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AC help needed. Wiring diagram?

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AC help needed. Wiring diagram?

Postby DownUnder » Mon Jan 17, 2022 2:17 am

Hi folks,

both my AC compressor and fans don’t come on with the AC switch on the fan speed control knob. If I connect the compressor positive connection straight to battery positive it does spin and the condenser becomes hot. I’ve just had it regassed after fixing a leak on the condenser and the auto electrician said it worked all fine and blew cold air. The only issue they said is that the system is running at very high pressure in idle hence i should only use it on the highway which is fine with me (I suspect the viscous fan needs a rebuild or the two additional fans don’t come on).

What I’ve checked is the following;

- both the high pressure and low pressure switch let current through. If I put a bridge on both plugs it makes no difference, compressor still stays off.
- 30-A fuse is fine
- AC light comes on with the switch. Fan only blows at full speed setting (speed resistor but that shouldn’t have an influence?)
- couldn’t find a designated relay for the compressor in the fuse box

I hope someone could point me in the right direction. It is a bit frustrating as I’m driving around Outback Australia in the summer now. Does anyone have a wiring diagram? I couldn’t find one online or in the Haynes manual.

Thanks in advance.
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Re: AC help needed. Wiring diagram?

Postby DownUnder » Mon Jan 17, 2022 3:09 am

I was going to replace the fan speed resistor too. Spare parts seem a bit scarce here, anyone know the part number for a Mk5 resistor? Will a Mk6 and Mk7 resistor fit a Mk5?
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Re: AC help needed. Wiring diagram?

Postby MinorMatt » Mon Jan 17, 2022 10:14 am

I have wiring diags somewhere, but I will have to find them.

There are variants of resistors on smileys dependant on age - so how old is yours?
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Re: AC help needed. Wiring diagram?

Postby Kyzza » Mon Jan 17, 2022 11:17 am

Hey Down under, if you've got the newer model mk5 (Mines a 00 model) I replaced my resistor last year with the part number '3C1H18B647AA' this one is located in the dash behind the blower motor. If you've got the older model (pre 97?)/which has a resistor next to the headlight, I can check the part number for you tomorrow.

Would love to see a wiring diagram as I've just rewired some of my aircon loom ready to be regassed. I'm hoping my wiring is correct but couldn't find a diagram here in Aus. Copied the wiring of my parts van.

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Re: AC help needed. Wiring diagram?

Postby DownUnder » Mon Jan 17, 2022 10:29 pm

I believe it it the newer version of the Mk5, built in 1997. the VIN is WFOLXXBDVLVP55197

If you could find those diagrams that would be great. Any idea where the compressor relay would be located?
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Re: AC help needed. Wiring diagram?

Postby Altransit » Mon Jan 17, 2022 11:31 pm

DownUnder wrote:I believe it it the newer version of the Mk5, built in 1997.

My mid year '97 had the resistor next to the headlight (UK drivers side H/L)
1994 Mk4 SWB 115 Minibus 70ps Di (R.I.P.)
1997 Mk5 SWB 115 Minibus 70ps Di (Gone, but not forgotten!)
2004 Mk6 SWB T280 Medium Roof 85PS 2.0 TDDi - Vantunered (Also gone)
2008 Mk7 SWB T280 Medium Roof 85PS 2.2 TDCi - Also Vantunered
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Re: AC help needed. Wiring diagram?

Postby DownUnder » Tue Jan 18, 2022 11:33 am

As for the wiring it shouldn’t be too complicated really, I assume it would be battery positive to fuse to relay (switched by the internal switch) to low- and high pressure switch and then parallel to both the fans and the compressor, all of which are grounded. Would there be any additional flow or temperature sensor in there? How did you do it, Kyzza?
And cable colors would be of interest of course.
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Re: AC help needed. Wiring diagram?

Postby Kyzza » Tue Jan 25, 2022 9:36 am

Apologies @DownUnder, have started a new job delivering parts to all the local mechanics and have been super busy, still haven't made it out to check on my older model Transit as I've also been having some timing issues with my newer model. Will try make it out there ASAP.

However I do believe Alttransit is right. 97 models have the older resistor and I believe the part number may be 95VB18591AB. Take a look down the side pillar between the radiator and drivers side headlight and you should see the part. I am trying to work out what all the colours were for the aircon wiring as the wiring is now protected in split tubing again. I should mention I only had to replace the wiring in the engine bay and the potentiometer switch for temperature control to get my AC working... Still waiting on the new accumulator before getting my system recharged.
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Campervan: 2000 Transit VG MK5 - 2.5 Di -85ps - Auto - LWB
Cab Chassis: 1999 Transit VG Mk5 - 2.5 Di - 100ps - Manual - LWB
"Spare Parts Van" 1997 Transit VG Mk5 - 2.5 Di - 100ps - Manual - SWB
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Re: AC help needed. Wiring diagram?

Postby DownUnder » Tue Feb 08, 2022 8:20 am

Kyzza wrote:
However I do believe Alttransit is right. 97 models have the older resistor and I believe the part number may be 95VB18591AB. Take a look down the side pillar between the radiator and drivers side headlight and you should see the part.


Many thanks, I found the part just there and ordered a new one.

The problem seems to have shifted a bit now as the blower doesn’t go at full speed any more but works in setting 1 and 2 at quite a low speed. And then sometimes the aircon does come on. Very strange… Will keep you posted whether the new resistor would fix the aircon issue as well.
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Re: AC help needed. Wiring diagram?

Postby MinorMatt » Wed Feb 09, 2022 9:05 am

DownUnder wrote:
Kyzza wrote:
However I do believe Alttransit is right. 97 models have the older resistor and I believe the part number may be 95VB18591AB. Take a look down the side pillar between the radiator and drivers side headlight and you should see the part.


Many thanks, I found the part just there and ordered a new one.

The problem seems to have shifted a bit now as the blower doesn’t go at full speed any more but works in setting 1 and 2 at quite a low speed. And then sometimes the aircon does come on. Very strange… Will keep you posted whether the new resistor would fix the aircon issue as well.


If it works on 1 and 2, but not 3 that is either faulty wiring or a faulty switch... it won't be the resistor
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