RallyDogRacing

*** new updates on later pages*** Car is still not working

Hey guys - I've been living with what appears to have been a clock problem for some time because multiple attempts to reset my Airbag & Seatbelt light has resulting in it always coming on again. I was simply too lazy to resolder everything.

Well tonight I was zipping out to go get dog food and I noticed that all of a sudden I had Alt light. Crap. Checked the belt and things were spinning so I went back home. On the way back I noticed that the Speedo was behaving very oddly and barely registering (3rd gear 2k rpm, 15mph indicated). I further noted that the tacho meter was working fine accept on taking off from a dead-stop during which it momentarily drops to zero - but is otherwise unimpacted.

Once home I grabbed the DMM and checked for battery voltage with AC, Headlights and the interior fan set to "2". I had consistent 13.87v so I think my charging is good (alt and batt less than 1yr old).

So I'm thinking the root cause must be this clock because so much passes thru it electrically speaking. During it's removal from the dash I found that the large single-pin connector was barely attached to the wire and in fact the connector broke free of the wire completely just touching it. I can resolder it - so no big whoop.

My question: should I just fix that wire and put everything back or go head and
fix the solder joints on the clock's PCB just to be sure... Oh and can a cooky-crazy clock impact either speedo or tacho?

Rob Dupree - now in Houston TX
1990 C4 w/165k miles on non-rebuilt motor!

RallyDogRacing

Update: Sat AM - I bit the bullet and pulled everything apart. Followed the write-up on John's 964 website and reworked the connections of the clock. It was much less intimidating than I expected once I got rolling. Those solder suckers are pretty cool. I re-did the single-connector with the brown/green wire and re-installed everything. Fired up the car and still no instruments.

Went up to the fuse block and found #18 blown. Replaced. Refired the car and all instruments were back to normal. Even the time adjusting switch on the clock worked much better than it ever has. I still have my airbag & seatbelt lights illuminated - but per the site I probably need my mechanic to reset the code with the Hammer. I'll take it for a driver later and see if the speedo is back to normal - but I fully expect it to be.

Any Houstoner's with a Hammer who want to reset a code for me? I'll buy the beer!

jimq

Rob why dont you build one of the scantool setups and then you will have your own "hammer" to use whenever you want! It will reset and read the codes for little money. Smokin had a Scantool setup he was mailing around for people that needed it.

JasonAndreas

You can also buy an interface pre-made for $30USD.

RallyDogRacing

Well I took the car for a spin and found that fuse 18 had blown again. I'm thinking maybe I've got that problem with the hydraulic switch on the pump.

JasonAndreas

I went through the wiring diagrams for the MY90 C4 and I couldn't find where fuse #18 could be connected to a hydraulic solenoid problem. Can you post a link or page number from a book or TSB, or are you blowing fuse #15? Fuse #18 would definitely be appropriate with your gauge problems.

RallyDogRacing

The only thing that got me thinking that they were related was: https://rennlist.com/forums/showthre...highlight=fuse

And it seems that my fuse blows at roughly the same time as when my hydraulic idiot lights go out on the dash - which I presume to mean the hydraulic system is up to pressure and that switch on the pump is closing (hi pressure), or opening if it's the low-pressure one. Perhaps the listed thread doesn't apply to MY'90, but it seems like a possible cause.

So my thoughts are to replace fuse#18, and disconnect the switch on the pump and go for a 2-5min drive. If the fuse stays solid, I'll re-connect the switch and see if the problem comes back. I would assume that the hydraulic pump won't cook itself with less than 10mins of continuous run-time.

I'm totally open to other suggestions BTW.

Thanks!

Computamedic

I beleive there is mention in Adrian's book that the hydraulic pump IS likely to do exactly that after running for more than 2 minutes. I don't think I'd chance a 10 minute run with something THAT expensive!!!

Regards

Dave

RallyDogRacing

Well I'm still baffled by this. Finally got some 7.5amp fuses today plus a 10amp circuit breaker. 7.5amp jobs blow really quick. I risked putting the 10amp c/b in to get home and things worked really well. So feeling brave/stupid I took it for a longer driver.

After driving around for about an hour through Houston, some city some highway I can find no pattern to what appears to be current-draw spikes. The longer I drove the car the closer together the c/b reset intervals would be - but then inexplicably they would lengthen backout. Almost like a bell-curve, no resets for 5 miles then a few, then none.

I'm starting to wonder if my clock repair has somehow caused this problem...

jimq

maybe a wire shorts when you hit a bump and it moves???

Indycam

Disconect the pump after it has pumped up the bomb .
Drive without the brakes , save the pressure in the bomb for when you really need it .
Do you still pop a fuse ?

If while you are driveing , the pedal goes hard , hook up the pump again .

RallyDogRacing

IndyCam - did as you suggest. With Hydraulic pump power and pressure switch disconnected and a 7.5amp fuse in place the circuit blows as soon as I start to rev the car to move it forward. Repeated the test with the pumped hooked up and experienced same behavior. Re-installed circuit-breaker and it was tripping at idle every 2secs. Shut car down, re-seated circuit breaker and restartedd engine - now breaker is holding. I'm really baffled now.

So to re-cap: drove the car a few weeks ago and lost instruments & got the alt-light. Figured clock was at fault because of long-time AirBag & SeatBelt light illumination which happened after a rail-road crossing. Followed repair procedure from 964.co.uk for the clock hoping to solve both problems since the circuit board is part of both fails. After re-installation now have fuse-18 blowing constantly.

MikeFunk is going to help me find a known-good clock to try and swap to determine if it's truly the cause. But if folks surmise the problem is deeper rooted elsewhere - it might be time to head to EuroCarWerks for repair.

Rob D.
'90 C4 - 165k miles

AOW162435

Rob,
The single large connector is is for the clock adjusting mechanism. It sounds like the connector was bad for a while, which explains why it worked poorly in the past.

Keep an eye on Ebay for the 964/993 clocks - they come up every few weeks.

Andreas

dfinnegan

Rob,

I have a clock. I expect it works, but have no proof. PM me and I can post it in the morning. Then we can work out a replacement later.

Dave

RallyDogRacing

Thanks Dave - I appreciate the offer - I've currently got a person on the left-coast sending me a known-good unit for testing purposes.

Andreas - I did (for curiousity sake) disconnect the large post to see if anything changed - and the problem persisted. So I'm glad to know that the connectivity with the adjuster was related and some improvement was justified. Funny tho - now I want my cruddy clock adjustment back in exchange for Fuse-18 staying normal.

I will update this thread when the new clock comes in and I try it. Still happily taking suggestions on other points of possible root cause. Wondering if trading the car in for a 996tt would solve it...