Classic cars forum & vehicle restoration.
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| Do you like or dislike the new dashboard ? |
| Yes I do like the new dashboard |
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100% |
[ 7 ] |
| No I do not like the new dashboard |
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0% |
[ 0 ] |
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| Total Votes : 7 |
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Ray White
Joined: 02 Dec 2014
Posts: 7210
Location: Derby
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 Posted: Tue Nov 25, 2025 2:05 am Post subject: |
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An order (Ebay) for a pair of square profile U bolts failed to arrive; indeed, the whole episode has been a fiasco ...so today I selected four 3/8" x 4 1/2" Whitworth bolts and nuts from my reserves.
I intended to mount the base plate for the pump to the chassis with the two square profile U bolts; thus avoiding having to drill any holes in it. I will now attempt a similar mounting by using nuts, bolts and two small steel plates (to straddle the chassis rail.)
I have also stumbled across a dilemma. On reading the instructions that came with the kit, it seems the electric vacuum pump requires an ignition switched power source.
My initial idea was to take a feed from the brake light switch but as that works off the battery - and not the ignition - it would mean the servo could come on with the ignition switched off.
One solution would be to swap the feed wire on the RF95 control box to the ignition side ,,, but that would apparently be unsafe and illegal.
I think I shall have to take a wire from the ignition terminal (on the control box ) and feed it through the chassis to the pump switch that is located behind the seat.
Alternatively, I could go from the fuse box but that is even further away...and besides; the kit has it's own fuse and relay.
This exercise is mainly trial and error...mainly error.  |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4264
Location: South Cheshire
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| Posted: Wed Nov 26, 2025 9:33 am Post subject: |
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| Ray White wrote: | | One solution would be to swap the feed wire on the RF95 control box to the ignition side ,,, but that would apparently be unsafe and illegal. |
Why? Brake lamps are normally on the ignition side . |
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Ray White
Joined: 02 Dec 2014
Posts: 7210
Location: Derby
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| Posted: Wed Nov 26, 2025 10:17 am Post subject: |
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| ukdave2002 wrote: | | Ray White wrote: | | One solution would be to swap the feed wire on the RF95 control box to the ignition side ,,, but that would apparently be unsafe and illegal. |
Why? Brake lamps are normally on the ignition side . |
That's what I thought. If we are right, the error is with Google. So much for A.I. 
Thank you Dave. I have checked the car and the wiring diagram....and my brake light switch IS on the ignition side (i.e. after the ammeter) so I can leave the vacuum pump connected to it after all.
A.I. stands for absolute idiocy. |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4264
Location: South Cheshire
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| Posted: Wed Nov 26, 2025 11:18 am Post subject: |
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| Ray White wrote: | | ukdave2002 wrote: | | Ray White wrote: | | One solution would be to swap the feed wire on the RF95 control box to the ignition side ,,, but that would apparently be unsafe and illegal. |
Why? Brake lamps are normally on the ignition side . |
That's what I thought. If we are right, the error is with Google. So much for A.I.
Thank you Dave. I have checked the car and the wiring diagram....and my brake light switch IS on the ignition side (i.e. after the ammeter) so I can leave the vacuum pump connected to it after all.
A.I. stands for absolute idiocy. |
One thing that I would check is that the brake circuit wiring is beefy enough to supply the inductive load that a pump will demand? and when the brakes are applied the pump load doesn't cause the brake lamps to dim or flicker. |
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Ray White
Joined: 02 Dec 2014
Posts: 7210
Location: Derby
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| Posted: Wed Nov 26, 2025 3:40 pm Post subject: |
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| ukdave2002 wrote: |
One thing that I would check is that the brake circuit wiring is beefy enough to supply the inductive load that a pump will demand? and when the brakes are applied the pump load doesn't cause the brake lamps to dim or flicker. |
The wire I am using has a diameter of 2.8mm (6mm2) which should be plenty big enough. It goes from the brake light switch to the vacuum pump switch. What I can't control, however, is the wire that goes from the control box to the brake light switch as it is built into the loom. It looks like ordinary lighting wire so I can only hope it will be enough. |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4264
Location: South Cheshire
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| Posted: Wed Nov 26, 2025 4:36 pm Post subject: |
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| Ray White wrote: | | ukdave2002 wrote: |
One thing that I would check is that the brake circuit wiring is beefy enough to supply the inductive load that a pump will demand? and when the brakes are applied the pump load doesn't cause the brake lamps to dim or flicker. |
The wire I am using has a diameter of 2.8mm (6mm2) which should be plenty big enough. It goes from the brake light switch to the vacuum pump switch. What I can't control, however, is the wire that goes from the control box to the brake light switch as it is built into the loom. It looks like ordinary lighting wire so I can only hope it will be enough. |
Most looms will use 14/0.30, 1.0mm, 8.75A cable for brake lamps circuits, the brake lamps will consume around 3.5A, if the vacuum pump is more than 60W, you would exceed the wiring rating. If the pump is over 100W it would be a non starter, as the pump on its own will exceed the cable rating. |
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Ray White
Joined: 02 Dec 2014
Posts: 7210
Location: Derby
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| Posted: Wed Nov 26, 2025 7:29 pm Post subject: |
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Dave. The 12 volt vacuum pump motor has no markings on it so I don't know the wattage. Also, there is no mention of wattage in the fitting instructions. With the typical pump rated at between 40 and 70 Watts, I would have thought there would have been more information.
I can see me taking the heavier wire directly from the RF 95 control box to the pump; thus avoiding the risk of compromising the brake light circuit. |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4264
Location: South Cheshire
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| Posted: Thu Nov 27, 2025 8:03 am Post subject: |
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A new cable would be the safer option, whilst neither the pump or the brake lamps would be on constantly, at best when they are both on I could imagine a voltage drop on the supply cable, which clearly would impact the efficiency of both the lamps and the pump.
If you measure the current draw of the pump "under max load" it would help make the decision |
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Ray White
Joined: 02 Dec 2014
Posts: 7210
Location: Derby
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| Posted: Thu Nov 27, 2025 12:13 pm Post subject: |
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I have decided to have a separate supply. It may not be as convenient but at least it will give me peace of mind. A 10 amp fuse in a plastic case came with the kit so I shall mount it and the relay in a convenient but discreet location.
Last night I fabricated two steel plates; each with 2 x 3/8" holes to take the 4 long bolts that will clamp the base plate to the chassis. After painting, I should be able to fit the vacuum pump to the car. |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4264
Location: South Cheshire
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| Posted: Fri Nov 28, 2025 6:06 pm Post subject: |
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| Ray White wrote: | I have decided to have a separate supply. It may not be as convenient but at least it will give me peace of mind. A 10 amp fuse in a plastic case came with the kit so I shall mount it and the relay in a convenient but discreet location.
Last night I fabricated two steel plates; each with 2 x 3/8" holes to take the 4 long bolts that will clamp the base plate to the chassis. After painting, I should be able to fit the vacuum pump to the car. |
I think thats the best option, don't fit a relay as it will just be superfluous . |
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Ray White
Joined: 02 Dec 2014
Posts: 7210
Location: Derby
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| Posted: Fri Nov 28, 2025 6:32 pm Post subject: |
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I think thats the best option, don't fit a relay as it will just be superfluous .[/quote]
The kit incudes a relay. There are clear instructions for wiring it so I should be O.K. 
I have established that the pump runs at 6 amps so I have bought some new 17 amp cable (red braided) and taken it from the ignition side of the control box. |
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