your enjoyment.
 

 

[fjmuurling]

Try some new wires from the podmotor to the pod module