Hey Guys:

My truck is a '86 F250 with 6.9 diesel, (underneath of cab rotted beyond repair) and I've found a cab from a '89 F350 7.3 diesel. What's my best plan regarding the wiring harness? The '89 cab has been cut up fairly badly and I'm wondering if it's best to try and use my old dash and harness? thanks!

 

They are very different ... Anythings possible though.

-Enjoy
fh : )_~

 

i deleted the entire stock harness and installed this.
everything works now. only complaint was the rear light harness was too short.
Speedway Universal 22 Circuit Wiring Harness - Free Shipping @ Speedway Motors

 

By "cut up fairly badly" you mean the wiring is a mess?

Regardless of that, my short answer is to use your old dash and harness which seems like more work but LESS frustration.

Otherwise here are my thoughts:

I know quite a bit about electrical but not much about a conversion like this although I've looked at both harnesses, one from my 87 F250 with a C-6 (similar to your 86) and an 89 F350 with an E4OD, the latter of which has a 'Brain Box' controller for the transmission behind the Left (driver's side) kick panel. That box has about 24-26 wires that go through the firewall and into the main harness in the engine compartment. A dash from an E4OD truck might make the wiring and pin configuration from that dash to the main harness plug on your 86 a bit more complicated to sort out if you want to use the 89 F350 dash. Aside from that there will probably be several differences in the 89 F350 dash wiring but it could be sorted out to make it work.

What transmissions do these trucks have?

If faced with the same issue, my first thought was that I would not want to go through the work involved in swapping the dash and that it would (I thought) be easier to identify and trace the wiring from the 89 F350 dash to the main harness connector on the firewall and match the pin configuration to the old harness connector and try to likewise accommodate for a few differences in the 89 wiring. I would want to use the 86 engine harness with the 89 dash/wiring. That sounds simpler than changing the dash, I thought (at first). I would also replace the old style glow plug controller with the newer style solid state controller, but back to the harness.

Looking at the harness in my 87 Shop manuals (on CD) - which should be very similar to your 86 except for the solid state glow plug controller, and very similar to 87-91 diesel trucks without the E4OD, I found that the main harness connector at the firewall is not even shown. The image was unavailable at the time the original 87 shop manuals were printed in about July of 1986. I don't think it showed a pin configuration but that might be in one of the other 5 manuals. I don't have any information on the 89 harness to compare it with anyway, which would be necessary to figure out how to make the 89 dash wiring work with the 86 engine harness, match the right wires to the right pins and maybe a few changes under the hood.

I did notice a couple of differences - the dual wheel trucks had an extra connector with a couple of wires coming from the engine harness and I don't know what those are for. Secondly, a factory tow package harness if either truck has one. Maybe a couple of other differences, like a throttle position sensor and transmission sensors- not sure what the ZF 5 has.

All of that being said, if a person is knowledgeable enough and comfortable determining and sorting out the differences in wiring and sensors then using the 89 dash is probably not that difficult to do.

On the other hand, using your 86 dash and fuse panel (only if that fuse panel is wired differently than the 89) would be pretty much free from wiring confusion and related problems that might occur before it's finally right.

Other people here have swapped dashboards, I think Idiot has, he made it seem like a routine job done in a day with no problems mentioned. (I can't do work like that anymore) I think I've read where people have done it the other way while posting questions about wiring and components.

Swapping the dash seems to me, to be more work but avoids the mental work and stress/frustration of figuring out the wiring and getting everything to work right.

Lastly you could hope to find a good cab from an 86 or 87 - only difference I know of in the 87 is the solid state glow plug controller.

For a better chance to find a good rust free cab you might have to travel out of the 'Salt Belt' and the closest states to Massachusetts that don't use a lot of salt on the roads during winter months are Kentucky, Tennessee and North Carolina. Better still the hot arid states of the Southwest.

Salt Belt States:

http://en.wikipedia.org/wiki/Salt_Belt"

OR, you could just patch up the cab you have while trying to make it easy and inexpensive. I grew up in the Rust Belt and I've never been afraid of rust. "Rusted beyond repair" is a very relative concept. For one person it may be viewed as a complete loss but for another person it's a viable restoration project. At least the truck is not a rare species so you can find better cabs and that's easier than fully restoring one that is rusted out.

 

Many thanks to all of you! Especially FixnStuff for your time and thorough reply, covering a lot of aspects of this issue What you said pretty much confirms my gut feeling that swapping the dash is my way to go. I'm not that knowledgeable with electrics, but making the old dash fit into the new cab is something I'm not (too) afraid of...

Also, I hear you about rust... but I have this new cab and think I'll give it a go...probably keep the old one, repair it.
Transmission: the 86 is 4wd 4speed manual hi & low. 89 is automatic. Also, the 86 is a 'camper special' has wiring for trailer brakes, option for dual wheels etc.

by 'cut up fairly badly' I mean some things were cut to facilitate removal from the chassis, and I just don't know what everything is at this point.

