1991 VDP brake warning inverter relay

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Can anyone help with the location of the brake warning inverter relay location on a 1991 Vanden Plas? everything I have read does not check with the wiring from the combined pressure switch. also looking for a green relay on a red connector? have both knee bolster off and can not locate this relay? pin 2 from pressure switch has a BR wire, not BLG as shown in the electrical guide

Hi Krash, welcome to the forums, sorry but I am not aware of a ‘inverter relay’ on a ‘40? Would it go under another name?

Krash,

I don’t know which wiring diagram you are looking at, but the one for a '91 XJ40 in the JDHT CD-Rom JHM1130 which I am looking at shows that the wire from pin 2 of the 5-way Blue connector of the combined pressure switch connector is indeed 'BR".

As Robin says, I too do not recognise a “brake warning inverter relay” in that circuit. AFAIK, there are three relays there, the ABS ECU relay (blue base), the Main relay (white base) and the Pump relay (yellow base)
I don’t see any relay in that circuit with a red base.but there are relays with a red base in the Cigar lighter, the Heated rear window and the Headlight washer circuits. Any of those circuits concern you?

Bryan and robin thanks for the quick response. I have a combined pressure switch to replace the blue topped one. The logic from pin 1-2 is reversed from the blue top. Where by the brake warning inverter relay. I think I’m getting the xj6 and the xj40 confused. My vin # SAJKT1744MC646521. Again any and all help would be appreciated. Where can I get the manuals you mentioned previously. Thanks again!! You are the best !!!:grin:

That noin-NA VIN is for a late 91 XJ40 VDP 4.0 litre, 4 door with auto tranny and driver-side airbag.

The ‘manual’ to which I referred , JHM1130, is in CD-Rom format and I can only suggest you do a search on E-Bay etc to see if you can find one for sale since JDHT no longer supply them.

I still have no idea what you mean by “brake warning inverter relay”. Where did you pick up that description?

My wife’s 1990 XJ-S developed a bad ABS accumulator and pressure switch. I replaced them with GM parts and have a recommendation for the re-wiring to accommodate the different GM switch logic. “Make a 2 or 3 inch wire link with a 1/4 inch spade connector at each end. Pull the ‘‘Brake Warning Inverter Relay’’ out and set it in the spares box. In our US Spec car the relay was green in a red socket behind the driver’s side knee bolster. Stick the wires from your wire link in pins 85 and 30 of the relay socket. The relay was there to invert the signal from the Jag switch which is inverted from the GM version. Doing away with the relay brings you back to function and generates a spare part. Now how many Jag fixes can do that?” Copied from
Help For The Jaguar XJ-S Owner by Kirby Palm Updated: May 21, 2009

Although I have a 1991 MY. I was figuring it was the same. Also the “T” in the VIN# should have been a “Y” sorry for the typo!

Electrical guide XJ-s 1990/1991 MY publication S-57/90. Page 58 shows a brake warning inverter relay

There’s your problem the XJ-s and XJ40 are different animals. The S57 is of no use on the XJ40 as far as I am aware.

That’s OK - it simply means that your car has a “passive seat belt” as fitted to 89 - 93 models XJ40.