No 1st gear and not shifting down - computer gov?

[bytes311]

Driving down the highway, the car started shifting up and down like it didn't know which gear to shift into. It corrected itself after I let off the gas, but then suddenly it stopped shifting all together and stayed in 1st.

I looked over the governor for bad solder joints and blown caps but nothing stood out. I replaced the two transistors with TIP42C anyway and put it back together to see if that was the problem. In drive, it goes 1-2-3 like it should, but now it won't down-shift coming to a stop. It stays in either 2nd or 3rd. I tried to manually shift it over to 1st but it made no difference.

Does this sound like a failing computer governor? I measured the resistance of each solenoid at approx 40 ohms, but I heared they should actually be 25 ohms.

Short of buying a $300 replacement computer, I'm at a loss. Any guidance would be appreciated.

[David T]

Driving down the highway, the car started shifting up and down like it didn't know which gear to shift into. It corrected itself after I let off the gas, but then suddenly it stopped shifting all together and stayed in 1st.

I looked over the governor for bad solder joints and blown caps but nothing stood out. I replaced the two transistors with TIP42C anyway and put it back together to see if that was the problem. In drive, it goes 1-2-3 like it should, but now it won't down-shift coming to a stop. It stays in either 2nd or 3rd. I tried to manually shift it over to 1st but it made no difference.

Does this sound like a failing computer governor? I measured the resistance of each solenoid at approx 40 ohms, but I heared they should actually be 25 ohms.

Short of buying a $300 replacement computer, I'm at a loss. Any guidance would be appreciated.

Go over all of the solder joints. Reheat them and make sure they flow. You didn't have to replace the output transistors, if they were bad you would not get 1st or second at all. If you get them intermittently it is because of the caps or bad solder joints. Same for the shift solenoids. I would also flush the transmission fluid,clean the filter and check all of the external adjustments. Make sure the wiring is secured away from the hot exhaust pipes. Make a light box and you can see what gear the shift computer is commanding the transmission to be in. Get the RPM vs MPH chart so you can see what gear you are in also.

[hmcelraft]

If you are going to test your computer work I would get a piece of rubber hose and a drill to turn the computer generator, make up a wiring harness to show which gear the computer is in and bench test it. The trans can get seriously damaged with a faulty computer. If you have first and second your solenoids are fine - they rarely go bad.

The trans shifting computer can usually be fixed but, some of them are a bigger mess than others to clean and find the wiring problems. $300 isn't actually a bad price to assure you won't ruin your trans. I've seen an auto trans get really screwed up with a bad 3-1 down-shift at highway speed.

[dmruschell]

This may sound stupid, but did you check the transmission fluid level? Low transmission fluid can cause it to shift strangely, and to not want to shift into 1st when stopped.

[Elvis]

I'm such a big fan of repating...


RESODLER EVERYTHING !!!

and before you can do that - you have to scratch off the conformal coating off the solder joints
or it won't solder correctly even if it looks like it does.

Where do I know from ?

well, I paid for this experience !

Of course you should apply new conformal coating afterwards.


I made new PCBs with the same schematic but with vias that withstand much more force and vibrations
than single sided copper PCBs.
All my governors are tested before they leave my desk, all of them are within +-0.1V of the average
shifting voltages.

Have fun scratching the yellowish stuff off :-)

[Bitsyncmaster]

RESODLER EVERYTHING !!!

and before you can do that - you have to scratch off the conformal coating off the solder joints
or it won't solder correctly even if it looks like it does.

+1
What works pretty good to get the conformal coating off is to use solder wick and your soldering iron on every joint. It's basically unsoldering every part to resolder.

[PJ Grady Inc.]

I've never seen low fluid cause a no low 1 condition. That is usually a bad computer condition but there are a couple other possible but unlikely causes. What low fluid will cause is slippage especially when cold which will destroy the transmission in short order. Never drive with low fluid if it can be avoided.
Rob



This may sound stupid, but did you check the transmission fluid level? Low transmission fluid can cause it to shift strangely, and to not want to shift into 1st when stopped.