IDIoit - I looked at that harness, one of the features is a plug to GM column, would that be just irrelevant, or could it be a problem?

thanks again all; great help! Can't start for some days or weeks but I'll keep posted!

 

I just mentioned you in the post I was writing while you posted.

Are you suggesting that this is an easy way for the OP to use the 89 F350 7.3L dash in his 86? I can see that deleting the respective old main harness connectors at the firewall (and the engine harness) would eliminate that wiring confusion.

1) Do you think that the instructions that come with that aftermarket harness are adequate to wire the 89 dash to the 86 truck? (Seems simpler than what I was thinking!)

2) Would he have to remove the 89 dash to install this aftermarket harness? I don't have time to read the installation .pdf) In that case he could chose to use the 86 harness already in the truck and only have the extra work of removing the old dash from the original cab.

I don't know how much work it takes to remove the 86 dash and "What If" a couple of the mounting locations are different?????

1987-91 was a significant design change (to 8th generation as I recall) and much of that change was INTERIOR. If the mounting locations of the dash changed that would be something to cuss about after doing that much work to swap the 86 dash into the 89 cab.

If the aftermarket harness will largely solve the problems related to the differences in harness wiring then I think I would prefer to spend the money on that aftermarket harness and use the 89 dash. Being on LOW income Social Security I always compare the options of more work (spending less money) vs spending more money for less work. I would have to save money for 2 whole months to buy that harness but in this case I would be tempted to do that - especially if I wanted to keep the 89 dash.

I remember seeing the photo you posted after you completed installing a dash in one of your trucks but I don't remember if it was a different dash or the same one that was in the truck.(?) I guess I had assumed that it was a different dash.

 

johnny, the harness does come with the GM style column wiring.
which is nothing more than the GM pins on the end of the wires.
and 2 different pin blocks. both of which i did not use.
all signals have the same amount of wires, hazard, brake switch power, left and right signals. and a few others i know i missed.
i simply cut the pins off and soldered/shrinkwraped to my ford pig tail.
everything went like clockwork, save 1 glitch, i installed the incorrect wire to the brake power "in" which was easily remedied.

now one of the biggest chores of this job would be to wire in the stock dash.
not all that hard, just time consuming.

the directions that come with this cheap a$$ kit are pretty vague. it will outline things like ignition switch, column wiring, and charging.
having the wires individually labeled helped more than their instructions.
i did use the ford electrical and vacuum troubleshooting manual quite a bit. and became so intimate that the pages started sticking together by the end of the job.

i did use a different dash. my truck is an 87, and i used the OBS dash. 96 gasser dash specifically (what else are post 72 gasser trucks good for besides parts?)
this dash swap i did do in a weekend. but it was just the mounting. this was the 2nd time i had done the swap.
the first time i was using a PSD dash, so the PSD harness was retained.
on my dash, i actually installed a "mock up" dash i got from the junkyard.
i had a super clean dash from a 96 gasser i cut up and i didnt want to weld around it.

i did pull and gut the gasser dash, found all the wires i needed for the HVAC, and interior lights.
ran them nice and clean leaving the power wires and ground wire exposed so that i could connect them when i was ready.
i did spend a week and a half wiring it all up, mainly because i was using a keyless entry harness and trying to wire off a "without keyless entry" diagram LOL
after i unfukt myself, it went alright...

now, im no expert, but i do have lots of experience in wiring. ive done probably 15 cars with different types of harnesses. and this one is my favorite.
mostly for my jewish wallet.

i have no clue about the differences inbetween the bull nose and the brick. ive only owned 1 bull nose and it was used for parts.
but, 87 F600's did come with the bull nose dash, perhaps they are not too dissimilar

the wiring on these are not that tough. well, compared to a 66 Cadi with as many vacuum lines as wires

think i answered most of the Q's if i missed something let me know.

 

Thank you, johnny19. I saw later that you had posted the same in an old topic which didn't get a reply and I think you did right by starting a new topic. Having read that other topic I see that the 1987-1991 style change did affect the dash mounting but that the change is fairly easy to correct to install your old dash in that newer cab.

IDIoit, that is one heck of a good post and some very impressive work. Thanks for taking the time to explain all of that.

 

Thanks again Fixn & Idiot! I really appreciate the time and knowledge that went into those replies - I'm keepin my fingers crossed and gonna go ahead with this hopefully soon and will keep you guys posted

 

OK finally making a little progress here. (can only work on it in my "spare time" LOL) Question of the day is: how do I disconnect the steering column? Is there a video or photo somewhere that can help me identify what needs to be disconnected? Thanks, Johnny