Suburban central locking

[Jermu97]

Hi,

I have a bit of a problem with my door locks I can't seem to figure out. The truck is a 1989 Suburban and the central locking doesn't work on the rear doors. The rearmost panel doors work, not too great, but work either way, that's just old age. But apparently when the truck was registered for a lower weight class, as a "van" it was illegal to have central locking on the rear side doors. As such they've been rendered useless, but I can't find where... The wire connectors are attached at the pillars and inside the doors, as well as in the front. I have yet to test the volts at said connectors, but I doubt the problem is there. Where should I look next? I've tried to scour the inside of the dash, but haven't found anything and the manuals only show the one connectors at the pillars. I've also checked the relay at the steering column that isn't shown in the manual, but could be found in the wiring diagrams.

You must be registered for see images attach

 

[bucket]

If I'm understanding the question correctly, the rear passenger doors do not lock when either power lock switch up front is actuated? If so, testing for voltage at the connectors is absolutely the place to start. It's very likely that the power lock solenoids in the rear doors simply don't work anymore. It's very common.

Where was the truck sold new? In the states, vans are allowed to have side doors with power locks. Also, depending on the state, Suburbans get registered as all kinds of things. Ohio for example, a 1/2 ton Burb is registered as a station wagon, and a 3/4 ton Burb gets registered as a 3/4 ton truck.

 

[Jermu97]

They don't lock nor unlock from either of the front door switches. I'm pretty convinced that the actuators work, but then again as far as I know all the wires are connected, so I may be wrong. Will have to test once I get home, unless someone can tell me a location of a connection I haven't yet found.

It was sold as new in Finland. Usually a vehicle of this weight class (8600lb GVWR) is considered a light truck (3500-7500kg's), and everything below that is a passenger vehicle (8+1 passengers max) or a van (meant for hauling goods). Back in the day many normal cars and wagons were registered as vans because of taxes, even though they came with restrictions like hard backseats and manual locks on rear doors and hwat not, but it was just that much cheaper back then. This article is a great example of the lenghts people would go to to avoid taxes...

Finland's Tax Laws Gave Birth To A Surprising Number Of Camaro Trucks

Sometimes draconian tax laws are all you need to make weird cars exist

jalopnik.com

Here's an example from the modern day to put things into perspective: my first car was a Mercedes-Benz 2002 C220 CDI wagon. So a 2.1 liter turbodiesel i4. The taxes were ~650€ a year.
My next car was the 1995 C2500 with the 6.5 turbo detroit. Because of the 3900kg GVWR it was a light truck. Only restriction: 80km/h top speed (but you don't have to have a limiter on anything before the year 2001 IIRC, so it's up to you how fast you really wanna drive). The taxes are 84€ a year. These days vans have taxes almost identical to normal passenger vehicles, but back then it was more like the contrast between passenger vehicles and trucks.