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**kitesurf_phil** · 22 May 2005, 20:36

Originally posted by chavo

i've tried everything imaginable to try and remedy my 4wd problem, but have been unsuccessful. are there fuses for the 4wd system that if blown would prevent it from engaging? when i shift it into 4hi or 4lo i hear no click and see no light on dash. i have noticed that the shaft leading to the front diff does rotate when i move the lever, but the wheels don't. i've done resistance checks on the silenoids and found they are good, i've also checked the vaccuum lines and see no defects so i assume they are good. as far as the relays go, i've checked one of them, but can't find the rest. what would be the drawbacks of permanently locking the front axel and bipassing the ADD system altogether?

if anyone can provide any advice i would sure appreciate it. i'm getting ready to sell it and i wanna be sure the next owner gets a good deal so he can enjoy it as much as i have, and not be stuck with a junker.

Keeping the 4WD engaged full time would wind up the transmission. 1st and 2nd Gens dont have a centre diff, so the 4WD is only for the slippery stuff. Maybe TonyN could give you a sensible answer regarding the problem. Have you done a search in the technical section? I'm sure someone posted the vacuum line diagram and the electrical diagram for the ADD.

**Silversurfer** · 22 May 2005, 21:14

The attachment is a schematic for the Surf ADDS system - I have some other info but can't post it due to size restrictions. Drop me your Email and I will post it direct if you want.

Attached Files

**NiftyNev** · 23 May 2005, 00:45

Try this.Pics are a bit iffy but you get the idea.

http://www.toyotasurf.asn.au/techsite/add.htm

Neville

**chavo** · 25 June 2005, 01:33

today i did voltage checks on the vsv's to see if there was any change when i switched on the 4wd, and as i suspected there wasn't. i tried applying voltage to the vsv that engages the 4wd, but ended up with a blown fuse, so i assume that the fuse on the diagram is the dash gauages fuse. then i tried switching the vaccuum lines and to my surprise i think it engaged, but when i shifted into 4hi and 4lo the 4wd light on the dash started flicking on and off really fast. i came to the conclusion that it is the ADD relay that is busted, but can't find it to make resistance checks on it. does anyone have a picture of one or knows the exact location of it on a jap hilux surf?

**NiftyNev** · 25 June 2005, 10:39

The ADD relay is up under dash on the brake pedal support bracket.There are two relays.The one on left if I remember correctly is the ADD and the other (brown?) is for the aerial.

Neville

**chavo** · 26 June 2005, 04:13

Originally posted by NiftyNev

The ADD relay is up under dash on the brake pedal support bracket.There are two relays.The one on left if I remember correctly is the ADD and the other (brown?) is for the aerial.

Neville

thanks for the help. it took me some time to find it, for a while i thought i was overlooking something, but i took apart the entire dash and couldn't find any other relays. for some reason my ADD relay says "fuel pump relay" on it, or is it supposed to be like that? when i disconnect the relay and switch around the vaccuum hoses i can engage the actuator, but there is no power from the diff until i move the lever. if i just left my actuator engaged all the time would it eventually break since the tires rotate at deifferent speeds when turning?

**TonyN** · 26 June 2005, 20:32

Originally posted by chavo

thanks for the help. it took me some time to find it, for a while i thought i was overlooking something, but i took apart the entire dash and couldn't find any other relays. for some reason my ADD relay says "fuel pump relay" on it, or is it supposed to be like that? when i disconnect the relay and switch around the vaccuum hoses i can engage the actuator, but there is no power from the diff until i move the lever. if i just left my actuator engaged all the time would it eventually break since the tires rotate at deifferent speeds when turning?

I wouldn't give your front CV's to long to live is you leave it engaged all the time. The ADD relay says just that on it, its on the tranny tunnel, under the radio right? Unless someone thought the fuel pump relay will fit!

There are only two solonoids, the one on the t/case, which must be working if your front prop is turning (note, try and turn it by hand, sometimes the front prop will coast anyway as the front wheels turn.)

If not its the one on the front diff, that connect the two halfs on the long side drive shaft together. You won't get a 4wd light untill both are enguaged.

**chavo** · 28 June 2005, 12:33

i got some ADD relays from the junkyard and tried them all out, but there was no change. i checked to see if the vaccuum was good and it was, i got about 15-20 psi. i checked the VSV voltage again and there is a constant 13 volts on the vsv that connects the 2wd, and no matter what position the shift lever is in, the other silenoid gets no voltage. because of this i come to suspect the transfer indicator switch or the ADD indicator switch, since the problem is apperantly electrical. is the transfer indicator switch labelled "sensor relay vaccuum," connected to a 3-pin plug, and a vaccuum hose going to a silenoid attached to the engine? can i do a continuity check on this switch, and if so to what pins? if i wanted to manually engage the actuator with a vaccuum source, does the engine have to be on? what else can prevent voltage from getting to the silenoid that connects the 4wd? any advice would be appreciated.

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