Doing "Surgery" on the Headlight Control Module

XJ-S
1

Being that I have two such modules and neither one works reliably (i.e. sometimes when I go to “dim” headlights the lights just go OUT instead :open_mouth: ) I’m going to experiment with one of the modules and see if I can get it working again. :thinking:

My understanding that what usually goes amiss with these modules is that one of the two mini relays inside the unit goes on the fritz. The other problem is usually a crack in the circuit board (solder).

I’m thinking that if I put the unit in my oven for about 20 minutes or so @ 200-225 degrees I can soften the black “goo” (RTV sealant?) in the unit (similar to the process used when r/ring the fog light lenses) and then be able to slide the circuit board out of the covering for inspection, and then repair whatever is wrong (either re-solder the broken/bad solder or spay/clean up the mini relays with electrical contact cleaner).

Does this sound like a sound approach? I am worried that the heat might damage something else with the unit, but the melting point of tin solder is closer to 400 degrees F. and I have a hunch the plastic cover won’t suffer any ill effects at the proposed temperature. The electronic components should also have no problem with the temp., I would think.

2

200° F/100°C is not that much but I doubt it will help.
Only way is to force it open or cut the seam with a Dremel of something…

3

RTV silicone is heat resistant up to 200 deg. C. It won’t melt even above 500.
Butyl rubber however - easily, 100 deg. C is enough - but yhat must be butyl rubber, not silicone. Check with tip of the flat screwdriver (press). If going sticky = butyl.

As mentioned by Aristo, Dremel and cutting disc if you are willing to do the post-mortem. It will be post-mortem unless you’re extremely lucky.

Why not trying dim/dip from Volvo instead?

4

There is a Volvo unit that is interchangeable with ours? :confused: First I’ve heard of that … If so, hopefully it’s less $$ than the Jag unit … The current ones for sale on Ebay by one of the usual suspects = $170.00 … :open_mouth:

5

You can use any dim/dip module really, may be quicker than carving in corpse. Apparently volvo has most compatible - old volvos 240, 740 etc…

6

Thanks, Banger. Will check some of them out on Ebay … :slightly_smiling_face: