|
|
| Author |
Message |
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
 Posted: Sun Dec 07, 2025 7:16 pm Post subject: positive earth question. |
 |
|
My vacuum pump instructions only refer to a negative earth. As my car is positive earth, should I swap the wires to the pump motor?
Also what about the relay and switch?
I would greatly appreciate some help to avoid making an expensive error.
Please click on link for fitting instructions and diagram. Thank you.
https://www.carbuilder.com/cdn/shop/files/Vacuum_Pump_Instructions.pdf?v=17357643397575415403
 |
|
| Back to top |
|
 |
ukdave2002
Joined: 23 Nov 2007
Posts: 4284
Location: South Cheshire
|
| Posted: Sun Dec 07, 2025 9:07 pm Post subject: |
|
|
| All you need to do is reverse the pump connections, so the red pump wire goes to 5 and the black to 2. Everything thing else stays the same, unless the relay has a diode built in, in which case swap 1 & 2 (relay coil ) around. |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Sun Dec 07, 2025 10:48 pm Post subject: |
|
|
| ukdave2002 wrote: | | All you need to do is reverse the pump connections, so the red pump wire goes to 5 and the black to 2. Everything thing else stays the same, unless the relay has a diode built in, in which case swap 1 & 2 (relay coil ) around. |
Thanks Dave. That has really helped me. I don't see a diode symbol on the relay so I presume it is not there. |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Wed Dec 10, 2025 3:17 pm Post subject: |
|
|
| So I wired everything up as directed and...nothing. I found the 10 amp fuse had blown. What I don't know is if this happened before or after the "switch on". I can't go further at the moment as I have discovered the blade fuse is physically half the size of the ones I have. |
|
| Back to top |
|
|
ukdave2002
Joined: 23 Nov 2007
Posts: 4284
Location: South Cheshire
|
| Posted: Wed Dec 10, 2025 6:01 pm Post subject: |
|
|
| Is the relay electronic ? Or definitely doesnt have a diode? |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Wed Dec 10, 2025 7:32 pm Post subject: |
|
|
| ukdave2002 wrote: | | Is the relay electronic ? Or definitely doesnt have a diode? |
How would I find out, please? |
|
| Back to top |
|
|
ukdave2002
Joined: 23 Nov 2007
Posts: 4284
Location: South Cheshire
|
| Posted: Wed Dec 10, 2025 8:58 pm Post subject: |
|
|
| Is there a part number on it? Or can you pop the cover off? Thinking about it, the last time I saw a relay with those terminal numbers it was an electronic delay relay used to hold vehicle internal lamps on for about 10 seconds after the door was closed. If it is an electronic device and has the incorrect power polarity, it could well explain why the fuse has blown, as would a simple diode across the coil, it is effectively a short circuit. |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Thu Dec 11, 2025 12:00 am Post subject: |
|
|
| ukdave2002 wrote: | | Is there a part number on it? Or can you pop the cover off? Thinking about it, the last time I saw a relay with those terminal numbers it was an electronic delay relay used to hold vehicle internal lamps on for about 10 seconds after the door was closed. If it is an electronic device and has the incorrect power polarity, it could well explain why the fuse has blown, as would a simple diode across the coil, it is effectively a short circuit. |
So...would it be safe to swap 1 and 2 ? |
|
| Back to top |
|
|
ukdave2002
Joined: 23 Nov 2007
Posts: 4284
Location: South Cheshire
|
| Posted: Thu Dec 11, 2025 11:20 am Post subject: |
|
|
| Ray White wrote: | | ukdave2002 wrote: | | Is there a part number on it? Or can you pop the cover off? Thinking about it, the last time I saw a relay with those terminal numbers it was an electronic delay relay used to hold vehicle internal lamps on for about 10 seconds after the door was closed. If it is an electronic device and has the incorrect power polarity, it could well explain why the fuse has blown, as would a simple diode across the coil, it is effectively a short circuit. |
So...would it be safe to swap 1 and 2 ? |
Do a simple continuity test between 1 & 2, then reverse the meter connections, if you get continuity one way but not the other then its a solid state device of some sort, either diode protected relay or a more complex electronic timer. |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Thu Dec 11, 2025 12:37 pm Post subject: |
|
|
| I have been to look at the relay. It has a number: 28146RE. If that helps?" |
|
| Back to top |
|
|
ukdave2002
Joined: 23 Nov 2007
Posts: 4284
Location: South Cheshire
|
| Posted: Thu Dec 11, 2025 1:04 pm Post subject: |
|
|
| Hi Ray its a timer, that will have some solid state switching, this will be why the fuse blew, swap 1 & 2 round and it should resolve the problem. |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Thu Dec 11, 2025 2:16 pm Post subject: |
|
|
Dave. Many, many thanks.  |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Sat Dec 13, 2025 4:17 pm Post subject: |
|
|
Wires swapped over on the relay and a new 10 amp fuse fitted ...and still nothing.
The fuse has not blown.
I am at a loss to know what to do now!  |
|
| Back to top |
|
|
alastairq
Joined: 14 Oct 2016
Posts: 2143
Location: East Yorkshire
|
| Posted: Sat Dec 13, 2025 5:21 pm Post subject: |
|
|
Is the pump insulated from the vehicle's ground? IE, is it completely insulated from the chassis, not touching any part of the vehicle with the pump body?
I'd be removing the pump itself, then seeing if it works away from the car, with those wires reversed?
In other words, it's possible the pump body and bracket are earthed to the pump, as it comes?
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces. |
|
| Back to top |
|
|
Ray White
Joined: 02 Dec 2014
Posts: 7270
Location: Derby
|
| Posted: Sat Dec 13, 2025 9:47 pm Post subject: |
|
|
| alastairq wrote: | Is the pump insulated from the vehicle's ground? IE, is it completely insulated from the chassis, not touching any part of the vehicle with the pump body?
I'd be removing the pump itself, then seeing if it works away from the car, with those wires reversed?
In other words, it's possible the pump body and bracket are earthed to the pump, as it comes? |
I have mounted the pump exactly as per the instructions. There are four securing screws holding rubber mounts to the chassis. Perhaps they could short the motor if it was not insulated ...but I would be surprised if it wasn't...and I expect Car Builder Solutions would have had complaints if the kit was no good. |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Profile
Log in to check your private messages
Log in