[vps3922]

I had the same issue and it was the governor. I still have it and the capacitors on it are dry and bulged. The uncertainty of the computer in which gear it should be is the first sign of the failing of it. I replaced it with the mentioned $300 digital governor from DMCH and it works like a charm. The old governor circuits are fine but the capacitors look scary.

[dmruschell]

I've never seen low fluid cause a no low 1 condition. That is usually a bad computer condition but there are a couple other possible but unlikely causes. What low fluid will cause is slippage especially when cold which will destroy the transmission in short order. Never drive with low fluid if it can be avoided.
Rob

I've got a freshly rebuilt automatic that has been badly leaking fluid for the last 2.5 years. I just haven't gotten around to fixing it. At this point, I don't know if I even remember where DPI Josh said the problem was. But, Rob, you'll see it at the Spring Social in May, so maybe you can refresh my memory :)

I guess I should clarify: When the fluid got low, it wouldn't go into 1st gear at a stop. When I would press on the gas to start moving, it would initially be in 2nd gear (and slipping) for a split second before downshifting into 1st gear.

[Delorean Industries]

I want to say it was the shift cable...

[dmruschell]

I want to say it was the shift cable...

I kept the paper from the tech inspection last year, and I know where I saw it last. Unfortunately, that was several months ago. With the lady liking to keep things clean, I have no idea where it might be now. Fortunately, I remembered everything on the list except the specifics of the transmission leak lol.

[David T]

I've never seen low fluid cause a no low 1 condition. That is usually a bad computer condition but there are a couple other possible but unlikely causes. What low fluid will cause is slippage especially when cold which will destroy the transmission in short order. Never drive with low fluid if it can be avoided.
Rob

If the fluid is low enough to cause problems you will get no 1st gear. You won't get ANY gear! If it is borderline you may get a little but as Rob says, it's going to be slipping a LOT and very quickly, again, you will have NO gears. Whenever you have an issue with the automatic transmission one of the first things you should do is check the fluid level and condition. Especially if you KNOW it is leaking. Don't forget, on the automatic you have to separately check the final drive level.

[bytes311]

Thank you all for your replies. I made several attempts at repairing the board myself, but I finally gave up after burning through a couple traces. A friend of mine repaired the traces and the car shifted from what felt like 2nd to 3rd, but only once. I think it's stuck in 2nd now.

I have the governor in a shipping box ready to get it replaced with a digital computer as suggested. Do I just call the DeLorean store hotline and tell them I need a digital computer governor?

[David T]

Thank you all for your replies. I made several attempts at repairing the board myself, but I finally gave up after burning through a couple traces. A friend of mine repaired the traces and the car shifted from what felt like 2nd to 3rd, but only once. I think it's stuck in 2nd now.

I have the governor in a shipping box ready to get it replaced with a digital computer as suggested. Do I just call the DeLorean store hotline and tell them I need a digital computer governor?

Call your favorite Delorean vender and discuss your options. It may work out that they can repair your old one or trade it in towards another. Digital is not the only way to go.

[DMCMW Dave]

Call your favorite Delorean vender and discuss your options. It may work out that they can repair your old one or trade it in towards another. Digital is not the only way to go.

Except now he's told everyone he smoked the boards in the core. The DMCH et. al. digital ones don't care as the boards get replaced, but the "rebuild" analog options still need the original boards.

[bytes311]

The way the board is now, I think I have no other choice but to go digital. At least I won't have to worry about it once it's done.

So who do I need to contact at DMCH to make that arrangement? I've never purchased anything off their site before.

[DMCMW Dave]

The way the board is now, I think I have no other choice but to go digital. At least I won't have to worry about it once it's done.

So who do I need to contact at DMCH to make that arrangement? I've never purchased anything off their site before.

You should call either DMC California (since you are there) or Texas. Typically you take it off you car, send it in, and get the same one back with new internals. They will tell you shipping instructions and invoicing. This is not something I'd try to order online. Talk to a human.

[bytes311]

Thanks Dave. I forgot all about DMC California. I will do that!